Section 1 METROLOGY
STANDARDIZATION
QUALITY
Lecture 2 Metrology - the science of measurements
CERTIFICATION
1.
2.
3.
4.
5.
Essence and content of metrology.
Measurements of physical quantities.
Means of measuring equipment.
Rationing of metrological characteristics.
State system of industrial devices and means
automation.
2.1 Essence and content of metrology
Metrology - the science of measurements, methods and means of providing
uniformity of measurements and ways to achieve the required accuracy.
Metrology parts:
● scientific and theoretical metrology;
● legal metrology;
● applied metrology.
Scientific and theoretical metrology:
● general theory of measurements;
● methods and means of measurement;
● methods for determining the accuracy of measurements;
● standards and exemplary measuring instruments;
● ensuring the uniformity of measurements;
● evaluation criteria and certification of product quality.
Legal metrology:
● standardization of terms, systems of units, measures, standards and SIT;
● standardization of ME characteristics and methods for assessing accuracy;
● standardization of methods for verification and control of ME, methods of control
and certification of product quality.
Section 1 Metrology Lecture 2 Metrology is the science of measurement
Applied metrology:● organization of the public service for the unity of measures and measurements;
● organizing and conducting periodic verification of ME and
state testing of new funds;
● organization of the public service of standard reference
data and standard samples, production of standard samples;
● organization and implementation of the control service over the implementation
standards and technical conditions of production, state
testing and certification of product quality.
Interrelation of metrology and standardization:
methods and methods
execution control
standards
Metrology
Standardization
standards
to take measurements
and measuring instruments
Section 1 Metrology Lecture 2 Metrology is the science of measurement
2.2 Measurements of physical quantitiesMeasurement displaying a physical quantity by its value by
experiment and calculations using special
technical means (DSTU 2681-94).
Measurement error deviation of the measurement result from conventional
the true value of the measured value (DSTU 2681-94).
Numerical error estimates:
● absolute error
X meas X ;
relative error
100%
100%
X
X meas
reduced error γ
100% .
Xn
Measurement uncertainty estimate characterizing the range
values, which is the true value
measured value (DSTU 2681-94).
;
Section 1 Metrology Lecture 2 Metrology is the science of measurement
The result of a measurement is the numerical value attributed to the measuredvalue, indicating the measurement accuracy.
Numerical indicators of accuracy:
● confidence interval (confidence limits) of error
● RMS error estimation
ΔP;
S.
Rules for expressing accuracy indicators:
● numerical indicators of accuracy are expressed in units of measured
quantities;
● numerical indicators of accuracy should contain no more than two
significant figures;
● the smallest digits of the measurement result and numerical values
accuracy should be the same.
Presentation of the measurement result
~
X X, P
or
~
X X R
Example: U = 105.0 V, Δ0.95 = ± 1.5 V
or
U = 105.0 ± 1.5 V.
Section 1 Metrology Lecture 2 Metrology is the science of measurement
2.3 Measuring instrumentsMeans of measuring equipment (SIT) technical means for
performing measurements that have normalized
metrological characteristics.
SIT:
● measuring instruments;
● measuring devices.
Measuring instruments:
● measuring instruments (electromechanical; comparisons;
electronic; digital; virtual);
● recording means (register the signals of the measuring
information);
● code means (ADC - convert analog measuring
information in the code signal);
● measuring channels (set of measuring equipment, means of communication, etc. for
creating an AI signal of one measured value);
● measuring systems (set of measuring channels and
measuring devices to create AI
several measured quantities).
Section 1 Metrology Lecture 2 Metrology is the science of measurement
Measuring devices● standards, exemplary and working measures (for reproduction and
storage of the size of physical quantities);
● measuring transducers (for changing the size
measurand or conversion
measured value to another value);
● comparators (for comparison of homogeneous values);
● computing components (a set of computer hardware and
software to perform
calculations during the measurement).
2.4 Standardization of metrological characteristics
Metrological characteristics affecting the results and
measurement errors and intended for evaluation
technical level and quality of the ME, determining the result
and estimates of instrumental measurement error.
Section 1 Metrology Lecture 2 Metrology is the science of measurement
Groups of metrological characteristics:1) determining the scope of the ME:
● measuring range;
● sensitivity threshold.
2) determining the accuracy of measurements:
● error;
● convergence (closeness of results of repeated measurements in
the same conditions)
● reproducibility (repeatability of measurement results
the same size in different places, at different times,
different methods, different operators, but in
similar conditions).
Accuracy class - a generalized metrological characteristic,
determined by the limits of permissible errors, as well as
other characteristics that affect accuracy.
Designation of accuracy classes:
K = |γmax |
a) 1.0;
K = |δmax |
a) 1, 0; b) 1.0/0.5
b) 1.0
Section 1 Metrology Lecture 2 Metrology is the science of measurement
2.5 State system of industrial devices and meansAutomation (GSP)
The purpose of the GSP is the creation of scientifically based series of instruments and
devices with unified characteristics and
constructive performance.
Main groups of SHG funds:
● means for obtaining measurement information;
● means for receiving, converting and transmitting information;
● means for converting, processing and storing information and
formation of management teams.
System-technical principles of GSP:
● minimization of the nomenclature and quantity;
● block-modular construction;
● aggregation (construction of complex devices and systems from
unified units, blocks and modules or standard designs
conjugation method);
● compatibility (energy, functional, metrological,
constructive, operational, informational).
10. Metrology, standardization and certification in the electric power industry
METROLOGYSTANDARDIZATION
QUALITY
Lecture 3 Processing measurement results
CERTIFICATION
1. Measurements in the quality assessment system
products.
2. Calculation of the value of the measured quantity.
3. The procedure for estimating the error.
4. Estimating the error of single measurements.
5. Estimation of test error.
6. Evaluation of quality control errors.
11. Section 1 Metrology Lecture 3 Processing of measurement results
3.1 Measurements in the product quality assessment systemEvaluation of product quality in the determination or control of quantitative
and quality characteristics of products through
measurements, analysis, tests.
The purpose of measuring characteristics is to find the value of the corresponding
physical quantity.
The purpose of measuring control is to conclude on the suitability of products and
compliance with regulations.
Measurement steps:
● selection and use of an appropriate certified methodology
measurements (DSTU 3921.1-99);
● selection and training of trusted ME;
● performance of measurements (single; multiple;
statistical);
● processing and analysis of measurement results;
● decision-making on product quality (product certification).
12. Section 1 Metrology Lecture 3 Processing of measurement results
3.2 Calculation of measured valueLet the model of the object (of the measured value)
Х = ƒ (X1, X2, …, Xm) – ∆met;
during measurements, the results of observations Xij,
i = 1, …, m is the number of directly measured input values;
j = 1, …, n is the number of observations for each input value.
Measurement result:
~
X:
~
X X p
Order of finding
1) elimination of known systematic errors by introducing
corrections ∆c ij:
X΄ij \u003d Xij - ∆c ij;
2) calculation of the arithmetic mean of each input value:
n
Xij
~
X j 1 ;
i
n
13. Section 1 Metrology Lecture 3 Processing of measurement results
3) calculation of RMS estimates of the results of observations of each quantity:n
~ 2
(X ij X i)
S(Xi)
j1
(n 1)
4) assessment of the accuracy of measurements (exclusion of gross errors)
- according to the Smirnov criterion
(comparing the values
Vij
~
X ij X i
S(Xi)
with Smirnov coefficients)
- according to Wright's criterion;
5) refinement of the arithmetic mean of each input value and
calculation of the measured value:
~
~
~
X f X 1 ... X m Δmet.
14. Section 1 Metrology Lecture 3 Processing of measurement results
3.3 Error estimation procedure1) calculation of RMS estimates
– input values:
n
~
S(Xi)
~ 2
(X ij X i)
j1
n(n1)
– measurement result:
S(X)
m
f
~
S(X)
i
X
1
i
2
2) determination of the confidence limits of the random component
errors:
Δ P t P (v) S (X) ,
tP(v) is the quantile of Student's distribution for a given Рd
with the number of degrees of freedom v = n – 1.
15. Section 1 Metrology Lecture 3 Processing of measurement results
3) calculation of bounds and standard deviation of the non-excluded systematicerror component:
Δ ns k
f
Δnsi
X
1
i
m
2
Sns
;
Δns
3k
k = 1.1 at Pd = 0.95;
∆nsi is determined from available information;
4) calculation of the RMS of the total error:
5) evaluation of measurement error
if ∆ns /
S(X)< 0,8
if ∆ns /
S(X) > 8
if 0.8 ≤ ∆ns /
S(X) ≤ 8
S
2
S (X) 2 Sns
;
∆P = ∆P;
∆P = ∆ns;
∆P
Δ R Δ ns
S
S (X) Sns
16. Section 1 Metrology Lecture 3 Processing of measurement results
3.4 Estimating the error of single measurementsdirect measurements (i = 1,
j = 1)
~
X X
R
~
X \u003d Hism - ∆c; ∆Р = ∆max,
(∆max through instrument accuracy class).
indirect measurements (i = 2, …, m,
j = 1)
~
X X
~
~
~
X f X 1 ... X m met.
R
∆P
2
f
∆ max i ;
X
1
i
m
17. Section 1 Metrology Lecture 3 Processing of measurement results
● ifX = ∑Xi
X
● if
∆P
X1 ... X
X 1 ... X m
m
2
Δ
1
max i
m
δX
● if
X = kY
∆Х = k ∆Ymax
● if
X=Yn
δХ = n δYmax
(∆max and
δmax
2
δ max i
1
∆P
∆Х = nYn-1∆Y max
are calculated through the accuracy class).
δX X
100%
18. Section 1 Metrology Lecture 3 Processing of measurement results
3.5 Evaluation of test uncertaintyX
Let X = f(Y).
ism
∆set - the error of setting the Y value
ism
Test error X
Spanish ism
When X =
X
y
Y
ass
ƒ (X1, X2, …, Xm) maximum test error
Spanish ism
m
X
X i
i
i 1
2
ass
Y
19. Section 1 Metrology Lecture 3 Processing of measurement results
3.6 Evaluation of quality control errorsQuality Control Errors:
● type I control error: good product
identified as invalid.
● type II control error: unsuitable products
identified as valid.
Statistics:
Let X be controlled.
B - the number of units of products incorrectly accepted as suitable (in% of
total number measured);
G - the number of units of products, incorrectly rejected.
S
As
100%
X
AS
B
G
1,6
3
5
0,37…0,39
0,87…0,9
1,6…1,7
0,7…0,75
1,2…1,3
2,0…2,25
20. Metrology, standardization and certification in the electric power industry
METROLOGYSTANDARDIZATION
QUALITY
Lecture 4 Quality of electrical energy
CERTIFICATION
1. Electrical quality
energy and work of consumers.
2. Power quality indicators.
3. Determination of power quality indicators.
21. Section 1 Metrology Lecture 4 Electric power quality
4.1 Electricity quality and consumer performanceElectromagnetic environment Power supply system and connected to
her electrical apparatus and equipment connected conductively and
interfere with each other's work.
Electromagnetic compatibility of technical means
normal operation in the existing electromagnetic environment.
Permissible levels of interference in the electrical network characterize the quality
electricity and are called power quality indicators.
Electric power quality degree of conformity of its parameters
established standards.
Indicators of the quality of electrical energy, methods for their assessment and norms
GOST 13109-97: “Electric energy. Compatibility of technical
means electromagnetic. Electricity quality standards in
general purpose power supply systems.
22. Section 1 Metrology Lecture 4 Electric power quality
Properties of electrical energyVoltage deviation Actual voltage difference in
steady state operation of the power supply system from its
nominal value with a slow load change.
Voltage fluctuations fast-changing voltage deviations
lasting from half a cycle to several seconds.
Voltage unbalance Three-phase voltage unbalance
Non-sinusoidal voltage distortion of the sinusoidal form.
voltage curve.
Frequency deviation deviation of the actual AC frequency
voltage from the nominal value in steady state
operation of the power supply system.
Voltage dip A sudden and significant drop in voltage (<
90% Un) lasting from several periods to several
dozens
seconds followed by voltage recovery.
Temporary overvoltage sudden and significant increase
voltage (> 110% Un) for more than 10 milliseconds.
Surge voltage sudden increase in voltage
less than 10 milliseconds long.
23. Section 1 Metrology Lecture 4 Electric power quality
Properties of electrical energy and probable culprits for its deteriorationProperties of electricity
The most likely culprits
Voltage deviation
Energy supply organization
Voltage fluctuations
Consumer with variable load
Non-sinusoidal voltage Consumer with non-linear load
Voltage unbalance
Consumer with asymmetric
load
Frequency deviation
Energy supply organization
voltage dip
Energy supply organization
voltage pulse
Energy supply organization
Temporary overvoltage
Energy supply organization
24. Section 1 Metrology Lecture 4 Electric power quality
Email Properties energy
Voltage deviation Technological settings:
service life, probability of accident
technological process duration and
cost price
Electric drive:
reactive power (3…7% per 1%U)
torque (25% at 0.85Un), current consumption
life time
Lighting:
lamp life (4 times at 1.1 Un)
luminous flux (for 40% of incandescent lamps and
for 15% fluorescent lamps at 0.9 Un),
LL flicker or do not light up when< 0,9 Uн
25. Section 1 Metrology Lecture 4 Electric power quality
The influence of the properties of electricity on the work of consumersEmail Properties energy
Voltage fluctuations
Impact on the work of consumers
Technological installations and electric drive:
service life, performance
product defects
potential for equipment damage
vibrations of electric motors, mechanisms
shutdown of automatic control systems
shutdown of starters and relays
Lighting:
light pulse,
labor productivity,
workers' health
26. Section 1 Metrology Lecture 4 Quality of electrical energy
The influence of the properties of electricity on the work of consumersEmail Properties energy
Impact on the work of consumers
Voltage unbalance
Electrical equipment:
network losses,
braking torques in electric motors,
service life (twice at 4% reverse
sequences), work efficiency
phase imbalance and consequences, as with a deviation
voltage
Non-sinusoidality
voltage
Electrical equipment:
single-phase short circuits to earth
cable transmission lines, breakdown
capacitors, line losses, line losses
electric motors and transformers,
Power factor
Frequency deviation
collapse of the power system
emergency situation
27. Section 1 Metrology Lecture 4 Electric power quality
4.2 Power quality indicatorsEmail Properties energy
Level of quality
Voltage deviation
Steady voltage deviation δUу
Voltage fluctuations
Span of voltage change δUt
Flicker dose Pt
Non-sinusoidality
voltage
Sinusoidal distortion factor
voltage curve KU
Coefficient of the nth harmonic
voltage component KUn
Asymmetry
stresses
reverse sequence K2U
Voltage unbalance factor according to
zero sequence K0U
28. Section 1 Metrology Lecture 4 Electric power quality
Email Properties energyLevel of quality
Frequency deviation
Frequency deviation Δf
voltage dip
Voltage dip duration ΔUп
Voltage dip depth δUп
voltage pulse
Impulse voltage Uimp
Temporary
surge
Temporary overvoltage coefficient KperU
Duration of temporary overvoltage ΔtperU
29. Section 1 Metrology Lecture 4 Electric power quality
4.3 Determination of power quality indicatorsSteady voltage deviation δUу:
u u
Uy
U at U nom
U nom
100%
n
2
U
i n
– root mean square value of voltage
1
Ui values are obtained by averaging at least 18 measurements over the interval
time 60 s.
Normally permissible δUу = ±5%, limiting ±10%.
30. Section 1 Metrology Lecture 4 Electric power quality
The range of voltage change δUt:U
U i U i 1
U t
100%
U nom
Ui
Ui+1
t
t
Ui and Ui+1 are the values of successive extrema U,
whose root mean square value has the shape of a meander.
The maximum allowable range of voltage changes are given in
standard in the form of a graph
(of which, for example, δUt = ±1.6% at Δt = 3 min, δUt = ±0.4% at Δt = 3 s).
31. Section 1 Metrology Lecture 4 Quality of electrical energy
The distortion factor of the sinusoidal voltage curve KU:m
KU
2
U
n
n 2
U nom
100%
Un is the effective value of the n-harmonic (m = 40);
Normally permissible KU,%
Maximum permissible KU,%
at Un, kV
at Un, kV
0,38
6 – 20
35
0,38
6 – 20
35
8,0
5
4,0
12
8,0
6,0
KU is found by averaging the results of n ≥ 9 measurements over 3 s.
32. Section 1 Metrology Lecture 4 Electric power quality
The coefficient of the n-th harmonic component of the voltage КUnKUn
Ut
100%
U nom
Normally admissible КUn:
Odd harmonics, not multiples of 3 Maximum permissible KU at Un
at Un, kV
n
0,38
6 – 20
35
n
0,38
6 – 20
35
5
6,0%
4,0%
3,0%
3
2,5%
1,5%
1,5%
7
5,0%
3,0%
2,5%
9
0,75%
0,5%
0,5%
11
3,5%
2,0%
2,0%
Maximum allowable КUn = 1.5 КUn norms
KUn is found by averaging the results of n ≥ 9 measurements over 3 s.
33. Section 1 Metrology Lecture 4 Quality of electrical energy
Coefficient of voltage unbalance on the reverseK2U sequences
K 2U
U2
100%
U1
U1 and U2 are positive and negative sequence voltages.
Normally permissible K2U = 2.0%, maximum permissible K2U = 4.0%
Voltage asymmetry coefficient at zero
K0U sequences
K0U
3U0
100%
U1
U0 - zero sequence voltage
Normally permissible K0U = 2.0%, maximum permissible K0U = 4.0% at
U = 380 V
34. Section 1 Metrology Lecture 4 Electric power quality
Voltage dip duration ΔUпMaximum allowable value ΔUp = 30 s at U ≤ 20 kV.
Voltage dip depth
U p
U nom U min
100%
U nom
Temporary overvoltage factor
KperU
U m max
2U nom
Um max - the largest amplitude value during the control.
Frequency deviation
Δf = fcp – fnom
fcp is the average of n ≥ 15 measurements over 20 s.
Normally permissible Δf = ±0.2 Hz, maximum permissible ±0.4 Hz.
35. Metrology, standardization and certification in the electric power industry
METROLOGYSTANDARDIZATION
QUALITY
Lecture 5 Ensuring unity and
required measurement accuracy
1.
2.
3.
4.
CERTIFICATION
Unity of measurements and its maintenance.
Reproduction and transmission of units of physical quantities.
SIT verification.
SIT calibration.
36. Section 1 Metrology Lecture 5 Ensuring the unity and necessary accuracy of measurements
5.1 Unity of measurements and its provisionThe main task of the organization of measurements is the achievement of comparable
measurement results of the same objects performed in
different times, in different places, with the help of different methods and means.
Uniformity of measurements measurements are carried out according to standard or
certified methods, the results are expressed in legal
units, and the errors are known with a given probability.
Cause
Consequence
Using the Wrong Techniques
measurements, wrong choice
SIT
Violation of technological
processes, loss of energy
resources, emergencies, marriage
products, etc.
Misconception
measurement results
Non-recognition of measurement results
and product certification.
37. Section 1 Metrology Lecture 5 Ensuring the uniformity and necessary accuracy of measurements
Ensuring the uniformity of measurements:● metrological support;
● legal support.
Metrological support establishment and application of scientific and
organizational bases, technical means, rules and norms for
achieving unity and the required accuracy of measurements
(regulated by DSTU 3921.1-99).
Components of metrological support:
● scientific basis
metrology;
● technical basis
system of state standards,
unit size transfer system,
working SIT, system of standard
samples of the composition and properties of materials;
● organizational basis metrological service (network
institutions and organizations);
● regulatory framework
laws of Ukraine, DSTU, etc.
regulations.
38. Section 1 Metrology Lecture 5 Ensuring the unity and necessary accuracy of measurements
Legal support of the law of Ukraine "On metrology andmetrological activity” and other regulatory legal acts.
Form of ensuring the uniformity of measurements state
metrological control and supervision (MMC and N)
The purpose of MMC and N is to verify compliance with the requirements of the law and regulations of Ukraine and regulatory documents of metrology.
MMC and N SIT facilities and measurement methods.
Types of MMC and N:
Mining and Metallurgical Complex ● State testing of ME and approval of their types;
● State metrological certification of MI;
● verification of ME;
● accreditation for the right to carry out metrological works.
HMN ● Supervision of ensuring the uniformity of measurements Verification:
– state and application of ME,
– application of certified measurement methods,
– the correctness of the measurements,
– compliance with the requirements of the law, metrological norms and rules.
39. Section 1 Metrology Lecture 5 Ensuring the unity and necessary accuracy of measurements
5.2 Reproduction and transmission of units of physical quantitiesReproduction of a unit is a set of activities for
materialization of a unit of physical
values with the highest precision.
Etalon is a means of measuring technology that provides
reproduction, storage and transmission of unit size
physical quantity.
References:
international
state
secondary
State standard is an officially approved standard,
unit reproduction
measurements and transfer of its size to secondary
standards with the highest accuracy in the country.
40. Section 1 Metrology Lecture 5 Ensuring the unity and necessary accuracy of measurements
Secondary standards:● reference copy;
● working standard.
Working standard for verification or calibration of ME.
Unit size transfer:
● direct comparison method;
● comparison method using a comparator.
Unit Size Transfer Scheme:
state standard
↓
standard - copy
↓
working standards
↓
exemplary SIT
↓
working SIT
At each stage of the transfer of the unit, the loss of accuracy is 3 to 10 times.
41. Section 1 Metrology Lecture 5 Ensuring the unity and necessary accuracy of measurements
The unity and accuracy of measurement are determined by the reference base of the country.National standard base of Ukraine 37 state standards.
State standards of units of electrical quantities:
● standard unit of electric current strength
(S ≤ 4∙10-6, δс ≤ 8∙10-6 for direct current,
S ≤ 10-4, δс ≤ 2∙10-4 for alternating current);
● standard voltage unit
(S ≤ 5∙10-9, δс ≤ 10-8 for EMF and DC voltage,
S ≤ 5∙10-5, δс ≤ 5∙10-4 for AC voltage);
● standard unit of electrical resistance
(S ≤ 5∙10-8, δс ≤ 3∙10-7);
● time and frequency reference
(S ≤ 5∙10-14, δс ≤ 10-13);
42. Section 1 Metrology Lecture 5 Ensuring the unity and necessary accuracy of measurements
5.3 Verification of MEVerification of the ME, determination of the suitability of the ME for use on the basis of
results of control of their metrological characteristics.
The purpose of verification is the determination of errors and other metrological
characteristics of the ME, regulated by TS.
Verification types:
● primary (at release, after repair, at import);
● periodic (during operation)
● extraordinary (if the verification mark is damaged,
loss of certificate of verification, commissioning
after long term storage)
● inspection (during the implementation of the state
metrological control)
● expert (in case of disputes
regarding metrological characteristics, suitability
and correct use of SIT)
43. Section 1 Metrology Lecture 5 Ensuring the unity and necessary accuracy of measurements
All ME, which are in operation and for whichsubject to state metrological supervision.
Verification is also subject to working standards, exemplary measuring instruments and those means
which are used during state tests and
state certification of SIT.
Verification is made:
● territorial bodies of the State Standard of Ukraine accredited for
the right to conduct it;
● accredited metrological services of enterprises and organizations.
Verification results are documented.
5.3 Calibration of the MEMS
Calibration of the SIT determination under appropriate conditions or
control of metrological characteristics of ME, on
which are not covered by the state
metrological supervision.
44. Section 1 Metrology Lecture 5 Ensuring the unity and necessary accuracy of measurements
Calibration types:● metrological (performed by the metrological
laboratory);
● technical (performed by the experimenter).
Metrological calibration functions:
● determination of actual values of metrological
characteristics of the SIT;
● determination and confirmation of the suitability of the ME for use.
Technical calibration function:
● determination of the actual values of individual characteristics
SIT immediately before using it in measurements.
The need for calibration in the operation of ME, which are not
extends state metrological supervision,
defined by their user.
Metrological calibration is carried out by accredited laboratories.
Technical calibration is carried out by the user of the ME.
45. Metrology, standardization and certification in the electric power industry
METROLOGYSTANDARDIZATION
QUALITY
Lecture 6 Basics of expert qualimetry
CERTIFICATION
1. Evaluation of product quality.
2. Expert methods for determining
quality indicators.
3. Methods for obtaining expert assessments.
4. Processing of expert assessment data.
46. Section 1 Metrology Lecture 6 Fundamentals of expert qualimetry
6.1 Evaluation of product qualityQualimetry evaluation of product quality.
Product quality is a multidimensional product property, generalized
characteristics of its consumer properties;
non-physical quantity, estimated
quality indicators.
Quality assessment versus quality indicators versus indicators
exemplary products.
Level of quality:
● physical quantity (measured by measuring methods);
● non-physical quantity (estimated by expert methods).
Quality indicators:
● single;
● complex (formed from single ones).
47. Section 1 Metrology Lecture 6 Fundamentals of expert qualimetry
Comprehensive indicators:● single-level;
● multilevel;
● generalized.
Formation of complex indicators:
● according to known functional dependence;
● according to the dependence accepted by agreement;
● according to the weighted average principle:
n
- arithmetic weighted average:
Q ciQi
;
i 1
n
– weighted geometric mean:
Q
n
Cі - weight coefficients: usually
c
i 1
i
ci
Q
i
i 1
n
c
i
i 1
1
.
.
48. Section 1 Metrology Lecture 6 Fundamentals of expert qualimetry
6.2 Expert methods for determining quality indicatorsExpert methods when measurements are not possible or
economically unjustified.
Expert
methods
Organoleptic
method
Sociological
method
Organoleptic method for determining the properties of an object using
human sense organs
(sight, hearing, touch, smell, taste).
The sociological method of determining the properties of an object based on
mass surveys of the population or its groups
(each individual acts as an expert).
49. Section 1 Metrology Lecture 6 Fundamentals of expert qualimetry
Expert assessment is the result of a rough assessment.To increase the reliability of the assessment, the group method of assessment
(expert committee).
Formation of an expert commission through testing
(competency test).
The necessary conditions:
● consistency of expert assessments;
● independence of experts' assessments.
The size of the expert group is ≥ 7 and ≤ 20 people.
Checking Consistency of Estimates
when forming an expert group:
● according to the consistency of assessments
(Smirnov criterion);
● according to the coefficient of concordance.
50. Section 1 Metrology Lecture 6 Fundamentals of expert qualimetry
1. Checking the consistency of expert estimates by the Smirnov criterion βArithmetic mean value of the score
m is the number of experts;
RMS estimates
S
~ 2
Q
Q
i)
m 1
.
An estimate is considered consistent if
~
Q
qi
~
QiQ
S
m
,
.
2. Checking the consistency of expert estimates on the coefficient of concordance
Concordance coefficient
W
12S
m 2 (n 3 n)
n is the number of evaluated factors (product properties).
Estimates are consistent if
(n 1)tW 2
χ2 – goodness-of-fit criterion (quantile of χ2-distribution)
51. Section 1 Metrology Lecture 6 Fundamentals of expert qualimetry
6.3 Methods of obtaining expert opinionsAssessment tasks:
● ranking of homogeneous objects by degree
the severity of a given quality indicator;
● quantitative assessment of quality indicators
in arbitrary units or weight coefficients.
Building a ranked series:
a) pairwise matching of all objects
(“more” - “less”, “better” - “worse”);
b) compiling a ranked series
(in descending or ascending comparison scores).
Quantitative expert assessment in fractions of a unit or points.
The main characteristic of the scoring scale is the number of gradations
(evaluation points).
5-, 10-, 25- and 100-point scales are used.
52. Section 1 Metrology Lecture 6 Fundamentals of expert qualimetry
An example of constructing a scoring scale.1) the maximum overall assessment of products in points Qmax is established;
2) each individual quality indicator is assigned a weight
coefficient ci ;
3) according to ci , based on Qmax, set the maximum score
each indicator Qi max = сi Qmax ;
4) discounts are set from the ideal estimate of the indicator when reducing
quality ki ;
5) a score is determined for each indicator Qi = ki сi Qmax ;
6) the overall assessment of products in points is determined
n
QΣ =
Q
i 1
i
;
7) based on the possible scores, determine the number of degrees
quality (categories, varieties).
53. Section 1 Metrology Lecture 6 Fundamentals of expert qualimetry
6.4 Handling peer review data1. Checking the homogeneity of the array of estimates by the total estimate of ranks:
R Rij
j 1 i 1
n
m
2
j = 1, 2, 3 … n – rank number;
I = 1, 2, 3 … m – number of the expert;
Rij - ranks assigned by each expert.
An array is considered homogeneous if RΣ ≥ Rcr
(critical assessment Rcr according to the table for Rd = 0.95).
If the condition is not met, reevaluate or
formation of a new group of experts.
2. Building a ranked series
m
Rj
m
Ri1; ........ Rin
i 1
i 1
54. Section 1 Metrology Lecture 6 Fundamentals of expert qualimetry
Estimation table Rkr for confidence probability Рd = 0.95Number of experts
Number of ranks
3
4
5
6
7
8
9
2
6,6
1,2
2,2
3,6
5,0
7,1
9,7
3
12,6
2,6
4,7
7,6
11,1
15,8
21,6
4
21,7
4,5
8,1
13,3
19,7
28,1
38,4
5
33,1
6,9
12,4
20,8
30,8
43,8
60,0
6
47,0
9,8
17,6
30,0
44,4
63,1
86,5
7
63,0
13,1
23,8
40,7
60,5
85,0
115,0
8
81,7
17,0
29,8
48,3
73,2
105,0
145,0
9
102,6
21,4
37,5
60,9
92,8
135,0
185,0
10
126,1
26,3
46,2
75,0
113,8
160,0
225,0
M (multiplier)
10
100
100
100
100
100
100
Rcr = k (m, n) M.
55. Metrology, standardization and certification in the electric power industry
METROLOGYSTANDARDIZATION
QUALITY
Lecture 7 Metrological Service
CERTIFICATION
1. State metrological
Ukrainian system.
2. Metrological service of Ukraine.
3. International and regional metrology organizations.
56. Section 1 Metrology Lecture 7 Metrological service
7.1 State metrological system of UkraineState metrological system of Ukraine:
● legal framework;
● metrological service.
● implementation of a unified technical policy in the field of metrology
● protection of citizens and the national economy from the consequences
unreliable measurement results
● saving all kinds of material resources
Functions ● raising the level of fundamental research and scientific
GMSU
developments
● ensuring the quality and competitiveness of domestic
products
● creation of scientific, technical, regulatory and organizational
bases for ensuring the uniformity of measurements in the state
57. Section 1 Metrology Lecture 7 Metrological Service
Legislative base of the metrological system of Ukraine● law of Ukraine "On metrology and metrological activity"
● state standards of Ukraine (DSTU);
● industry standards and specifications;
● standard regulation on metrological services of central authorities
executive power, enterprises and organizations.
● state metrological system
● application, reproduction and storage of units of measurement
● application of ME and use of measurement results
● structure and activities of state and departmental
Main
metrological services
provisions
● state and departmental metrological
law
control and supervision
● organization of state tests, metrological
certification and verification of measuring equipment
● financing of metrological activities
58. Section 1 Metrology Lecture 7 Metrological Service
Normative documents on metrology● Development and approval of normative documents on metrology
carried out in accordance with the law.
Gospotrebstandart of Ukraine are binding
central and local executive authorities, bodies
local self-government, enterprises, organizations, citizens -
business entities and foreign
manufacturers.
● Requirements of normative documents on metrology, approved
central executive authorities are mandatory
for execution by enterprises and organizations related to the field
management of these bodies.
● Enterprises and organizations can develop and approve in
in their field of activity documents on metrology, which
specify the regulatory standards approved by the State Consumer Standards of Ukraine
documents and do not contradict them.
Law of Ukraine "On metrology and metrological activity"
59. Section 1 Metrology Lecture 7 Metrological service
7.2 Metrological Service of UkraineMetrological service of Ukraine:
● state metrological service;
● departmental metrological service.
The State Metrological Service organizes, implements and
coordinates activities to ensure the uniformity of measurements.
● State Committee for Technical Regulation and
consumer policy (Gospotrebstandart of Ukraine)
● state scientific metrological centers
● territorial metrological bodies of Gospotrebstandart
Structure ● Public service of common time and reference
HMS
frequencies
● State Service for Reference Materials of Substances and
materials
● Public service standard reference data on
physical constants and properties of substances and materials
60. Section 1 Metrology Lecture 7 Metrological service
Main functions of HMS:● development of scientific, technical, legislative and organizational
basics of metrological support
● development, improvement and maintenance of the reference base
● development of regulatory documents to ensure the uniformity of measurements
● standardization of norms and rules for metrological support
● creation of systems for transferring sizes of units of measurements
● development and certification of measurement procedures
● organization of state verification and calibration of ME
● state metrological control and supervision of production and
the use of ME, compliance with metrological norms and rules
● ensuring the unity of time and frequency measurements and determining
Earth rotation parameters
● development and implementation of standard samples of composition and properties
substances and materials
● development and implementation of standard reference data on physical
constants and properties of substances and materials
61. Section 1 Metrology Lecture 7 Metrological service
Departmental metrological service:● central executive authorities (ministries, departments);
● business associations;
● enterprises and organizations;
● ensuring the uniformity of measurements in the field of their activities
● development and implementation of modern measurement methods,
SIT, standard samples of the composition and properties of substances and
materials
Main
functions
Navy
● organization and implementation of departmental
metrological control and supervision
● development and certification of measurement methods,
metrological certification, verification and calibration of measuring instruments
● organization and conduct of state tests,
departmental verification, calibration and repair of ME
● organization of metrological support for tests and
product certification
● carrying out accreditation of measuring and calibration
laboratories
62. Section 1 Metrology Lecture 7 Metrological service
● Metrological services of enterprises and organizations are created withthe purpose of organizing and performing work on metrological support
development, production, testing, use of products.
● The metrological service of the enterprise and organization includes
metrological division and (or) other divisions.
● Works to ensure the uniformity of measurements are among the main
types of work, and subdivisions of the metrological service - to the main
production departments.
Model regulation on metrological services of central
executive authorities, enterprises and organizations
For the right to conduct:
● state tests,
● verification and calibration of ME,
● certification of measurement methods,
● responsible measurements
accreditation
63. Section 1 Metrology Lecture 7 Metrological service
7.3 International and regional metrology organizationsMain international metrological organizations:
● International Organization of Weights and Measures;
● International Organization of Legal Metrology;
● International Electrotechnical Commission.
International Organization of Weights and Measures (OIPM)
(created on the basis of the Metric Convention of 1875, 48 participating countries).
Supreme body: General Conference on Weights and Measures.
Governing Body: International Committee for Weights and Measures (CIPM):
Composition: 18 largest physicists and metrologists of the world;
Structure: 8 Advisory Committees:
- on electricity,
– thermometry,
- definition of the meter,
- the definition of a second,
- by units of physical quantities, etc.
64. Section 1 Metrology Lecture 7 Metrological Service
At CIPM International Bureau of Weights and Measures (BIPM)Main tasks of BIPM:
● preservation of international standards of units and comparison with them
national standards;
● improvement of the metric system of measurements;
● coordination of activities of national metrological
organizations.
International Organization of Legal Metrology (OIML)
(since 1956, more than 80 participating countries).
Supreme body: International Legislative Conference
metrology.
Leading body: International Legislative Committee
metrology (ICML).
Under ICML International Bureau of Legal Metrology.
65. Section 1 Metrology Lecture 7 Metrological service
OIML Goals:● establishing the uniformity of measurements at the international level;
● ensuring the convergence of measurement and research results in
different countries to achieve the same product characteristics;
● development of recommendations for assessing measurement uncertainties,
theory of measurements, methods of measurement and verification of ME, etc.;
● SIT certification.
International Electrotechnical Commission (IEC)
(since 1906, 80 participating countries) main international body
on standardization in the field of electrical engineering, radio electronics and communications
and certification of electronic products.
Main regional organizations
COOMET -
metrological organization of the countries of central and eastern
Europe (including Ukraine);
EUROMET is the metrological organization of the EU;
VELMET - European Association for Legal Metrology;
EAL-
european sizing association. MINISTRY OF EDUCATION OF THE NIZHNY NOVGOROD REGION
GBPOU "URENSK INDUSTRIAL AND ENERGY COLLEGE"
Agreed:at the methodological council
T.I. Solovieva
"____" ______________ 201 g
I approve:
Deputy Director for SD
T.A. Maralova
"____" ______________ 201 g
Work program of the discipline
OP.03. Metrology, standardization, certification
by specialty 13.02.07 Power supply (by industry)
Uren
Work program of the academic discipline OP.03. Metrology, standardization, certification was developed on the basis of the Federal State Educational Standard (hereinafter referred to as FSES) in the specialty of secondary vocational education (hereinafter referred to as SVE) 13.02.07 Energy supply (by industry) of an enlarged group of specialties 13.00.00 Electric and thermal power engineering.
Organization-developer: GBPOU "Urensk industrial and energy technical school"
Developers: Ledneva Marina Mikhailovna,
special teacher disciplines,
GBPOU "Urensk industrial and energy technical school".
Considered:
MO of pedagogical workers
special disciplines
№ 1 fromAugust 28 2017
Head of the Ministry of Defense _________
CONTENT
1. PASSPORT OF THE PROGRAM OF THE EDUCATIONAL DISCIPLINE
OP .03. Metrology, standardization, certification
1.1 Scope of the example program
The work program of the discipline is part of the main professional educational program in accordance with the Federal State Educational Standard in the specialty SPO 13.02.07 Energy supply (by industry) of an enlarged group of specialties 13.00.00 Electric and thermal power engineering.
1.2 The place of the academic discipline in the structure of the main professional educational program: academic discipline OP.03. Metrology, standardization, certificationincluded in the professional cycle,is angeneral professionaloh disciplines oh.
1.3 Goals and objectives of the academic discipline - requirements for the results of mastering the discipline:
The result of mastering the academic discipline is the mastery of the type of professional activity by students, including the formation of professional (PC) and general (OK) competencies: OK 1-9, PC 1.1 - 1.5, 2.1 - 2.6, 3.1 - 3.2.
OK1. Understand the essence and social significance of your future profession, show a steady interest in it.
OK2. Organize their own activities, choose typical methods and methods for performing professional tasks, evaluate their effectiveness and quality.
OK 3. Make decisions in standard and non-standard situations and be responsible for them.
OK 4. Search and use the information necessary for the effective implementation of professional tasks, professional and personal development.
OK 5. Use information and communication technologies in professional activities.
OK 6. Work in a team and team, communicate effectively with colleagues, management, consumers.
OK 7. Take responsibility for the work of team members (subordinates), the result of completing tasks.
OK 8. Independently determine the tasks of professional and personal development, engage in self-education, consciously plan advanced training.
OK 9. Navigate in conditions of frequent change of technologies in professional activity.
PC 1.2. Perform the main types of maintenance of transformers and converters of electrical energy.
PC 1.3. Perform the main types of work on maintenance of switchgear equipment of electrical installations, relay protection systems and automated systems.
PC 1.4. Perform basic maintenance work on overhead and cable power lines.
PC 1.5. Develop and execute technological and reporting documentation.
PC 2.2. Find and repair equipment damage.
PC 2.3. Carry out electrical repairs.
PC 2.4. Estimate the cost of repairing power supply devices.
PC 2.5. Check and analyze the condition of devices and instruments used in the repair and adjustment of equipment.
PC 2.6. Perform adjustment and adjustment of devices and instruments for the repair of equipment of electrical installations and networks.
PC 2.1. Plan and organize equipment maintenance work.
PC 3.1. Ensure the safe production of scheduled and emergency work in electrical installations and networks.
PC 3.2. Prepare documentation on labor protection and electrical safety during the operation and repair of electrical installations and networks.
be able to:
apply the requirements of regulatory documents to the main types of products (services) and processes;
As a result of mastering the academic discipline, the student mustknow :
quality assurance forms
the maximum study load of a student is 96 hours, including:
obligatory classroom teaching load of the student 64 hours;
independent work of the student 32 hours.
2. STRUCTURE AND CONTENT OF THE EDUCATIONAL DISCIPLINE
2.1 The scope of the academic discipline and types of educational work
laboratory workspractical work
Independent work of the student (total)
32
including:
extracurricular work
individual tasks
final examination in the shape ofexam
Thematic plan and the content of the academic discipline OP.03. Metrology, standardization and certification
Name of sections and topicsThe content of the educational material, laboratory and practical work, independent work of students, term papers (project)
Watch volume
Learned competencies
Level of development
1
2
3
4
5
Section 1. Metrology
44
Topic 1.1
Fundamentals of the theory of measurements
6
Main characteristics of measurements. The concept of a physical quantity. The value of physical units. Physical quantities and measurements. Standards and exemplary measuring instruments.
OK 1-9
PC 1.1-1.5
PC 2.1-2.6
PC 3.1-3.2
Topic 1.2
Measuring instruments
16
Measuring instruments and their characteristics. Classification of measuring instruments.
OK 1-9
PC 1.1-1.5
PC 2.1-2.6
PC 3.1-3.2
Metrological characteristics of measuring instruments and their regulation. Metrological support and its fundamentals.
Independent work
Write a summary of the compilation of a block of measures of the required size.
Theme 1.3Metrological assurance of measurements
22
The choice of measuring instruments. Methods for determining and accounting for errors. Processing and presentation of measurement results.
OK 1-9
PC 1.1-1.5
PC 2.1-2.6
PC 3.1-3.2
Lab No. 1 : Identification of measurement errors.
Lab #2: The device and application of measuring instruments for special purposes.
Lab #3: Measuring the dimensions of parts using gauge blocks.
Lab #4: Measuring the parameters of parts with the help of rods - tools.
Lab No. 5 : Measurement of the parameters of parts using a micrometer.
Lab #6: Setting up instruments for measuring electrical quantities.
Independent work
Write a summary describing the parameters for culling parts.
Demos:
A computer.
Projector.
Devices:
Caliper ШЦ-I-150-0.05.
Smooth micrometer MK25.
Lever micrometer MP25.
KMD set No. 2 class 2 .
Posters:
Classification of measuring instruments
Metrological characteristics of measuring instruments:
a) Transformation function.
b) The mechanism of formation of the main and additional errors of SI.
c) Dependence of MI error on the level of the input signal.
d) Basic error and accuracy classes of SI according to GOST 8.401-80.
Posters: Measurement uncertainties
1. Normal distribution of random errors.
2. Interval estimation of random error.
3. Normal distribution law in the presence of a systematic error.
4. Determination of the confidence interval by the integral distribution function of the error.
5. Systematization of errors.
Section 2. Basics of standardization
30
Topic 2.1 State standardization system
14
Normative documents on standardization, their categories. Types of standards. All-Russian classifiers. Requirements and procedure for the development of standards.
OK 1-9
PC 1.1-1.5
PC 2.1-2.6
PC 3.1-3.2
Lab #7: Studying the construction of the standard.
Lab #8: Building a list of objects and subjects of standardization.
Independent work
Draw a scheme for constructing parametric series.
Topic 2.2Product quality indicators
16
1 .
Classification of accommodation facilities. Standardization methods.
OK 1-9
PC 1.1-1.5
PC 2.1-2.6
PC 3.1-3.2
Methods for determining quality indicators. Fundamental state standards.
Lab #9: Determination of the quality of power supply products.
Independent work
write an essay on the topic "The quality of electrical materials and products."
Demos:
A computer.
Projector.
Posters:
The main provisions of the state standardization system (SSS).
Legal bases of standardization.
Organizational structure of the international organization for standardization ISO.
Determining the optimal level of unification and standardization.
Responsibility of the manufacturer, performer, seller for violation of consumer rights.
Block structure of the main provisions of the "Law on the Protection of Consumer Rights".
Section 3 Certification and Licensing Basics
22
Topic 3.1
General concepts of certification
6
Objects and purposes of certification. conditions for certification.
Topic 3.2 Certification system
Content of educational material
16
The concept of product quality. Protection of consumer rights. Certification Scheme.
Mandatory certification. Voluntary certification.
Lab #10: The procedure for filing claims for product quality.
Independent work
Write a summary - requirements for mandatory certification of products.
Demos:
A computer.
Projector.
Posters:
Total:
64
32
3. CONDITIONS FOR THE IMPLEMENTATION OF THE EDUCATIONAL DISCIPLINE
3.1 Minimum logistics requirements
The implementation of the program of the academic discipline requires the presence of a study room "Metrology, standardization and certification".
Study room equipment
seats by the number of students;
workplace of the teacher;
a set of educational and methodological documentation;
visual aids (GOST tables, textbooks and teaching aids).
Technical training aids
computer with licensed programs;
projector;
measuring tool (calipers, micrometers, calipers, gauges - of various sizes);
details of units and mechanisms suitable for measurements;
measuring instruments of electrical quantities.
3.2 Information support of training
Main sources:
1. Metrology, standardization and certification in the energy sector: textbook. allowance for students. Institutions Prof. Education / (S.A. Zaitsev, A.N. Tolstov, D.D. Gribanov, R. V. Merkulov). - M.: Publishing Center "Academy", 2014. - 224 p.
2. Collection of normative acts of the Russian Federation, - M .: EKMOS, 2006 (certified by the Ministry of Education and Science) (electronic version)
Additional sources:
Gribanov D.D. Fundamentals of metrology: textbook / D.D. Gribanov, S.A. Zaitsev, A.V. Mitrofanov. - M. : MSTU "MAMI", 1999.
Gribanov D.D. Fundamentals of certification: textbook. allowance / D.D. Gribanov - M .: MSTU "MAMI", 2000.
Gribanov D.D. Fundamentals of standardization and certification: textbook. allowance / D.D. Gribanov, S.A. Zaitsev, A.N. Tolstov. - M. : MSTU "MAMI", 2003.
Internet resources:
1. Ministry of Education of the Russian Federation. Access mode: http://www.ed.gov.ru
2. Federal portal "Russian education". Access mode: http://www.edu.ru
3. Russian search engine. Access mode: http://www.rambler.ru
4. Russian search engine. Access mode: http://www.yandex.ru
5. International search engine. Access mode: http://www.Google.ru
6. Electronic library. Access mode: http;//www.razym.ru
4. Monitoring and evaluation of the results of mastering the EDUCATIONAL Discipline
Monitoring and evaluation the results of mastering the academic discipline is carried out by the teacher in the process of conducting practical classes and laboratory work, testing, as well as the performance of individual tasks by students.
Learning Outcomes(learned skills, acquired knowledge)
Forms and methods of monitoring and evaluating learning outcomes
Skills:
use quality system documentation in professional activities;
draw up technological and technical documentation in accordance with the current regulatory framework;
bring non-systemic measurement values in line with current standards and the international system of units SI;
apply the requirements of regulatory documents to the main types of products (services) and processes.
Solving industrial situations during laboratory and practical classes.
Extracurricular independent work.
Knowledge:
tasks of standardization, its economic efficiency;
the main provisions of systems (complexes) of general technical and organizational and methodological standards;
basic concepts and definitions of metrology, standardization, certification and documentation of quality systems;
terminology and units of measurement in accordance with the current standards and the international system of units SI;
quality assurance forms.
Oral questioning, expert observation in practical classes, extracurricular independent work.
The assessment of individual educational achievements based on the results of current control is carried out in accordance with the universal scale (table).
The Constitution of the Russian Federation (Article 71) establishes that the standards, standards, the metric system and the calculation of time are under the jurisdiction of the Russian Federation. Thus, these provisions of the Constitution of the Russian Federation fix the centralized management of the main issues of legal metrology (units of quantities, standards and other metrological bases related to them). In these matters, the exclusive right belongs to the legislative bodies and state governing bodies of the Russian Federation. In 1993, the Law of the Russian Federation "On Ensuring the Uniformity of Measurements" was adopted, which defines:
- basic metrological concepts (uniformity of measurements, measuring instrument, standard of unit of measure, regulatory document for ensuring the uniformity of measurements, metrological service, metrological control and supervision, verification of measuring instruments, calibration of measuring instruments, and others);
- the competence of the State Standard of Russia in the field of ensuring the uniformity of measurements;
- the competence and structure of the State Metrological Service and other state services to ensure the uniformity of measurements;
- metrological services of state government bodies of the Russian Federation and legal entities (enterprises, organizations);
- basic provisions on units of quantities of the International System of Units, adopted by the General Conference on Weights and Measures;
- types and scope of metrological control and supervision;
- rights, duties and responsibilities of state inspectors to ensure the uniformity of measurements;
- obligatory creation of metrological services of legal entities using measuring instruments in the areas of distribution of state control and supervision;
- conditions for the use of measuring instruments in the areas of distribution of state control and supervision (type approval, verification);
- requirements for performing measurements according to certified methods;
- basic provisions of calibration and certification of measuring instruments;
- sources of funding for work to ensure the uniformity of measurements.
- analysis of the state of measurements at the enterprise;
- introduction of modern methods and measuring instruments, measurement techniques;
- introduction of methodological and regulatory documents in the field of metrological support of production;
- control of the performance of measuring instruments during their operation (in addition to verification);
- maintenance of MI in operation in accordance with the instructions of the operational documentation;
- current repair of measuring instruments; supervision over the condition and use of measuring instruments;
- accounting of measuring instruments at the enterprise.
- formation of the needs of the enterprise and its individual workshops in measuring instruments;
- formation of lists of measuring instruments subject to verification, including write-off;
- planning the verification of measuring instruments and fixing its results;
- planning of repairs of measuring instruments;
- calculations for verification and repair work;
- analysis of the work of maintenance personnel.
- hours of operation of the metering station;
- consumption and quantity of gas in working and normal conditions;
- average hourly and average daily gas temperature;
- average hourly and average daily gas pressure.
- align measuring instruments and their installation in accordance with the requirements of regulatory documents; pay attention to the insulation of the straight section of the pipeline where the thermometer is installed;
- equip metering units with measuring instruments for gas parameters (temperature, pressure);
- draw up technical documentation according to the attached form before the next verification date of 2002, but no later than the beginning of the heating season.
- It is necessary to develop a targeted program to ensure the unity of measurement, the introduction of GOST 51617-2000 and related activities.
- Conduct an inventory of measuring instruments at housing and communal services enterprises.
- Organize a metrological service.
- Provide presentation of graphs and lists.
- Verify all measuring instruments before the start of the heating season.
- Bring natural gas metering units in line with the requirements of current standards.
Metrology - the science of measurements, methods and means of ensuring their unity and ways to achieve the required accuracy.
Metrology is of great importance for progress in the field of design, production, natural and technical sciences, since increasing the accuracy of measurements is one of the most effective ways of understanding nature by man, discoveries and practical application of the achievements of exact sciences.
A significant increase in measurement accuracy has repeatedly been the main prerequisite for fundamental scientific discoveries.
Thus, the increase in the accuracy of measuring the density of water in 1932 led to the discovery of a heavy isotope of hydrogen - deuterium, which determined the rapid development of nuclear energy. Thanks to the ingenious comprehension of the results of experimental studies on the interference of light, carried out with high accuracy and refuting the previously existing opinion about the mutual motion of the source and receiver of light, A. Einstein created his world-famous theory of relativity. The founder of world metrology, D.I. Mendeleev, said that science begins where they begin to measure. Metrology is of great importance for all industries, for solving problems of increasing production efficiency and product quality.
Here are just a few examples that characterize the practical role of measurements for the country: the share of costs for measuring equipment is about 15% of all costs for equipment in mechanical engineering and approximately 25% in radio electronics; every day in the country a significant number of different measurements, numbering in the billions, are carried out, a significant number of specialists work in the profession related to measurements.
The modern development of design ideas and technologies of all branches of production testify to their organic connection with metrology. To ensure scientific and technological progress, metrology must be ahead of other areas of science and technology in its development, because for each of them, accurate measurements are one of the main ways to improve them.
Before considering various methods that ensure the uniformity of measurements, it is necessary to define the basic concepts and categories. Therefore, in metrology it is very important to use the terms correctly, it is necessary to determine what exactly is meant by this or that name.
The main tasks of metrology to ensure the uniformity of measurements and ways to achieve the required accuracy are directly related to the problems of interchangeability as one of the most important indicators of the quality of modern products. In most countries of the world, measures to ensure the uniformity and required accuracy of measurements are established by law, and in the Russian Federation in 1993 the law "On Ensuring the Uniformity of Measurements" was adopted.
Legal metrology sets the main task of developing a set of interrelated and interdependent general rules, requirements and norms, as well as other issues that need regulation and control by the state, aimed at ensuring the uniformity of measurements, progressive methods, methods and measuring instruments and their accuracy.
In the Russian Federation, the main requirements of legal metrology are summarized in the State Standards of the 8th class.
Modern metrology includes three components:
1. Legislative.
2. Fundamental.
3. Practical.
legal metrology- a section of metrology that includes sets of interrelated general rules, as well as other issues that need regulation and control by the state aimed at ensuring the uniformity of measurements and the uniformity of measuring instruments.
The issues of fundamental metrology (research metrology), the creation of systems of units of measurement, physical constant development of new measurement methods are engaged in theoretical metrology.
The issues of practical metrology in various fields of activity as a result of theoretical research are dealt with by applied metrology.
Metrology tasks:
Ensuring the uniformity of measurements
Definition of the main directions, development of metrological support of production.
Organization and conduct of condition analysis and measurements.
Development and implementation of metrological software programs.
Development and strengthening of the metrological service.
Metrology objects: Measuring instruments, standard, methods for performing measurements, both physical and non-physical (production quantities).
The history of the emergence and development of metrology.
Historically important stages in the development of metrology:
18th century- establishing standard meters(the reference is stored in France, at the Museum of Weights and Measures; is now more of a historical exhibit than a scientific instrument);
1832 year - creation Carl Gauss absolute systems of units;
1875 year - signing of the international Metric convention;
1960 year - development and establishment International system of units (SI);
20th century- metrological studies of individual countries are coordinated by International metrological organizations.
Vekhiotchestvenny history of metrology:
accession to the Meter Convention;
1893 year - creation D. I. Mendeleev Main Chamber of Weights and Measures(modern name: «Research Institute of Metrology named after A.I. Mendeleev").
Metrology as a science and field of practice arose in ancient times. The basis of the system of measures in ancient Russian practice was the ancient Egyptian units of measurement, and they, in turn, were borrowed from ancient Greece and Rome. Naturally, each system of measures differed in its own characteristics, connected not only with the era, but also with the national mentality.
The names of the units and their sizes corresponded to the possibility of carrying out measurements by "improvised" methods, without resorting to special devices. So, in Russia, the main units of length were the span and cubit, and the span served as the main ancient Russian measure of length and meant the distance between the ends of the thumb and forefinger of an adult. Later, when another unit appeared - arshin - span (1/4 arshin) gradually fell into disuse.
The measure cubit came to us from Babylon and meant the distance from the bend of the elbow to the end of the middle finger of the hand (sometimes a clenched fist or thumb).
Since the 18th century in Russia, an inch, borrowed from England (it was called "finger"), as well as the English foot, began to be used. A special Russian measure was a sazhen, equal to three cubits (about 152 cm) and an oblique sazhen (about 248 cm).
By decree of Peter I, Russian measures of length were agreed with English ones, and this is essentially the first step in harmonizing Russian metrology with European.
The metric system of measures was introduced in France in 1840. The great importance of its adoption in Russia was emphasized by D.I. Mendeleev, predicting the great role of the universal spread of the metric system as a means of promoting the "future desired rapprochement of peoples."
With the development of science and technology, new measurements and new units of measurement were required, which in turn stimulated the improvement of fundamental and applied metrology.
Initially, the prototype of units of measurement was sought in nature, studying macro-objects and their movement. So, a second began to be considered a part of the period of rotation of the Earth around its axis. Gradually, the search moved to the atomic and intra-atomic level. As a result, the "old" units (measures) were refined and new ones appeared. So, in 1983, a new definition of the meter was adopted: this is the length of the path traveled by light in vacuum in 1/299792458 of a second. This became possible after the speed of light in vacuum (299792458 m/s) was accepted by metrologists as a physical constant. It is interesting to note that now, from the point of view of metrological rules, the meter depends on the second.
In 1988, new constants were adopted at the international level in the field of measurements of electrical units and quantities, and in 1989 a new International Practical Temperature Scale ITS-90 was adopted.
These few examples show that metrology as a science is developing dynamically, which naturally contributes to the improvement of measurement practice in all other scientific and applied fields.
The rapid development of science, engineering and technology in the twentieth century required the development of metrology as a science. In the USSR, metrology developed as a state discipline, because the need to improve the accuracy and reproducibility of measurements grew with the industrialization and growth of the military-industrial complex. Foreign metrology also started from the requirements of practice, but these requirements came mainly from private firms. An indirect consequence of this approach was the state regulation of various concepts related to metrology, that is GOST anything that needs to be standardized. Abroad, this task was undertaken by non-governmental organizations, for example ASTM. Due to this difference in the metrology of the USSR and the post-Soviet republics, state standards (standards) are recognized as dominant, in contrast to the competitive Western environment, where a private company may not use a poorly proven standard or device and agree with its partners on another option for certifying the reproducibility of measurements.
Metrology objects.
Measurements as the main object of metrology are associated with both physical quantities and quantities related to other sciences (mathematics, psychology, medicine, social sciences, etc.). Next, concepts related to physical quantities will be considered.
Physical quantity . This definition means a property that is qualitatively common to many objects, but quantitatively individual for each object. Or, following Leonhard Euler, "a quantity is everything that can increase or decrease, or that to which something can be added or from which it can be taken away."
In general, the concept of "value" is multi-species, that is, it refers not only to physical quantities that are objects of measurement. Quantities include the amount of money, ideas, etc., since the definition of magnitude is applicable to these categories. For this reason, in the standards (GOST-3951-47 and GOST-16263-70) only the concept of a "physical quantity" is given, that is, a quantity that characterizes the properties of physical objects. In measurement technology, the adjective "physical" is usually omitted.
Unit of physical quantity - a physical quantity, which, by definition, is given a value equal to one. Referring once again to Leonhard Euler: "It is impossible to determine or measure one quantity otherwise than by taking as known another quantity of the same kind and indicating the ratio in which it is to it." In other words, in order to characterize any physical quantity, one must arbitrarily choose some other quantity of the same kind as a unit of measurement.
Measure - a carrier of the size of a unit of physical quantity, i.e. a measuring instrument designed to reproduce the physical quantity of a given size. Typical examples of measures are weights, tape measures, rulers. In other types of measurements, measures can have the form of a prism, substances with known properties, etc. When considering certain types of measurements, we will specifically dwell on the problem of creating measures.
The concept of a system of units. Off-system units. Natural systems of units.
Unit system - a set of basic and derived units related to a certain system of quantities and formed in accordance with accepted principles. The system of units is built on the basis of physical theories that reflect the interconnection of physical quantities existing in nature. When determining the units of the system, such a sequence of physical relationships is selected in which each following expression contains only one new physical quantity. This allows you to define the unit of a physical quantity through a set of previously defined units, and ultimately through the main (independent) units of the system (see Fig. Units of physical quantities).
In the first Systems of Units, units of length and mass were chosen as the main ones, for example, in the UK, the foot and the English pound, in Russia, the arshin and the Russian pound. These systems included multiples and submultiples, which had their own names (yard and inch - in the first system, sazhen, vershok, foot and others - in the second), due to which a complex set of derived units was formed. The inconveniences in the sphere of trade and industrial production associated with the difference in national systems of units prompted the idea of developing the metric system of measures (18th century, France), which served as the basis for the international unification of units of length (meter) and mass (kilogram), as well as the most important derived units (area, volume, density).
In the 19th century, K. Gauss and V.E. Weber proposed a system of units for electrical and magnetic quantities, which Gauss called absolute.
In it, the millimeter, milligram, and second were taken as the basic units, and the derived units were formed according to the equations of connection between the quantities in their simplest form, that is, with numerical coefficients equal to one (such systems were later called coherent). In the 2nd half of the 19th century, the British Association for the Advancement of Sciences adopted two systems of units: CGSE (electrostatic) and CGSM (electromagnetic). This laid the foundation for the formation of other Systems of Units, in particular, the symmetric CGS system (which is also called the Gaussian system), the technical system (m, kgf, sec; see. MKGSS system of units),MTS system of units other. In 1901, the Italian physicist G. Giorgi proposed a System of Units based on the meter, kilogram, second, and one electrical unit (the ampere was later chosen; see below). MKSA system of units). The system included units that have become widespread in practice: ampere, volt, ohm, watt, joule, farad, henry. This idea was the basis adopted in 1960 by the 11th General Conference on Weights and Measures International system of units (SI). The system has seven basic units: meter, kilogram, second, ampere, kelvin, mole, candela. The creation of the SI opened up the prospect of a general unification of units and resulted in the adoption by many countries of the decision to switch to this system or to use it predominantly.
Along with practical systems of units, physics uses systems based on universal physical constants, such as the speed of light in a vacuum, the charge of an electron, Planck's constant, and others.
Off-system units , units of physical quantities that are not included in any of the systems of units. Non-systemic units were chosen in separate areas of measurements without regard to the construction of systems of units. Non-systemic units can be divided into independent (defined without the help of other units) and arbitrarily chosen, but defined through other units. The former include, for example, degrees Celsius, defined as 0.01 of the interval between the boiling points of water and the melting of ice at normal atmospheric pressure, the full angle (turn) and others. The latter include, for example, the power unit - horsepower (735.499 W), pressure units - technical atmosphere (1 kgf / cm 2), millimeter of mercury (133.322 n / m 2), bar (10 5 n / m 2) and other. In principle, the use of off-system units is undesirable, since the inevitable recalculations require time and increase the likelihood of errors.
Natural systems of units , systems of units in which fundamental physical constants are taken as basic units - such as, for example, the gravitational constant G, the speed of light in vacuum c, Planck's constant h, Boltzmann's constant k, Avogadro's number N A , electron charge e, electron rest mass m e and other. The size of the basic units in the Natural Systems of Units is determined by the phenomena of nature; In this, natural systems fundamentally differ from other systems of units, in which the choice of units is determined by the requirements of measurement practice. According to the idea of M. Planck, who first (1906) proposed the Natural Systems of Units with the basic units h, c, G, k, it would be independent of terrestrial conditions and suitable for any time and place in the Universe.
A number of other Natural Systems of Units has been proposed (G. Lewis, D. Hartree, A. Ruark, P. Dirac, A. Gresky, and others). Natural systems of units are characterized by extremely small sizes of units of length, mass and time (for example, in the Planck system - respectively 4.03 * 10 -35 m, 5.42 * 10 -8 kg and 1.34 * 10 -43 sec) and , on the contrary, the enormous dimensions of the temperature unit (3.63 * 10 32 C). As a result, the Natural Systems of Units are inconvenient for practical measurements; in addition, the accuracy of reproduction of units is several orders of magnitude lower than the basic units of the International System (SI), as it is limited by the accuracy of knowledge of physical constants. However, in theoretical physics, the use of the Natural Systems of Units sometimes makes it possible to simplify the equations and gives some other advantages (for example, the Hartree system makes it possible to simplify the writing of the equations of quantum mechanics).
Units of physical quantities.
Units of physical quantities - specific physical quantities, which, by definition, are assigned numerical values equal to 1. Many Units of physical quantities are reproduced by the measures used for measurements (for example, meter, kilogram). In the early stages of the development of material culture (in slave and feudal societies), there were units for a small range of physical quantities - length, mass, time, area, volume. Units of physical quantities were chosen without connection with each other, and, moreover, different in different countries and geographical areas. So a large number of often identical in name, but different in size units - cubits, feet, pounds - arose. With the expansion of trade relations between peoples and the development of science and technology, the number of Units of physical quantities increased and the need for the unification of units and the creation of systems of units was increasingly felt. On Units of physical quantities and their systems began to conclude special international agreements. In the 18th century, the metric system of measures was proposed in France, which later received international recognition. On its basis, a number of metric systems of units were built. Currently, there is a further ordering of the Units of physical quantities on the basis of International system of units(SI).
Units of physical quantities are divided into system units, that is, included in any system of units, and off-system units (e.g., mmHg, horsepower, electron volt). System Units of physical quantities are divided into basic, chosen arbitrarily (meter, kilogram, second, etc.), and derivatives, formed according to the equations of connection between quantities (meter per second, kilogram per cubic meter, newton, joule, watt, etc. ). For the convenience of expressing quantities that are many times larger or smaller than units of physical quantities, multiple units and submultiple units are used. In metric systems of units, multiples and submultiples Units of physical quantities (with the exception of units of time and angle) are formed by multiplying the system unit by 10 n, where n is a positive or negative integer. Each of these numbers corresponds to one of the decimal prefixes used to form multiples and submultiples.
International system of units.
International system of units (Systeme International d "Unitees), a system of units of physical quantities adopted by the 11th General Conference on Weights and Measures (1960). The abbreviation for the system is SI (in Russian transcription - SI). The international system of units was developed to replace a complex set of systems units and individual non-systemic units, established on the basis of the metric system of measures, and simplifying the use of units.The advantages of the International System of Units are its universality (covers all branches of science and technology) and coherence, i.e., the consistency of derived units that are formed according to equations that do not containing coefficients of proportionality Due to this, when calculating the values of all quantities in units of the International System of Units, it is not necessary to enter coefficients in the formulas that depend on the choice of units.
The table below shows the names and designations (international and Russian) of the main, additional and some derived units of the International System of Units. Russian designations are given in accordance with the current GOSTs; the designations provided for by the draft new GOST "Units of physical quantities" are also given. The definition of basic and additional units and quantities, the ratios between them are given in the articles about these units.
The first three basic units (meter, kilogram, second) allow the formation of coherent derived units for all quantities of a mechanical nature, the rest are added to form derived units of quantities that are not reducible to mechanical ones: ampere - for electrical and magnetic quantities, kelvin - for thermal, candela - for light and mole - for quantities in the field of physical chemistry and molecular physics. Additional, units of radians and steradians are used to form derived units of quantities that depend on flat or solid angles. To form the names of decimal multiples and submultiples, special SI prefixes are used: deci (to form units equal to 10 -1 in relation to the original), centi (10 -2), milli (10 -3), micro (10 -6), nano (10 -9), pico (10 -12), femto (10 -15), atto (10 -18), deca (10 1), hecto (10 2), kilo (10 3), mega (10 6 ), giga (10 9), tera (10 12).
Unit systems: MKGSS, ISS, ISSA, MKSK, MTS, SGS.
MKGSS system of units (MkGS system), a system of units of physical quantities, the main units of which are: meter, kilogram-force, second. It entered practice at the end of the 19th century, was admitted to the USSR by OST VKS 6052 (1933), GOST 7664-55 and GOST 7664-61 "Mechanical units". The choice of the unit of force as one of the basic units led to the widespread use of a number of units of the MKGSS system of units (mainly units of force, pressure, mechanical stress) in mechanics and technology. This system is often referred to as the engineering system of units. For a unit of mass in the MKGSS system of units, the mass of a body acquiring an acceleration of 1 m / s 2 under the action of a force of 1 kgf applied to it is taken. This unit is sometimes called the engineering unit of mass (i.e. m) or inertia. 1 tu = 9.81 kg. The MKGSS system of units has a number of significant drawbacks: inconsistency between mechanical and practical electrical units, the absence of a kilogram-force standard, the rejection of the common unit of mass - the kilogram (kg) and, as a result (in order not to use i.e. m.) - the formation of quantities with the participation of weight instead of mass (specific gravity, weight consumption, etc.), which sometimes led to a confusion of the concepts of mass and weight, the use of the designation kg instead of kgf, etc. These shortcomings led to the adoption of international recommendations on the abandonment of the ICSC system of units and on the transition to International system of units(SI).
ISS system of units (MKS system), a system of units of mechanical quantities, the main units of which are: meter, kilogram (unit of mass), second. It was introduced in the USSR by GOST 7664-55 "Mechanical units", replaced by GOST 7664-61. It is also used in acoustics in accordance with GOST 8849-58 "Acoustic units". The ISS system of units is included as part of International system of units(SI).
MKSA system of units (MKSA system), a system of units of electrical and magnetic quantities, the main units of which are: meter, kilogram (unit of mass), second, ampere. The principles for constructing the MKSA systems of units were proposed in 1901 by the Italian scientist G. Giorgi, so the system also has a second name - the Giorgi system of units. The MKSA system of units is used in most countries of the world, in the USSR it was established by GOST 8033-56 "Electric and magnetic units". The MKSA system of units includes all practical electrical units that have already become widespread: ampere, volt, ohm, pendant, etc .; The MKSA system of units is included as an integral part in International system of units(SI).
MKSK system of units (MKSK system), system of units of thermal quantities, osn. the units of which are: meter, kilogram (a unit of mass), second, Kelvin (a unit of thermodynamic temperature). The use of the MKSK system of units in the USSR is established by GOST 8550-61 "Thermal Units" (in this standard, the former name of the unit of thermodynamic temperature - "degree Kelvin", changed to "Kelvin" in 1967 by the 13th General Conference on Weights and Measures) is still used. In the MKSK system of units, two temperature scales are used: the thermodynamic temperature scale and the International Practical Temperature Scale (IPTS-68). Along with Kelvin, the degree Celsius, denoted °C and equal to kelvin (K), is used to express thermodynamic temperature and temperature difference. As a rule, below 0 ° C, the Kelvin temperature T is given, above 0 ° C, the Celsius temperature t (t \u003d T-To, where To \u003d 273.15 K). IPTS-68 also distinguishes between the international practical temperature of Kelvin (symbol T 68) and the international practical temperature of Celsius (t 68); they are related by the ratio t 68 = T 68 - 273.15 K. The units of T 68 and t 68 are, respectively, Kelvin and degrees Celsius. The names of derived thermal units can include both Kelvin and degrees Celsius. MKSK system of units is included as an integral part in International system of units(SI).
MTS system of units (MTS system), a system of units of physical quantities, the main units of which are: meter, ton (unit of mass), second. It was introduced in France in 1919, in the USSR - in 1933 (cancelled in 1955 due to the introduction of GOST 7664-55 "Mechanical units"). The MTC system of units was constructed similarly to that used in physics cgs system of units and was intended for practical measurements; for this purpose, large units of length and mass were chosen. The most important derived units: forces - walls (SN), pressure - pieza (pz), work - wall meter, or kilojoule (kJ), power - kilowatt (kW).
cgs system of units , a system of units of physical quantities. in which three basic units are accepted: length - centimeter, mass - gram and time - second. The system with the basic units of length, mass and time was proposed by the Committee on Electrical Standards of the British Association for the Development of Sciences, formed in 1861, which included prominent physicists of that time (W. Thomson (Kelvin), J. Maxwell, C. Wheatstone and others .), as a system of units covering mechanics and electrodynamics. After 10 years, the association formed a new committee, which finally chose the centimeter, gram and second as the basic units. The first International Congress of Electricians (Paris, 1881) also adopted the CGS system of units, and since then it has been widely used in scientific research. With the introduction of the International System of Units (SI), in scientific papers in physics and astronomy, along with SI units, it is allowed to use CGS units of the system of units.
The most important derived units of the CGS system of units in the field of mechanical measurements include: a unit of speed - cm / sec, acceleration - cm / sec 2, force - dyne (dyne), pressure - dyne / cm 2, work and energy - erg, power - erg / sec, dynamic viscosity - poise (pz), kinematic viscosity - stock (st).
For electrodynamics, two CGS systems of units were initially adopted - electromagnetic (CGSM) and electrostatic (CGSE). The construction of these systems was based on the Coulomb law - for magnetic charges (CGSM) and electric charges (CGSE). Since the 2nd half of the 20th century, the so-called symmetric CGS system of units has become most widespread (it is also called the mixed or Gaussian system of units).
Legal basis for ensuring the uniformity of measurements.
The metrological services of government authorities and legal entities organize their activities on the basis of the provisions of the Laws "On Ensuring the Uniformity of Measurements", "On Technical Regulation" (formerly - "On Standardization", "On Certification of Products and Services"), as well as resolutions of the Government of the Russian Federation, administrative acts of subjects of the federation, regions and cities, regulatory documents of the State system for ensuring the uniformity of measurements and resolutions of the State Standard of the Russian Federation.
In accordance with the current legislation, the main tasks of metrological services include ensuring the unity and required accuracy of measurements, increasing the level of metrological support for production, and exercising metrological control and supervision through the following methods:
calibration of measuring instruments;
supervision over the condition and use of measuring instruments, certified methods for performing measurements, standards of units of quantities used for calibrating measuring instruments, compliance with metrological rules and norms;
issuance of mandatory instructions aimed at preventing, stopping or eliminating violations of metrological rules and norms;
checking the timeliness of submission of measuring instruments for testing in order to approve the type of measuring instruments, as well as for verification and calibration. In Russia, the Model Regulations on metrological services have been adopted. This Regulation determines that the metrological service of the state governing body is a system formed by the order of the head of the state governing body, which may include:
structural subdivisions (service) of the chief metrologist in the central office of the state governing body;
head and base organizations of the metrological service in industries and sub-sectors, appointed by the state governing body;
metrological services of enterprises, associations, organizations and institutions.
December 27, 2002 a fundamentally new strategic Federal Law “On Technical Regulation” was adopted, which regulates relations arising from the development, adoption, application and implementation of mandatory and voluntary requirements for products, production processes, operation, storage, transportation, sale, disposal, performance of work and provision services, as well as in conformity assessment (technical regulations and standards should ensure the practical implementation of legislative acts).
The introduction of the Law "On Technical Regulation" is aimed at reforming the system of technical regulation, standardization and quality assurance and is caused by the development of market relations in society.
Technical regulation - legal regulation of relations in the field of establishing, applying and using mandatory requirements for products, production processes, operation, storage, transportation, sale and disposal, as well as in the field of establishing and applying on a voluntary basis requirements for products, production processes, operation, storage, transportation, sale and disposal, performance of work and provision of services and legal regulation of relations in the field of conformity assessment.
Technical regulation should be carried out in accordance with principles:
application of uniform rules for establishing requirements for products, production processes, operation, storage, transportation, sale and disposal, performance of work and provision of services;
compliance of technical regulation with the level of development of the national economy, the development of the material and technical base, as well as the level of scientific and technical development;
independence of accreditation bodies, certification bodies from manufacturers, sellers, performers and purchasers;
unified system and rules of accreditation;
the unity of the rules and methods of research, testing and measurement in the course of mandatory conformity assessment procedures;
unity of application of the requirements of technical regulations, regardless of the features and types of transactions;
the inadmissibility of restricting competition in the implementation of accreditation and certification;
the inadmissibility of combining the powers of state control (supervision) bodies and certification bodies;
the inadmissibility of combining the powers of accreditation and certification by one body;
inadmissibility of off-budget financing of state control (supervision) over compliance with technical regulations.
One of the main ideas of the law thing is:
mandatory requirements contained today in regulations, including state standards, are included in the field of technical legislation - in federal laws (technical regulations);
a two-level structure of regulatory and regulatory documents is being created: technical regulation(contains mandatory requirements) and standards(contain voluntary norms and rules harmonized with the technical regulations).
The developed program for reforming the standardization system in the Russian Federation was designed for 7 years (until 2010), during which time it was necessary to:
develop 450-600 technical regulations;
remove mandatory requirements from the relevant standards;
revise sanitary rules and regulations (SanPin);
revise building codes and regulations (SNiP), which already in fact are technical regulations.
Significance of the introduction of the Federal Law "On Technical Regulation":
the introduction of the Law of the Russian Federation "On Technical Regulation" fully reflects what is happening today in the world of economic development;
it aims to remove technical barriers to trade;
the law creates conditions for Russia's accession to the World Trade Organization (WTO).
The concept and classification of measurements. Main characteristics of measurements.
Measurement - cognitive process, which consists in comparing a given value with a known value, taken as a unit. Measurements are divided into direct, indirect, cumulative and joint.
Direct measurements - a process in which the desired value of a quantity is found directly from experimental data. The simplest cases of direct measurements are measurements of length with a ruler, temperature with a thermometer, voltage with a voltmeter, etc.
Indirect measurements - type of measurement, the result of which is determined from direct measurements associated with the measured value by a known relationship. For example, the area can be measured as the product of the results of two linear measurements of coordinates, the volume - as the result of three linear measurements. Also, the resistance of an electrical circuit or the power of an electrical circuit can be measured by the values of the potential difference and current strength.
Cumulative measurements - these are measurements in which the result is found according to repeated measurements of one or more quantities of the same name with various combinations of measures or these quantities. For example, cumulative measurements are measurements in which the mass of individual weights of a set is found from the known mass of one of them and from the results of direct comparisons of the masses of various combinations of weights.
Joint measurements name the produced direct or indirect measurements of two or more non-identical quantities. The purpose of such measurements is to establish a functional relationship between quantities. For example, measurements of temperature, pressure and volume occupied by gas, measurements of body length depending on temperature, etc. will be joint.
According to the conditions that determine the accuracy of the result, measurements are divided into three classes:
measuring the highest possible accuracy achievable with the current state of the art;
control and verification measurements performed with a given accuracy;
technical measurements, the error of which is determined by the metrological characteristics of measuring instruments.
Technical measurements define the class of measurements performed under production and operating conditions, when the measurement accuracy is determined directly by the measuring instruments.
Unity of measurements- the state of measurements, in which their results are expressed in legal units and the errors are known with a given probability. The unity of measurements is necessary in order to be able to compare the results of measurements performed at different times, using different methods and means of measurement, as well as in different geographical locations.
The unity of measurements is ensured by their properties: convergence of measurement results; reproducibility of measurement results; the correctness of the measurement results.
Convergence is the proximity of the measurement results obtained by the same method, identical measuring instruments, and the proximity to zero of the random measurement error.
Reproducibility of measurement results characterized by the closeness of the measurement results obtained by different measuring instruments (of course, the same accuracy) by different methods.
Accuracy of measurement results is determined by the correctness of both the measurement methods themselves and the correctness of their use in the measurement process, as well as the closeness to zero of the systematic measurement error.
Accuracy of measurements characterizes the quality of measurements, reflecting the proximity of their results to the true value of the measured quantity, i.e. proximity to zero measurement errors.
The process of solving any measurement problem includes, as a rule, three stages:
training,
measurement (experiment);
processing results. In the process of carrying out the measurement itself, the object of measurement and the means of measurement are brought into interaction. measuring tool - a technical tool used in measurements and having normalized metrological characteristics. Measuring instruments include measures, measuring instruments, measuring installations, measuring systems and transducers, standard samples of the composition and properties of various substances and materials. According to the temporal characteristics, the measurements are divided into:
static, in which the measured value remains unchanged over time;
dynamic, during which the measured value changes.
According to the way of expressing the results of measurement, they are divided into:
absolute, which are based on direct or indirect measurements of several quantities and on the use of constants, and as a result of which the absolute value of the quantity in the corresponding units is obtained;
relative measurements, which do not allow you to directly express the result in legal units, but allow you to find the ratio of the measurement result to any quantity of the same name with an unknown value in some cases. For example, it can be relative humidity, relative pressure, elongation, etc.
The main characteristics of measurements are: principle of measurement, method of measurement, error, accuracy, reliability and correctness of measurements.
Measuring principle - a physical phenomenon or a combination of them, which are the basis of measurements. For example, mass can be measured based on gravity, or it can be measured based on inertial properties. Temperature can be measured by the thermal radiation of a body or by its effect on the volume of some liquid in a thermometer, etc.
Measurement method - a set of principles and means of measurement. In the example mentioned above with temperature measurement, measurements by thermal radiation are referred to as a non-contact thermometry method, measurements with a thermometer are a contact thermometry method.
Measurement error - the difference between the value of the quantity obtained during the measurement and its true value. The measurement error is associated with the imperfection of methods and measuring instruments, with insufficient experience of the observer, with extraneous influences on the measurement result. The causes of errors and ways to eliminate or minimize them are discussed in detail in a special chapter, since the assessment and accounting for measurement errors is one of the most important sections of metrology.
Accuracy of measurements - measurement characteristic, reflecting the proximity of their results to the true value of the measured quantity. Quantitatively, the accuracy is expressed by the reciprocal of the modulus of the relative error, i.e.
where Q is the true value of the measured quantity, D is the measurement error equal to
(2)
where X is the measurement result. If, for example, the relative measurement error is 10 -2%, then the accuracy will be 10 4 .
The correctness of measurements is the quality of measurements, reflecting the closeness to zero of systematic errors, i.e., errors that remain constant or regularly change during the measurement process. The correctness of measurements depends on how correctly (correctly) the methods and means of measurement were chosen.
Measurement reliability - a characteristic of the quality of measurements, dividing all the results into reliable and unreliable, depending on whether the probabilistic characteristics of their deviations from the true values of the corresponding quantities are known or unknown. Measurement results, the reliability of which is unknown, can serve as a source of misinformation.
Measuring instruments.
Measuring instrument (SI) - a technical tool intended for measurements, having normalized metrological characteristics, reproducing or storing a unit of physical quantity, the size of which is taken unchanged over a known time interval.
The above definition expresses the essence of the measuring instrument, which, firstly, stores or reproduces a unit, secondly, this unit unchanged. These most important factors determine the possibility of carrying out measurements, i.e. make a technical tool a means of measurement. This means of measurement differs from other technical devices.
Measuring instruments include measures, measuring: transducers, instruments, installations and systems.
Measure of a physical quantity- a measuring instrument designed to reproduce and (or) store a physical quantity of one or more specified dimensions, the values of which are expressed in established units and are known with the required accuracy. Examples of measures: weights, measuring resistors, gauge blocks, radionuclide sources, etc.
Measures that reproduce physical quantities of only one size are called unambiguous(weight), several sizes – polysemantic(millimeter ruler - allows you to express the length in both mm and cm). In addition, there are sets and magazines of measures, for example, a magazine of capacitances or inductances.
When measuring using measures, the measured values are compared with known values that are reproducible by the measures. Comparison is carried out in different ways, the most common means of comparison is comparator, designed to compare measures of homogeneous quantities. An example of a comparator is a balance scale.
Measures include standard samples and reference substance, which are specially designed bodies or samples of a substance of a certain and strictly regulated content, one of the properties of which is a quantity with a known value. For example, samples of hardness, roughness.
Measuring transducer (IP) - a technical tool with normative metrological characteristics that is used to convert a measured quantity into another quantity or a measuring signal that is convenient for processing, storage, indication or transmission. Measurement information at the output of the IP, as a rule, is not available for direct perception by the observer. Although IPs are structurally separate elements, they are most often included as components in more complex measuring instruments or installations and do not have independent significance during measurements.
The value to be converted, supplied to the measuring transducer, is called input, and the result of the transformation is day off size. The ratio between them is given conversion function, which is its main metrological characteristic.
For direct reproduction of the measured value, primary converters, which are directly affected by the measured value and in which the measured value is transformed for its further transformation or indication. An example of a primary transducer is a thermocouple in a thermoelectric thermometer circuit. One of the types of primary converter is sensor– Structurally isolated primary transducer, from which measuring signals are received (it “gives” information). The sensor can be placed at a considerable distance from the measuring instrument that receives its signals. For example, a weather probe sensor. In the field of ionizing radiation measurements, a detector is often referred to as a sensor.
By the nature of the transformation, IP can be analog, analog-to-digital (ADC), digital-to-analog (DAC), that is, converting a digital signal into an analog one or vice versa. In the analog form of representation, the signal can take on a continuous set of values, that is, it is a continuous function of the measured value. In digital (discrete) form, it is represented as digital groups or numbers. Examples of IP are measuring current transformer, resistance thermometers.
Measuring device- a measuring instrument designed to obtain the values of the measured physical quantity in the specified range. The measuring device presents measurement information in a form accessible to direct perception observer.
By indication method distinguish indicating and recording instruments. Registration can be carried out in the form of a continuous record of the measured value or by printing instrument readings in digital form.
Devices direct action display the measured value on the indicating device, which has a graduation in units of this value. For example, ammeters, thermometers.
Comparison devices are designed to compare measured quantities with quantities whose values are known. Such devices are used for measurements with greater accuracy.
Measuring instruments are divided into integrating and summing, analog and digital, self-recording and printing.
Measuring setup and system- a set of functionally combined measures, measuring instruments and other devices designed to measure one or more quantities and located in one place ( installation) or in different places of the measurement object ( system). Measuring systems are usually automated and in essence they provide automation of measurement processes, processing and presentation of measurement results. An example of measuring systems are automated radiation monitoring systems (ASRK) at various nuclear physics facilities, such as, for example, nuclear reactors or charged particle accelerators.
By metrological purpose measuring instruments are divided into working and standards.
Working SI- a measuring instrument intended for measurements, not related to the transfer of the size of the unit to other measuring instruments. The working measuring instrument can also be used as an indicator. Indicator- a technical tool or substance designed to establish the presence of any physical quantity or exceed the level of its threshold value. The indicator does not have standardized metrological characteristics. Examples of indicators are an oscilloscope, litmus paper, etc.
Reference- a measuring instrument designed to reproduce and (or) store a unit and transfer its size to other measuring instruments. Among them are working standards different categories, which were previously called exemplary measuring instruments.
The classification of measuring instruments is also carried out according to various other criteria. For example, by types of measured values, by type of scale (with a uniform or non-uniform scale), by connection with the object of measurement (contact or non-contact
When performing various works on the metrological support of measurements, specific categories are used, which also need to be defined. These categories are:
Certification - verification of metrological characteristics (measurement errors, accuracy, reliability, correctness) of a real measuring instrument.
Certification - checking the compliance of the measuring instrument with the standards of a given country, a given industry with the issuance of a document-certificate of conformity. During certification, in addition to metrological characteristics, all items contained in the scientific and technical documentation for this measuring instrument are subject to verification. These may be requirements for electrical safety, for environmental safety, for the impact of changes in climatic parameters. It is obligatory to have methods and means of verification of this measuring instrument.
Verification - periodic control of errors in the readings of measuring instruments for measuring instruments of a higher accuracy class (exemplary instruments or exemplary measure). As a rule, verification ends with the issuance of a certificate of verification or branding of the measuring instrument or the measure being verified.
graduation - making marks on the scale of the device or obtaining the dependence of the readings of a digital indicator on the value of the measured physical quantity. Often in technical measurements, calibration is understood as periodic monitoring of the device's performance by measures that do not have a metrological status or by special devices built into the device. Sometimes this procedure is called calibration, and this word is written on the instrument's operating panel.
This term is actually used in metrology, and a slightly different procedure is called calibration according to standards.
Calibrate a measure or set of measures - verification of a set of unambiguous measures or a multi-valued measure at different scale marks. In other words, calibration is the verification of a measure through cumulative measurements. Sometimes the term "calibration" is used as a synonym for verification, however, calibration can only be called such verification, in which several measures or divisions of the scale are compared with each other in various combinations.
Reference - a measuring instrument designed to reproduce and store a unit of quantity in order to transfer it to the means of measuring a given quantity.
primary standard ensures the reproducibility of the unit under special conditions.
secondary standard– standard, the unit size obtained by comparison with the primary standard.
Third standard- comparison standard - this secondary standard is used to compare the standard, which for one reason or another cannot be compared with each other.
Fourth standard– The working standard is used to directly convey the size of the unit.
Means of verification and calibration.
Verification of the measuring instrument- a set of operations performed by the bodies of the state metrological service (other authorized bodies, organizations) in order to determine and confirm the compliance of the measuring instrument with the established technical requirements.
Measuring instruments subject to state metrological control and supervision are subject to verification upon release from production or repair, upon import and operation.
Calibration of the measuring instrument- a set of operations performed in order to determine the actual values of metrological characteristics and (or) suitability for use of a measuring instrument that is not subject to state metrological control and supervision. Measuring instruments that are not subject to verification may be subjected to calibration upon release from production or repair, upon import and operation.
VERIFICATION measuring instruments - a set of operations performed by the bodies of the state metrological service (other authorized bodies, organizations) in order to determine and confirm the compliance of the measuring instrument with the established technical requirements.
Responsibility for improper performance of verification work and non-compliance with the requirements of the relevant regulatory documents is borne by the relevant body of the State Metrological Service or the legal entity whose metrological service performed the verification work.
Positive results of verification of measuring instruments are certified by a verification mark or verification certificate.
The form of the verification mark and verification certificate, the procedure for applying the verification mark is established by the Federal Agency for Technical Regulation and Metrology.
In Russia, verification activities are regulated by the Law of the Russian Federation "On Ensuring the Uniformity of Measurements" and many other by-laws.
Verification- determination of the suitability of measuring equipment falling under the State Metrological Supervision for use by monitoring their metrological characteristics.
Interstate Council for Standardization, Metrology and Certification (countries CIS) the following types of verification are established
Primary verification - verification performed when a measuring instrument is released from production or after repair, as well as when a measuring instrument is imported from abroad in batches, upon sale.
Periodic verification - verification of measuring instruments that are in operation or in storage, performed at established calibration intervals.
Extraordinary verification - Verification of a measuring instrument, carried out before the deadline for its next periodic verification.
Inspection verification - verification carried out by the body state metrological service during the state supervision over the condition and use of measuring instruments.
Complete verification - verification, in which they determine metrological characteristics means of measurement inherent in it as a whole.
Element-by-element verification is a verification in which the values of the metrological characteristics of measuring instruments are established according to the metrological characteristics of its elements or parts.
Selective verification - verification of a group of measuring instruments selected randomly from a batch, the results of which are used to judge the suitability of the entire batch.
Verification schemes.
To ensure the correct transfer of the dimensions of the units of measurement from the standard to the working measuring instruments, verification schemes are drawn up that establish the metrological subordination of the state standard, bit standards and working measuring instruments.
Verification schemes are divided into state and local. State verification schemes apply to all measuring instruments of this type used in the country. Local verification schemes are intended for metrological bodies of ministries, they also apply to measuring instruments of subordinate enterprises. In addition, a local scheme for measuring instruments used in a particular enterprise can also be drawn up. All local verification schemes must comply with the requirements of subordination, which is defined by the state verification scheme. State verification schemes are developed by research institutes of the State Standard of the Russian Federation, holders of state standards.
In some cases, it is impossible to reproduce the entire range of values with one standard, therefore, several primary standards can be provided in the circuit, which together reproduce the entire measurement scale. For example, the temperature scale from 1.5 to 1 * 10 5 K is reproduced by two state standards.
Verification scheme for measuring instruments - a regulatory document that establishes the subordination of measuring instruments involved in the transfer of the unit size from the reference to working measuring instruments (indicating methods and errors during transmission). There are state and local verification schemes, previously there were also departmental PSs.
The state verification scheme applies to all means of measuring a given physical quantity used in the country, for example, to means of measuring electrical voltage in a certain frequency range. Establishing a multi-stage procedure for transferring the size of a PV unit from the state standard, requirements for means and methods of verification, the state verification scheme is, as it were, a structure of metrological support for a certain type of measurement in the country. These schemes are developed by the main centers of standards and are issued by one GOST GSI.
Local verification schemes apply to measuring instruments subject to verification in a given metrological unit at an enterprise that has the right to verify measuring instruments and are drawn up in the form of an enterprise standard. Departmental and local verification schemes should not contradict the state ones and should take into account their requirements in relation to the specifics of a particular enterprise.
The departmental verification scheme is developed by the body of the departmental metrological service, coordinated with the main center of standards - the developer of the state verification scheme for measuring instruments of this PV and applies only to measuring instruments subject to intradepartmental verification.
Metrological characteristics of measuring instruments.
The metrological characteristic of a measuring instrument is a characteristic of one of the properties of a measuring instrument that affects the measurement result or its error. The main metrological characteristics are the range of measurements and various components of the error of the measuring instrument.
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SECONDARY VOCATIONAL EDUCATION
METROLOGY,
STANDARDIZATION
AND CERTIFICATION
IN ENERGY
federal government agency
"Federal Institute for the Development of Education"
as a teaching aid for use in the educational process
educational institutions implementing secondary vocational education programs
ACADEMIA
Moscow Publishing Center "Academy"2009 UDC 389(075.32) BBK 30.10ya723 M576 Reviewer - teacher of the disciplines "Metrology, standardization and certification and" Metrological support "GOU SPO Electromechanical College No. 55 allowance for students. avg. prof. education / [S. A. Zaitsev, A.N. Tolstoy, D.D. Gribanov, R. V. Merkulov]. - M. : Iz publishing center "Academy", 2009. - 224 p.
ISBN 978-5-7695-4978- The fundamentals of metrology and metrological support are considered: terms, physical quantities, fundamentals of the theory of measurements, means of measurement and control, metrological characteristics, measurements and control of electrical and magnetic quantities. The basics of standardization are outlined: the history of development, the legal framework, international, regional and domestic, unification and aggregation, product quality. Particular attention is paid to the basics of certification and conformity assessment.
For students of secondary vocational schools.
UDC 389(075.32) B B K October 30 The original layout of this publication is the property of the Academy Publishing Center. and its reproduction in any way without the consent of the copyright holder is prohibited © Zaitsev S.A.. Tolstov A.N., Gribanov D.D.. M erkulov R.V., © Educational and Publishing Center "Academy", ISBN 978-5-7695 -4978-6 © Design Publishing Center "Academy",
FOREWORD
Modern technology and the prospects for its development, constantly increasing requirements for the quality of products predetermine the need to obtain and use knowledge that is basic, i.e.E. basic for all specialists working at the stage of design development, and at the stage of its manufacture, and at the stages of operation and maintenance, regardless of departmental affiliation. This knowledge will be in demand both in general machine building, in power machine building, and in many other areas. These basic materials are covered in this tutorial. The material presented in the textbook is not isolated from other disciplines studied in an educational institution. The knowledge gained in the course of studying a number of disciplines, for example, "Mathematics", "Physics", will be useful in mastering the issues of metrology, standardization, conformity assessment, interchangeability. Knowledge, skills and practical skills after studying this educational material will be in demand throughout the entire period of work after graduation, regardless of the place of work, whether it is the field of production or service, or the field of trade in technical mechanisms or machines.
Chapter I presents the basic concepts of the science of "Metrology", considers the fundamentals of the theory of measurements, means of measuring and controlling electrical and magnetic quantities, issues of metrological support and uniformity of measurements.
Chapter 2 talks about the standardization system in the Russian Federation, systems of standards, unification and aggregation, issues of interchangeability of parts, assemblies and mechanisms, product quality indicators, quality systems. The material presented in Chapter 3 will allow you to study and practically use knowledge in the field of certification , confirmation of the conformity of products and works, certification of test equipment used in power engineering. For better assimilation of the presented material, control questions are given at the end of each subsection.
The preface, chapter 2 was written by A. N. Tolstov, chapter 1 - by S, A. Zaitsev, R. V, M erkulov, D. D. Gribanov, chapter 3 - by D. D. Gribanov.
BASICS OF METROLOGY AND METROLOGICAL
SECURITIES
Metrology is the science of measurements, methods and means of ensuring their unity and ways to achieve the required accuracy.It originated in ancient times, as soon as a person needed to measure mass, length, time, etc. Moreover, as units of quantities, those that were always “at hand” were used. So, for example, in Russia the length was measured by fingers, elbows, sazhens, etc. These measures are shown in fig. I.I.
The role of metrology has increased enormously in recent decades. It has penetrated and won (in some areas it is winning) a very firm position for itself. Due to the fact that metrology has spread to almost all areas of human activity, metrological terminology is closely related to the terminology of each of the "special" areas. At the same time, something resembling the phenomenon of incompatibility arose. This or that term, acceptable for one area of science or technology, turns out to be unacceptable for another, since in the traditional terminology of another area, the same word can denote a completely different concept. For example, size in relation to clothing can mean "large", "medium", and "small";
the word "linen" can have different meanings: in the textile industry, it is a material (linen); in relation to rail transport, it denotes the path along which this transport moves (railway bed).
In order to restore order in this matter, a state standard for metrological terminology was developed and approved - GOST 16263 “State system for ensuring the uniformity of measurements. Metrology. Terms and Definitions". At present, this GOST has been replaced by RM G 29 - 99 “GSI. M etrology. Terms and Definitions". Further in the textbook, terms and definitions are presented in accordance with this document.
Since the requirements for conciseness are imposed on the terms, they are characterized by a certain conventionality. On the one hand, one should not forget about this and apply the approved terms in accordance with their definition, and on the other hand, the concepts given in the definition should be replaced by other terms.
At present, the object of metrology is all units of measurement of physical quantities (mechanical, electrical, thermal, etc.), all measuring instruments, types and methods of measurements, i.e., everything that is necessary to ensure the uniformity of measurements and the organization of metrological provision at all stages of the life cycle of any products and scientific research, as well as accounting for any resources.
Modern metrology as a science based on the achievements of other sciences, their methods and means of measurement, in turn, contributes to their development. Metrology has penetrated into all areas of human activity, into all sciences and disciplines, and is a single science for all of them. There is not a single area of human activity where one could do without quantitative estimates obtained as a result of measurements.
For example, in 1982, the relative error in determining moisture content, equal to 1%, led to an inaccuracy in determining the annual cost of coal, 73 million rubles, and grain, 60 million rubles.
To make it clearer, metrologists usually give this example:
“There were 100 kg of cucumbers in the warehouse. The measurements carried out showed that their moisture content is 99%, i.e., 100 kg of cucumbers contain 99 kg of water and 1 kg of dry matter. After some time of storage, the moisture content of the same batch of cucumbers was again measured.
The measurement results recorded in the corresponding protocol showed that the humidity decreased to 98%. Since the humidity changed by only 1%, no one had an idea, but what is the mass of the remaining cucumbers? But it turns out that if the humidity became 98%, then exactly half of the cucumbers remained, i.e.
50 kg. And that's why. The amount of dry matter in cucumbers does not depend on moisture, therefore, it has not changed, and as it was 1 kg, 1 kg remains, but if earlier it was 1%, then after storage it became 2%. Having made a proportion, it is easy to determine that there are 50 kg of cucumbers.
In industry, a significant part of the measurements of the composition of a substance is still made using qualitative analysis. The errors of these analyzes are sometimes several times higher than the difference between the amounts of individual components, by which metals of various grades, chemical materials, etc. should differ from each other. As a result, such measurements, it is impossible to achieve the required product quality.
1. What is metrology and why is it given so much attention?
2. What metrology objects do you know?
3. Why measurements are needed?
4. Are measurements without errors possible?
1.2. Physical quantity. Systems of units A physical quantity (PV) is a property that is qualitatively common to many physical objects (physical systems, their states and processes occurring in them), but quantitatively individual for each object. For example, the length of various objects (table, ballpoint pen, car, etc.) can be estimated in meters or fractions of a meter, and each of them - in specific lengths: 0.9 m; 15 cm;
3.3 mm. Examples can be given not only for any properties of physical objects, but also for physical systems, their states and the processes occurring in them.
The term "quantity" is usually applied to those properties or characteristics that can be quantified by physical methods, i.e. can be measured. There are properties or characteristics that science and technology do not currently allow to quantify, such as smell, taste, color. Therefore, such characteristics are usually avoided to be called "quantities", but are called "properties".
In a broad sense, “value” is a multi-species concept. This can be demonstrated by the example of three quantities.
The first example is price, the value of goods expressed in monetary units. Previously, systems of monetary units were an integral part of metrology. It is currently an independent region.
The second example of a variety of quantities can be called the biological activity of medicinal substances. The biological activity of a number of vitamins, antibiotics, hormonal preparations is expressed in International units of biological activity, denoted by I.E.
The third example is physical quantities, i.e. properties inherent in physical objects (physical systems, their states and processes occurring in them). It is these quantities that modern metrology is mainly concerned with.
The size of the PV (the size of the quantity) is the quantitative content in this object of the property corresponding to the concept of "physical quantity" (for example, the size of the length, mass, current strength, etc.).
The term "size" should be used in cases where it is necessary to emphasize that we are talking about the quantitative content of a property in a given object of a physical quantity.
Dimension of PV (dimension of a quantity) is an expression reflecting the relationship of a quantity with the main quantities of the system, in which the proportionality coefficient is equal to one. The dimension of a quantity is the product of the basic quantities raised to the appropriate powers.
A quantitative assessment of a specific physical quantity, expressed as a certain number of units of a given quantity, is called the value of a physical quantity. An abstract number included in the value of a physical quantity is called a numerical value, for example, 1 m, 5 g, 10 A, etc. There is a fundamental difference between the value and the size of a quantity. The size of a quantity really exists, whether we know it or not. You can express the size of a quantity using any unit.
The true value of the PV (the true value of the quantity) is the value of the PV, which would ideally reflect the corresponding property of the object in qualitative and quantitative terms. For example, the speed of light in a vacuum, the density of distilled water at a temperature of 44 °C have a well-defined value - the ideal one, which we do not know.
Experimentally, the actual value of a physical quantity can be obtained.
The actual value of the PV (the actual value of the quantity) is the value of the PV found experimentally and so close to the true value that for this purpose it can be used instead of it.
The size of the PV, denoted by Q, does not depend on the choice of unit, but the numerical value depends entirely on the chosen unit. If the size of the quantity Q in the system of units of PV "1" is defined as where p | - numerical value of the PV size in the "1" system; \Qi\ is a PV unit in the same system, then in another system of PV units "2", in which it is not equal to \Q(\, the unchanged size of Q will be expressed by a different value:
So, for example, the mass of the same loaf of bread can be 1 kg or 2.5 pounds, or the diameter of the pipe is 20 "or 50.8 cm.
Since the dimension of the PV is an expression that reflects the connection with the main quantities of the system, in which the proportionality coefficient is equal to 1, then the dimension is equal to the product of the main PV raised to the appropriate power.
In the general case, the dimension formula for PV units has the form where [Q] is the dimension of the derived unit; K is some constant number; [A], [I] and [C] - the dimension of the basic units;
a, P, y are positive or negative integers, including 0.
For K = 1, derived units are defined as follows:
If in a system length L, mass M and time T are accepted as basic units, it is denoted L, M, T. In this system, the dimension of the derived unit Q has the following form:
Systems of units whose derived units are formed according to the above formula are called consistent, or coherent.
The concept of dimension is widely used in physics, engineering, and metrological practice when checking the correctness of complex calculation formulas and elucidating the relationship between PV.
In practice, it is often necessary to use dimensionless quantities.
A dimensionless PV is a quantity whose dimension includes the main quantities to the power equal to 0. However, it should be understood that quantities that are dimensionless in one system of units may have a dimension in another system. For example, the absolute permittivity in an electrostatic system is dimensionless, while in an electromagnetic system its dimension is L~2T 2, and in the L M T I system its dimension is L-3 M - "T 4P.
Units of one or another physical quantity, as a rule, are associated with measures. The size of the unit of the measured physical quantity is assumed to be equal to the size of the quantity reproduced by the measure. However, in practice, one unit turns out to be inconvenient for measuring large and small sizes of a given quantity.
Therefore, several units are used, which are in multiple and submultiple ratios to each other.
A multiple of a PV unit is a unit that is an integer number of times greater than the base or derived unit.
A fractional PV unit is a unit that is an integer number of times smaller than the main or derived unit.
Multiple and submultiple units of PV are formed due to the corresponding prefixes to the basic units. These prefixes are given in Table 1.1.
Units of magnitude began to appear from the moment when a person had the need to express something quantitatively. Initially, the units of physical quantities were chosen arbitrarily, without any connection with each other, which created significant difficulties.
SI prefixes and multipliers for the formation of decimal multiples Multiplier In connection with this, the term "unit of physical quantity" was introduced.
The unit of the main PV (unit of quantity) is a physical quantity, which, by definition, is assigned a numerical value equal to 1. Units of the same PV can differ in size in different systems. For example, meter, foot and inch, being units of length, have different sizes:
With the development of technology and international relations, the difficulties in using the results of measurements expressed in different units increased and hindered further scientific and technological progress. The need arose to create a unified system of units of physical quantities. The system of PV units is understood as a set of basic PV units selected independently of each other and derived PV units, which are obtained from the basic ones on the basis of physical dependencies.
If the system of units of physical quantities does not have its own name, it is usually designated by its basic units, for example, LMT.
Derivative PV (derivative value) - PV included in the system and determined through the main quantities of this system according to known physical dependencies. For example, the speed in the system of quantities L M T is determined in the general case by the equation where v is the speed; / - distance; t - time.
For the first time, the concept of a system of units was introduced by the German scientist K. Gauss, who proposed the principle of its construction. According to this principle, the basic physical quantities and their units are first established. The units of these physical quantities are called basic, because they are the basis for constructing the entire system of units of other quantities.
Initially, a system of units was created based on three units: length - mass - time (centimeter - gram - second (CGS).
Let us consider the most widespread throughout the world and accepted in our country, the International System of Units SI, which contains seven basic units and two additional ones. The main FI units of this system are given in Table 1. 1.2.
Physical quantity Dimension Name Designation Mass current temperature Additional PV are:
Plane angle expressed in radians; radian (rad, rad), equal to the angle between two radii of a circle, the length of the arc between which is equal to the radius;
The solid angle, expressed in steradians, steradian (cp, sr), equal to the solid angle with the vertex at the center of the sphere, cutting out on the surface of the sphere an area equal to the area of a square with a side equal to the radius of the sphere.
The derived units of the SI system are formed using the simplest equations of connection between quantities and without any coefficient, since this system is coherent and ^=1. In this system, the dimension of the PV derivative [Q] is generally defined as follows:
where [I] - unit of length, m; [M] - unit of mass, kg; [T] - unit of time, s; [ /] - unit of current strength, A; [Q] - unit of thermodynamic temperature, K; [U] - unit of luminous intensity, cd; [N] - unit of quantity of substance, mol; a, (3, y, 8, e, co, X - positive or negative integers, including 0.
For example, the unit of speed in the SI system would look like this:
Since the written expression for the dimension of the derivative of the FW in the SI system coincides with the relation between the derivative of the FW and the units of the basic FW, it is more convenient to use the expression for the dimensions, i.e.
Similarly, the frequency of the periodic process F - T ~ 1 (Hz);
strength - LMT 2; density - _3M; energy - L2M T~2.
In a similar way, any derivative of the SI PV can be obtained.
This system was introduced in our country on January 1, 1982. GOST 8.417 - 2002 is currently in force, which defines the basic units of the SI system.
The meter is equal to 1650763.73 wavelengths in the vacuum of radiation corresponding to the transition between the 2p o and 5d5 levels of the crypton-86 atom.
The kilogram is equal to the mass of the international prototype of the kilogram.
A second is equal to 9,192,631,770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.
The ampere is equal to the strength of the unchanging current, which, when passing through two parallel rectilinear conductors of infinite length and negligible circular cross-sectional area, located in vacuum at a distance of 1 m from each other, would cause on each section of the conductor 1 m long interaction force equal to 2-10-7 N.
Kelvin is equal to 1/273.16 of the thermodynamic temperature of the triple point of water. (The temperature of the triple point of water is the temperature of the equilibrium point of water in the solid (ice), liquid and gaseous (steam) phases 0.01 K or 0.01 ° C above the melting point of ice).
The use of the Celsius scale (C) is allowed. The temperature in °C is denoted by the symbol t:
where T0 is 273.15 K.
Then t = 0 at T = 273.15.
A mole is equal to the amount of substance of a system containing as many structural elements as there are atoms in carbon de-12 weighing 0.012 kg.
The candela is equal to the intensity of light in a given direction of a source emitting monochromatic radiation with a frequency of 540 101 Hz, the energy intensity of which in this direction is 1/683 W/sr.
In addition to the system units of the SI system, in our country the use of some non-system units that are convenient for practice and traditionally used for measurement is legalized:
pressure - atmosphere (9.8 N / cm 2), bar, mm of mercury;
length - inch (25.4 mm), angstrom (10~sh m);
power - kilowatt-hour;
time - hour (3 600 s), etc.
In addition, logarithmic PVs are used - the logarithm (decimal or natural) of the dimensionless ratio of the PVs of the same name. Logarithmic PV is used to express sound pressure, amplification, attenuation. The unit of the logarithmic PV - bel (B) - is determined by the formula where P2 and P\ are energy quantities of the same name: power, energy.
For "power" quantities (voltage, current, pressure, field strength), the bel is determined by the formula A fractional unit of a bel is a decibel (dB):
Relative PVs, dimensionless ratios of two PVs of the same name, have received wide application. They are expressed in percent (%), dimensionless units.
In table. 1.3 and 1.4 are examples of derived SI units, the names of which are formed from the names of basic and additional units and have special names.
There are certain rules for writing unit symbols. When writing the designations of derived units of circulation, Table 1. Examples of SI derived units, the names of which are formed from the names of basic and additional units Derivative SI units with special names electric charge) voltage, electric potential, electric potential difference, electromotive force capacitance, filament induction resistance, magnetic flux, mutual inductance dots mi, standing on the middle line as a sign of multiplication "...". For example: N m (read "newton meter"), A - m 2 (ampere square meter), N - s / m 2 (newton second per square meter). The most common expression is in the form of a product of unit designations raised to the appropriate power, for example, m2-C "".
When the name corresponds to the product of units with multiple or submultiple prefixes and, it is recommended to attach the prefix to the name of the first unit included in the product. For example, 103 units of moment of force - new ton-meters should be called "kilone ton-meter", and not "new ton-kilometer". This is written as follows: kN m, not N km.
1. What is a physical quantity?
2. Why are quantities called physical?
3. What is meant by the size of the PV?
4. What does the true and actual value of PV mean?
5. What does dimensionless PV mean?
6. How does a multiple unit of PV value differ from a fractional one?
7. Indicate the correct answer to the following questions:
The SI unit of volume is:
1 liter; 2) gallon; 3) barrel; 4) cubic meter; 5) ounce;
The SI unit for temperature is:
1) degrees Fahrenheit; 2) degree Celsius; 3) Kelvin, 4) degree Rankine;
The SI unit of mass is:
1 ton; 2) carat; 3) kilogram; 4) pound; 5) ounce, 8. Without looking at the material covered, write in the column the names of the main physical quantities of the International System of Units SI, their names and symbols, 9. Name the known non-systemic units of physical quantities that are legalized and widely used in our country, 10 Try using Table 1.1 to assign prefixes to the basic and derived units of physical quantities and remember the most common in power engineering for measuring electrical and magnetic quantities, 1.3. Reproduction and transmission of dimensions As already mentioned, metrology is a science that is primarily concerned with measurements.
Measurement - finding the value of PV empirically with the help of special technical means.
Measurement includes various operations, after completion of which a certain result is obtained, which is the result of measurement (direct measurements) or the initial data for obtaining the result of observation (indirect measurements). Measurement includes observation.
Observation during measurement - an experimental operation performed in the course of measurements, as a result of which one value is obtained from a group of quantity values that are subject to joint processing to obtain a measurement result.
to use, it is necessary to ensure the uniformity of measurements.
The unity of measurements is such a state of measurements in which the measurement results are expressed in legal units, and their error is known with a given probability. It was also pointed out that measurement is the determination of the value of the PV by experience using special technical means - measuring instruments (SI). PV scale, reproduction, storage and transmission of PV units, PV Scale - a sequence of values assigned in accordance with the rules adopted by agreement, sequences of the same PV of various sizes (for example, the scale of a medical thermometer or scales).
Reproduction, storage and transmission of the sizes of PV units is carried out using standards. The highest link in the chain of transferring the sizes of PV units are standards, primary standards and copy standards.
The primary eta, yun is a standard that ensures the reproduction of the unit with the highest accuracy in the country (compared to other standards of the same unit).
Secondary standard - a standard whose value is set according to the primary standard.
A special standard is a standard that ensures the reproduction of a unit under special conditions and replaces the primary standard for these conditions.
State standard - a primary or special standard, officially approved as the initial al I of the country.
The standard-witness is a secondary standard designed to check the safety of the state standard and to replace it in case of damage or loss.
Standard-copy - a secondary standard designed to transfer the sizes of units to working standards.
Comparison standard - a secondary standard used to compare standards that, for one reason or another, cannot be directly compared with each other.
Working standard - the standard used to convey the size of the unit to the working SI.
Unit standard - a measuring instrument (or a set of measuring instruments) that provides reproduction and (or) storage of a unit in order to transfer its size to measuring instruments lower in the verification scheme, made according to a special specification and officially approved in the prescribed manner as a standard.
Reference installation - a measuring installation included in the SI complex, approved as a standard.
The main purpose of the standards is to provide the material and technical base for the reproduction and storage of PV units. They are systematized by reproducible units:
The basic units of the FI of the International SI system must be reproduced centrally with the help of State Standards;
Additional, derivative, and, if necessary, outside the system units of PV, based on technical and economic feasibility, are reproduced in one of two ways:
1) centrally with the help of a single State standard for the whole country;
2) decentralized through indirect measurements performed in the bodies of the metrological service using working standards.
Most of the most important derived units of the International System of Units SI are reproduced centrally:
newton - force (1 N = 1 kg - m s ~ 2);
joule - energy, work (1 J = 1 N m);
pascal - pressure (1 Pa = 1 N m~2);
ohm - electrical resistance;
volt is electrical voltage.
Units are reproduced in a decentralized manner, the size of which cannot be conveyed by direct comparison with a standard (for example, a unit of area) or if the verification of measures by indirect measurements is simpler than comparison with a standard and provides the necessary accuracy (for example, a unit of capacity and volume). At the same time, verification facilities of the highest accuracy are created.
State standards are stored in the relevant metrological institutes of the Russian Federation. According to the current decision of the State Standard of the Russian Federation, they are allowed to be stored and used in the bodies of departmental metrological services.
In addition to national standards of PV units, there are international standards stored in the International Bureau of Weights and Measures. Under the auspices of the International Bureau of Weights and Measures, a systematic international comparison of national standards of the largest metrological laboratories with international standards and among themselves is carried out. So, for example, the et & ton of the meter and the kilogram are compared once every 25 years, the standards of electrical voltage, resistance and light - once every 3 years.
Most of the standards are complex and very expensive physical installations that require the highest qualifications for their maintenance and the use of scientists to ensure their operation, improvement and storage.
Consider examples of some state standards.
Until 1960, the following meter standard acted as a standard of length. The meter was defined as the distance at 0°C between the axes of two adjacent strokes, marked on a platinum-iridium bar kept at the International Bureau of Measures and Weights, provided that this ruler is at normal pressure and supported by two rollers with a diameter of not less than 1 cm, located symmetrically in one longitudinal plane at a distance of 571 mm from one another.
The requirement for increased accuracy (a platinum-iridium bar does not allow reproducing a meter with an error of less than 0.1 μm), as well as the feasibility of establishing a natural and non-dimensional standard, led to the creation in 1960 of a new standard that is still valid meter, the accuracy of which is an order of magnitude higher than the old one.
In the new standard, the nonmeter is defined as a length equal to 1,650,763.73 vacuum wavelengths of radiation corresponding to the transition between the 2p C and 5d5 levels of the krypton-86 atom. The physical principle of the standard is to determine the radiation of light energy during the transition of an atom from one energy level to another.
The place of storage of the meter standard is VY IIM im. D. I. Mendeleev.
The standard deviation (RMS) of the reproduction of a unit of meter does not exceed 5 10 ~ 9 m.
The standard is constantly being improved in order to increase the accuracy, stability, and reliability, taking into account the latest achievements in physics.
The state primary standard of the RF mass (kilogram) is stored in the VN I M im. D. I. Mendeleev. It ensures the reproduction of a mass unit of 1 kg with an RMS of no more than 3 10~8 kg. The composition of the state primary standard of the kilogram includes:
A copy of the international prototype of the kilogram - platinum-iridium prototype No. 12, which is a weight in the form of a cylinder with rounded ribs with a diameter of 39 mm and a height of 39 mm;
Reference scales No. 1 and No. 2 for 1 kg with remote control for transferring the size of a mass unit from prototype No. to copy standards and from copy standards to working standards.
The standard unit of electric current strength is stored in VN AND IM them. D. I. Mendeleev. It consists of a current scale and apparatus for transmitting the size of a unit of current strength, which includes an electrical resistance coil, which received the resistance value from the primary standard of the unit of electrical resistance - ohm.
The standard deviation of the reproduction error does not exceed 4-10~6, the non-excluded systematic error does not exceed 8 10~6.
The temperature unit standard is a very complex setup. Temperature measurement in the range of 0.01 ... 0.8 K is carried out on the temperature scale of the magnetic susceptibility thermometer TSh TM V. In the range of 0.8 ... 1.5 K, the helium-3 (3He) scale is used, based on the dependence pressure of saturated vapors of helium-3 on temperature. In the range 1.5...4.2 K, the helium-4 (4H) scale is used, based on the same principle.
In the range of 4.2 ... 13.81 K, the temperature is measured on the scale of a germanium resistance thermometer T Sh GTS. In the range of 13.81 ... 6300 K, the international practical scale M P TSh -68 is used, based on a number of reproducible equilibrium states of various substances.
The transfer of unit sizes from the primary standard to working measures and measuring instruments is carried out with the help of bit standards.
A discharge standard is a measure, a measuring transducer or a measuring device that serves to verify other measuring instruments against them and is approved by the bodies of the State Metrological Service.
The transfer of dimensions from the corresponding standard to the working measuring instruments (RSI) is carried out according to the verification scheme.
A verification scheme is a duly approved document that establishes the means, methods and accuracy of transferring the size of a unit from a standard to a working SI.
The scheme for transferring sizes (metrological chain) from standards to working SI (primary standard - standard copy - bit standards - "working SI") is shown in fig. 1.2.
There is a subordination between bit standards:
standards of the first category are verified directly against copy standards; standards of the second category - according to the standards of the 1st category, yes, etc.
Separate working measuring instruments of the highest accuracy can be verified by copy standards, the highest accuracy - by standards of the 1st category.
Discharge standards are located in the metrological institutes of the State Metrological Service (MS), as well as in the county. 1.2. Scheme for transferring the dimensions of fixed laboratories of industry-specific MS, which, in the prescribed manner, have been granted the right to calibrate SI.
SI as a discharge standard are approved by the State Ministry of International Relations. To ensure the correct transmission of PV dimensions in all links of the metrological chain, a certain order must be established. This order is given in the verification charts.
The regulation on verification schemes is established by GOST 8.061 - “GSI. Verification schemes. Content and construction.
There are State verification schemes and local (individual regional bodies of the State MS or departmental MS). Verification schemes contain a text part and the necessary drawings and diagrams.
Strict adherence to verification schemes and timely verification of discharge standards are necessary conditions for transferring reliable sizes of units of physical quantities to working measuring instruments.
Directly to perform measurements in science and technology, working measuring instruments are used.
The working means of measurement is C I, used for measurements not related to the transfer of dimensions.
1. What is the standard unit of physical quantity?
2. What is the main purpose of standards?
3. On what principles is the standard unit of length based?
4. What is a verification scheme?
From the point of view of information theory, measurement is a process aimed at reducing the entropy of the measured object. Entropy is a measure of the uncertainty of our knowledge about the object of measurement.
In the process of measurement, we reduce the entropy of the object, i.e.
get additional information about the object.
Measurement information is information about the values of the measured PV.
This information is called measurement information, because it is obtained as a result of measurements. Thus, measurement is finding the value of the PV by experience, which consists in comparing the measured PV with its unit using special technical means, which are often called measuring instruments.
The methods and technical means used in the measurements are not ideal, and the experimenter's organs of perception cannot perfectly perceive the readings of the instruments. Therefore, after the completion of the measurement process, there remains some uncertainty in our knowledge about the object of measurement, i.e., it is impossible to obtain the true value of the PV. The residual uncertainty of our knowledge about the measured object can be characterized by various measures of uncertainty. In metrological practice, entropy is practically not used (with the exception of analytical measurements). In the theory of measurements, the measure of uncertainty in the result of measurements is the error in the result of observations.
The error of the measurement result, or measurement error, is understood as the deviation of the measurement result from the true value of the measured physical quantity.
It is written as follows:
where X tm - measurement result; X - true value of PV.
However, since the true value of the PV remains unknown, the measurement error is also unknown. Therefore, in practice, one deals with approximate values of the error or with their so-called estimates. Instead of the true value of the FV, its actual value is substituted into the formula for estimating the error. The actual value of the PV is understood as its value, obtained empirically and so close to the true value that for this purpose it can be used instead of it.
Thus, the formula for estimating the error has the following form:
where XL is the actual value of the PV.
Thus, the smaller the error, the more accurate the measurements.
Measurement accuracy - the quality of measurements, reflecting the closeness of their results to the true value of the measured value. Numerically, it is the inverse of the measurement error, for example, if the measurement error is 0.0001, then the accuracy is 10,000.
What are the main reasons for the error?
Four main groups of measurement errors can be distinguished:
1) errors due to measurement procedures (measurement method error);
2) error of measuring instruments;
3) the error of the sense organs of observers (personal errors);
4) errors due to the influence of measurement conditions.
All these errors give the total measurement error.
In metrology, it is customary to subdivide the total measurement error into two components: random and systematic errors.
These components are different in their physical essence and manifestation.
Random measurement error - a component of the error of measurement results, changing randomly (in sign and value) in repeated observations carried out with the same thoroughness of the same unchanged (determined) PV.
The random component of the total error characterizes such quality of measurements as their accuracy. The random error of the measurement result is characterized by the so-called dispersion D. It is expressed by the square of the units of the measured PV.
Since this is inconvenient, in practice, the random error is usually characterized by the so-called standard deviation. Mathematically, the standard deviation is expressed as the square root of the variance:
The standard deviation of the measurement result characterizes the dispersion of the measurement results. This can be explained as follows. If you aim your rifle at a point, fix it rigidly and fire a few shots, then not all bullets will hit that point. They will be located near the aiming point. The degree of their spread from the specified point will be characterized by the standard deviation.
Systematic measurement error - a component of the error of the measurement result, which remains constant or regularly changes during repeated observations of the same unchanged PV. This component of the total error characterizes such quality of measurements as their correctness.
In the general case, these two components are always present in the measurement results. In practice, it often happens that one of them significantly exceeds the other. In these cases, the smaller component is neglected. For example, in measurements carried out with a ruler or tape measure, as a rule, the random component of the error predominates, while the systematic component is small and is neglected. The random component in this case is explained by the following main reasons: inaccuracy (skew) of the tape measure (ruler), inaccuracy of setting the start from the count, change in the observation angle, eye fatigue, change in illumination.
A systematic error arises due to the imperfection of the method of performing measurements, errors in measuring instruments, inaccurate knowledge of the mathematical model of measurements, the influence of conditions, errors in calibration and verification of measuring instruments, and personal reasons.
Since random errors in measurement results are random variables, their processing is based on the methods of probability theory and mathematical statistics.
Random error characterizes such a quality as the accuracy of measurements, and systematic error characterizes the correctness of measurements.
According to its expression, the measurement error can be absolute and relative.
Absolute error - an error expressed in units of the measured value. For example, the error in measuring a mass of 5 kg is 0.0001 kg. It is marked D.
Relative error is a dimensionless quantity, determined by the ratio of the absolute error to the actual value of the measured PV, it can be expressed as a percentage (%). For example, the relative error in measuring the mass of 5 kg is Q'QQQl _ 0.00002 or 0.002%. Sometimes the ratio of the absolute error to the maximum value of the PV that can be measured by the given MI (the upper limit of the instrument scale) is taken. In this case, the relative error is called reduced.
The relative error is designated 8 and is defined as follows:
where D is the absolute error of the measurement result; Xs - actual value of PV; Xtm - the result of measuring the EF.
Since Xs \u003d Xtm (or very little differs from it), then in practice it is usually accepted. In addition to random and systematic measurement errors, there is a so-called gross measurement error. And yes, in the literature, this error is called a miss. The gross error of a measurement result is an error that is significantly greater than expected.
As already noted, in the general case, both components of the total measurement error manifest themselves simultaneously:
random and systematic, therefore where: D - total measurement error; D is the random component of the measurement error; 0 is the systematic component of the measurement error.
Types of measurements are usually classified according to the following criteria:
accuracy characteristic - equally accurate e, unequal (equally scattered, unequally scattered e);
number of measurements - single, multiple;
relation to the change in the measured value - static, dynamic;
metrological purpose - metrological, technical;
measurement result expression - absolute, relative;
general methods for obtaining measurement results - direct, indirect, joint, cumulative.
Equivalent measurements - a series of measurements of any value, made with the same accuracy of SI and under the same conditions.
Unequal measurements - a series of measurements of some value, performed by several measuring instruments with different accuracy and (or) under different conditions.
Single measurement - measurement performed once.
Multiple measurements - measurements of the same PV size, the result of which is obtained from several consecutive observations, i.e. consisting of a number of single measurements.
Direct measurement - measurement of the PV, carried out by a direct method, in which the desired value of the PV is obtained directly from the experimental data. Direct measurement is performed by experimental comparison of the measured PV with a measure of this value or by reading the SI readings on a scale or digital device.
For example, measuring length, height with a ruler, voltage with a voltmeter, mass with a scale.
Indirect measurement - a measurement carried out by an indirect method, in which the desired value of the CF is found on the basis of the result of a direct measurement of another FC, functionally related to the desired value by a known relationship between this FC and the value obtained by direct measurement. For example:
determination of area, volume by measuring length, width, height; electric power - by the method of measuring current and voltage, etc.
Cumulative measurements are simultaneous measurements of several quantities of the same name, in which the desired values of the quantities are determined by solving a system of equations obtained by measuring various combinations of these quantities.
EXAMPLE: The value of the mass of individual weights of the set is determined by the known value of the mass of one of the weights and by the results of measurements (comparisons) of the masses of various combinations of weights.
There are weights with masses m and mb/u3:
where L/] 2 is the mass of the weights W and m2", M, 2 3 is the mass of the weights m and m2 tg.
This is often the way to improve the accuracy of measurement results.
Joint measurements are simultaneous measurements of two or more non-identical physical quantities to determine the relationship between them.
As already mentioned, measurement is the process of finding the values of a physical quantity. Thus, a physical quantity is an object of measurement. In addition, it should be borne in mind that a physical quantity is such a quantity, the size of which can be determined by physical methods. That is why the quantity is called physical.
The value of a physical quantity is determined using measuring instruments by a certain method. The measurement method is understood as a set of methods for using the principles and means of measurement. The following measurement methods are distinguished:
direct assessment method - a method in which the value of a quantity is determined directly by the reporting device of the measuring device (length measurement using a ruler, mass - using spring scales, pressure - using a pressure gauge, etc.);
method of comparison with a measure - a method of measurement in which the measured value is compared with the value reproduced by the measure (measuring the gap between parts using a feeler gauge, measuring mass on a balance scale using weights, measuring length with the help of gauges, etc. );
opposition method - a method of comparison with a measure, in which the measured value and the value reproduced by the measure simultaneously affect the comparison device, with the help of which the ratio between these quantities is established (measurement of mass on equal-arm balances with the placement of the measured mass and weights balancing it on two scales);
differential method - a method of comparison with a measure, in which the measuring instrument is affected by the difference between the measured and known values, reproduced by the measure (length measurement by comparison with an exemplary measure on a comparator - a comparison tool designed to compare measures of homogeneous quantities);
zero method - a method of comparison with a measure, in which the resulting effect of the impact of quantities on the comparison device is brought to zero (measurement of electrical resistance by a bridge with its full balancing);
substitution method - a method of comparison with a measure in which the measured value is mixed with a known value reproducible by the measure (weighing with alternate placement of the measured mass and weights on the same scale pan);
coincidence method - a method of comparison with a measure in which the difference between the measured value and the value reproduced by the measure is measured using coincidence from scale marks or periodic signals (length measurement using a compass caliper with a vernier when observing the coincidence of marks on the scales w tangent caliper and vernier; measurement of rotational speed using a stroboscope, when the position of any mark on a rotating object is aligned with a mark on the non-rotating part of a certain flash frequency of the stroboscope).
In addition to the noted methods, there are contact and non-contact measurement methods.
The contact measurement method is a measurement method based on the fact that the sensitive element of the device is brought into contact with the measurement object. For example, measuring the dimensions of a hole with a caliper or an indicator inside gauge.
A non-contact measurement method is a measurement method based on the fact that the sensitive element of the measuring instrument is not brought into contact with the measurement object. For example, measuring the distance to an object using a radar, measuring thread parameters using an instrumental microscope.
So, we have dealt (we hope) with some of the provisions of metrology associated with units of physical quantities, systems of units of physical quantities, groups of errors in the result of measurements, and, finally, with the types and methods of measurements.
We have come to one of the most important sections of the science of measurement - the processing of measurement results. In fact, the result of the measurement and its error depend on what method of measurement we have chosen, what we have measured, how we have measured. But without processing these results, we will not be able to determine the numerical value of the measured value, to draw any specific conclusion.
By and large, the processing of measurement results is a responsible and sometimes difficult stage in preparing an answer to the question about the true value of the measured parameter (physical quantity). This includes the determination of the mean value of the measured value and its dispersion, and the determination of confidence intervals of errors, the determination and exclusion of gross errors, the assessment and analysis of systematic errors, etc. More details on these issues can be found in other literature. Here, we consider only the first steps performed in processing the results of equally accurate measurements, which obey the normal distribution law.
As has already been pointed out, it is impossible in principle to determine the true value of a physical quantity from the results of its measurement. Based on the measurement results, an estimate of this true value (its average value) and q and the range within which the desired value is located with the accepted confidence probability can be obtained. In other words, if the accepted confidence probability is equal to 0.95, then the true value of the measured physical quantity with a probability of 95% is within a certain interval of the results of all measurements.
The final task of processing the results of any measurements is to obtain an estimate of the true value of the measured physical quantity, denoted by Q, and the range of values within which this estimate is located with the accepted confidence level.
For equally accurate (evenly scattered) measurement results, this estimate is the arithmetic mean of the measured quantity from n single results:
where n is the number of single measurements in a row; Xi - measurement results.
To determine the range (confidence interval) of change in the average value of the measured physical quantity, it is necessary to know the law of its distribution and the law of distribution of the error of measurement results. In metrological practice, the following laws of distribution of measurement results and their errors are usually used: normal, uniform, triangular, and trapezoidal.
Let us consider the case when the dispersion of the measurement results obeys the normal distribution law, and the measurement results are equally accurate.
At the first stage of processing the measurement results, the presence of gross errors (misses) is assessed. For this, the root mean square error of the results of single measurements in a series of measurements (S K P) is determined. Instead of the term S K P, the term “standard deviation”, which is denoted by the symbol S, is widely used in practice. errors, S K P and RMS are the same estimate of the scatter of the results of single measurements.
To assess the presence of gross errors, the determination of the confidence limits of the measurement result error is used.
In the case of a normal distribution law, they are calculated as where t is a coefficient depending on the confidence probability P and the number of measurements (selected from the tables).
If among the measurement results there are those whose values go beyond the confidence limits, i.e., more or less than the average value of x by 35, then they are gross errors and are excluded from further consideration.
The accuracy of the results of observations and subsequent calculations during data processing must be consistent with the required accuracy of the measurement results. The error of the measurement results should be expressed in no more than two significant figures.
When processing the results of observations, the rules of approximate calculations should be used, and rounding should be performed according to the following rules.
1. The measurement result should be rounded so that it ends with a figure of the same order as the error. If the value of the measurement result ends in zeros, then zero is discarded to the bit that corresponds to the bit of the error.
For example: error D = ±0.0005 m.
After the calculations, the following measurement results were obtained:
2. If the first of the zero-replaced or discarded digits (from left to right) is less than 5, then the remaining digits are not changed.
For example: D = 0.06; X - 2.3641 = 2.36.
3. If the first of the zero-replaced or discarded digits is equal to 5, and it is not followed by any digits or zeros, then rounding is performed to the nearest even number, i.e. the last remaining even digit or zero is left unchanged, the odd one is increased by /:
For example: D = ±0.25;
4. If the first of the zero-replaced or discarded digits is greater than or equal to 5, but followed by a non-zero digit, then the last remaining digit is increased by 1.
For example: D = ±1 2; X x \u003d 236.51 \u003d 237.
Further analysis and processing of the obtained results is carried out in accordance with GOST 8.207 - 80 GSI “Direct measurements with multiple observations. Methods for Processing the Results of Observations”.
Consider an example of the initial processing of the results of single measurements of the diameter of the shaft neck (Table 1.5), performed with a micrometer under the same conditions.
1. Arrange the obtained results in a monotonically increasing series:
Xi;...10.03; 10.05; 10.07; 10.08; 10.09; 10.10; 10.12; 10.13; 10.16;
2. Determine the arithmetic mean of the measurement results:
3. Let us determine the root mean square error of the measurement results in the resulting series:
4. Determine the interval in which the measurement results will be located without gross errors:
5. Determine the presence of blunders: in our particular example, the measurement results do not have blunders and, consequently, all of them are accepted for further processing.
Measurement number 10.08 10.09 10.03 10.10 10.16 10.13 10.05 10.30 10.07 10 Neck diameter, mm If 10.341 mm and less than 9.885 mm, then they would have to be excluded and the X and S values should be determined again.
1. What measurement methods are used in industry?
2. What is the purpose of processing the measurement results?
3. How is the arithmetic mean of the measured value determined?
4. How is the root mean square error of the results of single measurements determined?
5. What is a corrected series of measurements?
6. How many significant digits should the measurement error contain?
7. What are the rules for rounding calculation results?
8. Determine the presence and exclude from the results of equally accurate measurements of the voltage in the network, performed by a voltmeter, gross errors (measurement results are presented in volts): 12.28; 12.38; 12.25:
12,75; 12,40; 12,35; 12,33; 12,21; 12,15;12,24; 12,71; 12,30; 12,60.
9. Round off the measurement results and write it down, taking into account the error:
1.5. Measuring and control instruments Classification of measuring and control instruments. A person, practically both in everyday life and in work activities, makes various measurements all the time, often without even thinking about it. He measures his every step with the nature of the road, feels warm or cold, the level of illumination, using a centimeter, measures the volume of his chest to choose clothes etc. But, of course, only with the help of special tools can he obtain reliable data on those or other parameters that he needs.
The classification of measuring and control means according to the type of controlled physical quantities includes the following main quantities; weight values, geometric values, mechani cal values, pres sures, quantity, flow rate, substance level, time and frequency, physical chemical composition of matter, thermal quantities, electrical and magnetic quantities, radiotechnical quantities, optical radiation, ionizing radiation, acoustic quantities.
Each type of controlled physical quantities, in turn, can be subdivided into types of controlled quantities.
So, for electrical and magnetic quantities, the main types of measuring and control instruments can be distinguished: voltage, current, power, phase shifts, resistance, frequency, magnetic field strength, etc.
Universal measuring instruments allow measurements of many parameters. For example, a multimeter widely used in practice makes it possible to measure direct and alternating voltages, current strength, and resistance values. In mass production, the worker at his workplace often has to control only one or a limited number of parameters. In this case, it is more convenient for him to use one-dimensional measuring instruments, the reading of the measurement results from which is faster and greater accuracy can be obtained. So, for example, when setting up voltage stabilizers, it is enough to have two devices independent of each other: a voltmeter to control the output voltage and an ammeter to measure the load current in the operating range of the stabilizer.
The automation of the production process has led to the fact that automatic controls have been increasingly used. In many cases, they provide information only when the measured parameter deviates from the specified values. Automatic controls are classified according to the number of parameters to be checked, the degree of automation, the method of converting the measuring pulse, the impact on the technological process, and the use of a computer.
The latter are increasingly included in the composition of various technical devices; they make it possible to detect malfunctions that occur during operation, issue them at the request of the operating personnel, and even indicate methods for eliminating the malfunctions that have occurred, detected using various measuring devices that are part of the technical equipment itself. devices. So, when conducting a periodic technical inspection of a car (and this is provided for by the relevant rules), instead of directly connecting measuring instruments to various units, it is enough to connect only one measuring, and actually fixing, device in the form of a laptop to which the car computer ( and there may even be several of them) will give all the information not only about the current state of the vehicle equipment, but also the statistics of the malfunctions that have occurred over the past few months. It should be noted that due to the fact that many measuring devices that are part of the vehicle equipment (or other technical devices) work for the printer, it issues recommendations: remove, discard, replace with a new one. Computers in the form of microprocessors are directly included in various measuring instruments, for example, oscilloscopes, signal spectrum analyzers, and nonlinear distortion meters. They process the measured information, remember it, and give it to the operator in a convenient form not only during measurements, but also after some time at the request of the experimenter.
It is possible to classify according to the method of converting the measurement pulse; mechanical methods, pneumatic, hydraulic, electrical, optical acoustic, etc.
Practically in each of the listed methods it is possible to carry out additional classification. For example, electrical methods may use DC or AC voltage signals, low frequency, high frequency, sub-low frequency, and so on. In medicine, fluorographic and fluoroscopic methods of transformation are used. Or the recently appeared magnetic resonance imaging (computed tomography).
All this practically shows that it is actually not advisable to carry out a comprehensive classification according to some general principles. At the same time, due to the fact that in recent years, electronic and electrical methods, computer technology have been increasingly introduced into the process of measuring parameters of various types, it is necessary to pay more attention to this method.
Electrical measurement and control methods make it quite easy to memorize the results obtained, process them statistically, determine the mean value, dispersion, and predict subsequent measurement results.
And the use of electronics makes it possible to transmit measurement results via communication channels. For example, on modern cars, information about a decrease in tire pressure (and this is necessary to prevent emergency information) is transmitted to the driver via a radio channel. To do this, instead of a spool, a miniature pressure sensor with a radio transmitter is screwed onto the tire chamber nipple, which transmits information from a rotating wheel to a fixed antenna and then to the driver's instrument panel. With the help of radar on the latest types of cars, the distance to the front of the car is determined, and if it becomes too small, the brakes are automatically applied without the participation of the driver. In aviation, with the help of the so-called black boxes (in fact, they are bright orange so that they are visible), information is recorded on the flight mode, the operation of all the main devices of the aircraft, which makes it possible, in the event of a catastrophe, to find its cause and take measures to eliminate such situations in the future. Such devices, at the request of insurance companies, are beginning to be introduced in a number of countries and on cars. Radio channels for transmitting measurement information from launched satellites and ballistic missiles are widely used. This information is processed automatically (seconds play the role here) and in the event of a deviation from the given trajectory or an emergency, a command is transmitted from the ground to self-destruct the launched object.
Generalized block diagrams of measurement and control instruments.
To create and study measuring systems, individual measuring instruments, the so-called general block diagrams of measuring and control instruments are often used. These schemes depict individual elements of the measuring instrument in the form of symbolic blocks interconnected by signals characterizing physical quantities.
GOST 16263 - 70 defines the following general structural elements of measuring instruments: sensitive, converting elements, measuring circuit, measuring mechanism, reading device, scale, pointer, recording device (Fig. 1.3).
Almost all elements of the block diagram, except for the sensing element (in some cases, it too) operate on the principles of electrical engineering and electronics.
The sensitive element of the measuring instrument is the first transducer element, which is directly affected by the measured value. Only this element has the ability to capture changes in the measured value.
Structurally, sensitive elements are very diverse, some of them will be considered further when studying sensors. The main task of the sensitive element is to generate a signal of measuring information in a form convenient for its further processing. This signal can be purely mechanical, such as moving or turning. But the optimal is an electrical signal (voltage or, less often, current), which is subjected to convenient further processing. So, for example, when measuring pressure (liquid, gas), the sensitive element is a corrugated elastic membrane. 1.3. The generalized structural diagram of measuring instruments and control of the paradise is deformed under the influence of pressure, i.e., pressure is converted into linear displacement. And measuring the luminous flux with a photodiode directly converts the intensity of the luminous flux into voltage.
The conversion element of the measuring instrument converts the signal generated by the sensitive element into a form convenient for subsequent processing and transmission over a communication channel. Thus, the previously considered sensitive element for measuring pressure, at the output of which linear displacement requires the presence of a transducer element, for example, a potentiometric sensor, which makes it possible to convert linear displacement into a voltage proportional to displacement.
In some cases, it is necessary to apply several converters in series, the output of which will eventually be a signal that is convenient for use. In these cases, one speaks of the first, second, and other converters connected in series. In fact, such a serial circuit of converters is called the measuring circuit of the measuring instrument.
The indicator is necessary for issuing the obtained measurement information to the operator in a form convenient for perception. Depending on the nature of the signal coming to the indicator from the measuring circuit, the indicator can be made both with the help of mechanical or hydraulic elements (for example, a pressure gauge), and in the form (most often) of an electric voltmeter.
The information itself can be presented to the operator in analog or discrete (digital) form. In analog indicators, it is usually represented by a pointer moving along a scale with imprinted values of the measured value (the simplest example is an analogue clock) and much less often with a stationary pointer with a moving scale. Discrete digital indicators provide information in the form of decimal digits (the simplest example is a clock with digital indication). Digital indicators make it possible to obtain more accurate measurement results compared to analog ones, but when measuring rapidly changing values, the operator on the digital indicator sees the flashing of numbers, while on the analog device the movement of the arrow is clearly visible. So, for example, ended in failure to use digital speedometers on cars.
The results of measurements can, if necessary, be stored in the memory of the measuring device, which are usually microprocessors. In these cases, the operator can, after some time, retrieve the previous measurement results he needs from memory. So, for example, on all locomotives of railway transport there are special devices that record the speed of the train on different sections of the track. This information is delivered at the end stations and is processed to take action against speed violators on different sections of the road.
In some cases, it is necessary to transmit the measured information over a long distance. For example, tracking earth satellites by special centers located in different regions of the country. This information is promptly transmitted to the central point, where it is processed to control the movement of satellites.
To transfer information, depending on the distance, various communication channels can be used - electric cables, light guides, infrared channels (the simplest example is remote control of the TV using a remote control), radio channels. Analog information can be transmitted over short distances. For example, in a car, information about the oil pressure in the lubrication system is transmitted directly in the form of an analog signal via wires from the pressure sensor to the indicator. With relatively long communication channels, it is necessary to use the transmission of digital information. This is due to the fact that when transmitting an analog signal, its weakening is inevitable due to the voltage drop in the wires. But it turned out that it was impossible to transmit digital information in the decimal number system. It is impossible to set a specific voltage level for each digit, for example: digit 2 - 2 V, digit 3 - 3 V, etc. The only acceptable way turned out to be to use the so-called binary number system, in which there are only two digits: zero and one. They can establish the relationship zero - zero voltage, and unity - some other than zero. It doesn't matter what. It can be both 3 V and 10 V. In all cases, it will correspond to the unit of the binary system. By the way, any computer and portable calculators work in the same way in the binary system. Special circuits in them recode the decimal information entered using the keyboard into binary, and the results of the calculation from binary form into the decimal form familiar to us.
Although we often say that some information contains a large amount of information or there is practically no information here, we do not think about the fact that information can be given a well-defined mathematical interpretation. The concept of a quantitative measure of information was introduced by the American scientist C. Shannon, one of the founders of information theory:
where I is the amount of information received; pn is the probability for the information receiver of an event after receiving the information; p is the probability of the information receiver of the event before receiving and information.
The logarithm at base 2 can be calculated by the formula If the information is received without errors, which in principle can be in the communication line, then the probability of an event at the message receiver is equal to one. Then the formula for the quantitative assessment of information will take a simpler form:
As a unit of measure for the amount of information, a unit called a bit is adopted. For example, if with the help of devices it is established that there is voltage at the output of some device (and there are options: there is voltage or not) and the probabilities of these events are equally probable, i.e. p = 0.5, then the amount of information Determining the amount of information transmitted over a communication channel is important because any communication channel can transmit information at a certain rate, measured in bits/s.
According to a theorem called Shannon's theorem, for the correct transmission of a message (information), it is necessary that the rate of information transfer be greater than the performance of the information source. So, for example, the standard transmission rate of a television image in digital form (namely, this is how satellite television works and in the coming years terrestrial television will also switch to this method) is 27,500 kbps. It must be borne in mind that in some cases important information taken from the oscilloscope (signal shape, instrument scales, etc.) is transmitted through the television channel. Since communication channels, whatever they are, have quite definite values of the maximum information transfer rate, various methods of compressing the volume of information are used in information systems. For example, not all information can be transmitted, but only its change. To reduce the volume of information in some continuous process, one can limit oneself to preparing for the transmission of data about this process over a communication channel only at certain points in time, by carrying out a survey and obtaining so-called samples. Typically, the survey is carried out at regular intervals T - the survey period.
Restoration at the receiving end of the communication channel of a continuous function is carried out with the help of interpolation processing, which is usually carried out automatically. In a data transmission system using samples, a continuous signal source is converted into a sequence of pulses of different amplitudes with the help of an electronic key (modulator). These pulses enter the communication channel, and on the receiving side, a filter chosen in a certain way turns the sequence of pulses back into a continuous signal. The key also receives a signal from a special pulse generator, which opens the key at regular intervals T.
The possibility of restoring the original signal shape from samples was indicated in the early 1930s by Kotelnikov, who formulated the theorem that bears his name today.
If the spectrum of the function Dz) is limited, i.e.
where /max is the maximum frequency in the spectrum, and if the polling is carried out with a frequency / = 2/max, then the function /(/) can be exactly reconstructed from the samples.
Metrological characteristics of measuring and control instruments. The most important properties of measuring and control instruments are those on which the quality of the measurement information obtained with their help depends. The quality of measurements is characterized by accuracy, reliability, correctness, convergence and reproducibility of measurements, as well as the size of permissible errors.
Metrological characteristics (properties) of measuring and control instruments are those characteristics that are intended to assess the technical level and quality of a measuring instrument, to determine the measurement results and to estimate the characteristics of the instrumental component of the measurement error.
GOST 8.009 - 84 establishes a set of normalized metrological characteristics of measuring instruments, which is selected from among those given below.
Characteristics intended to determine the results of measurements (without correction):
transmitter conversion function;
the value of a single value or the value of a multivalued measure;
the scale division value of a measuring instrument or a multivalued measure;
type of output code, number of code bits.
Characteristics of errors of measuring instruments - characteristics of the systematic and random components of errors, variation of the output signal of a measuring instrument or characteristic of an error of measuring instruments.
Characteristics of the sensitivity of measuring instruments to influencing quantities - a function of influence or a change in the values of the metrological characteristics of measuring instruments caused by changes in influencing quantities within the established limits.
The dynamic characteristics of measuring instruments are divided into complete and partial. The former include: transient response, amplitude-phase and impulse responses, transfer function. Particular dynamic characteristics include: reaction time, damping factor, time constant, value of the resonant natural circular frequency.
Non-informative parameters of the output signal of measuring instruments - parameters of the output signal that are not used to transmit or indicate the value of the informative parameter of the input signal of the measuring transducer or are not the output value of the measure.
Let us consider in more detail the most common metrological indicators of measuring instruments, which are provided by certain design solutions of measuring instruments and their individual units.
The scale division value is the difference between the values of the quantities corresponding to two adjacent scale marks. For example, if the movement of the scale pointer from position I to position II (Fig. 1.4, a) corresponds to a change in value of 0.01 V, then the division value of this scale is 0.01 V. The division values are selected from the series 1, 2, 5, 10, 20, 50, 100, 200, 500. But most often multiple and fractional values from 1 to 2 are used, namely: 0.01;
0.02; 0.1; 0.2; one; 2; 10 etc. The division value of the scale is always indicated on the scale of the measuring instrument.
The scale division interval is the distance between the midpoints of two adjacent scale strokes (Fig. 1.4, b). In practice, based on the resolving power of the operator's eyes (visual acuity), taking into account the width of the strokes and the pointer, the minimum interval for dividing the scale is taken to be 1 mm, and the maximum - 2.5 mm. The most common spacing value is 1 mm.
The initial and final values of the scale are, respectively, the smallest and largest value of the measured value indicated on the scale, characterizing the capabilities of the scale of the measuring instrument and determining the range of indications.
One of the main characteristics of measuring instruments by the contact method is the measuring force that occurs in the contact zone of the measuring tip of the measuring instrument with the measured surface in the direction of the measurement line. It is necessary in order to ensure a stable circuit of the measuring circuit. Depending on the tolerance of the controlled product, the recommended values of the measuring force are in the range from 2.5 to 3.9 N. An important indicator of the measuring force is the difference in the measuring force - the difference in the measuring force at two positions of the pointer within the range of indications. The standard limits this value depending on the type of measuring instrument.
The property of a measuring instrument, which consists in its ability to respond to changes in the measured quantity, is called sensitivity. It is estimated by the ratio of the change in the position of the pointer relative to the scale (expressed in linear or angular units) to the corresponding change in the measured value.
The sensitivity threshold of a measuring instrument is a change in the measured value, causing the smallest change in its readings, detected with a reference method that is normal for this instrument. This characteristic is important when assessing small displacements.
Variation of indications - the largest experimentally determined difference between repeated indications and means of measurements corresponding to the same actual value of the quantity measured by it under constant external conditions. Usually, the variation of readings for measuring instruments is 10 ... 50% of the division value, it is determined by multiple caging of the tip of the measuring instrument.
The sensors are characterized by the following metrological characteristics:
Nominal static characteristic of transformation S f H „x). This normalized metrological characteristic is the calibration characteristic of the transducer;
Conversion coefficient - the ratio of the increment of the value of an electrical quantity to the increment of a non-electric quantity that caused it Kpr \u003d AS / AXtty limiting sensitivity - sensitivity threshold;
systematic component of the conversion error;
random component of the conversion error;
Dynamic conversion error - due to the fact that when measuring rapidly changing values, the inertia of the converter leads to a delay in its response to a change in the input value.
A special place in the metrological characteristics of measuring and control instruments is occupied by measurement errors, in particular, the errors of the measuring and control instruments themselves. In subsection 1. The main groups of measurement errors have already been considered, which are the result of a number of reasons that create a cumulative effect.
The measurement error is the deviation D of the measurement result Xtm from the actual value Xa of the measured value.
Then the error of the measuring instrument is the difference Dp between the instrument reading Xp and the actual value of the measured quantity:
The error of a measuring instrument is a component of the total measurement error, which in the general case includes, in addition to Dn, errors in setting measures, temperature fluctuations, errors caused by a violation of the primary setting of the measuring instrument, elastic deformations of the measurement object, due to the quality of the measured surface, and others.
Along with the terms "measurement error", "measuring instrument error", the concept of "measurement accuracy" is used, which reflects the closeness of its results to the true value of the measured quantity. High measurement accuracy corresponds to small measurement errors. Measurement errors are usually classified according to the reason for their occurrence and according to the type of errors.
Instrumental errors arise due to the insufficiently high quality of the elements of measuring and control instruments. These errors include errors in the manufacture and assembly of measuring instruments; errors due to friction in the SI mechanism, insufficient rigidity of its parts, etc. The instrumental error is individual for each SI.
The reason for the occurrence of methodological errors is the imperfection of the measurement method, i.e. what we consciously measure, transform or use at the output of measuring instruments is not the value that we need, but another one that reflects the desired only approximately, but is much easier to implement.
For the main error, the error of the measuring instrument used under normal conditions specified in the regulatory and technical documents (NTD) is taken. It is known that, along with the sensitivity to the measured value, the measuring instrument has some sensitivity to non-measurable, but influencing quantities, for example, to temperature, atmospheric pressure, vibration, shock, etc. Therefore, any measuring instrument has a basic error, which is reflected in the NTD.
During the operation of measuring and control instruments in production conditions, significant deviations from normal conditions occur, causing additional errors. These errors are normalized by the corresponding coefficients of the influence of changes in individual influencing quantities on the change in indications in the form a; % /10°С; % /10% U„m, etc.
Errors of measuring instruments are normalized by setting the limit of permissible error. The limit of permissible error of a measuring instrument is the largest (without taking into account the sign) error of a measuring instrument at which it can be recognized and allowed for use. For example, the limits of error for a 100-mm end block of the 1st class are ± µm, and for a class 1.0 ammeter they are ±1% of the upper limit of measurements.
In addition, all the listed measurement errors are subdivided by type into systematic, random and gross, static and dynamic error components, absolute and relative (see subsection 1.4).
The errors of measuring instruments can be expressed as:
in the form of absolute error D:
for measure where Hnom - nominal value; Ha - the actual value of the measured value;
for the device where X p - the indication of the device;
In the form of a relative error, %, in the form of a reduced error, %, where XN is the normalizing value of the measured physical quantity.
As a normalizing value, the measurement limit of this SI can be taken. For example, for scales with a mass measurement limit of 10 kg Xc = 10 kg.
If the range of the entire scale is taken as the normalizing quantity, then it is to the value of this range in units of the measured physical quantity that the absolute error is attributed.
For example, for an ammeter with limits from -100 mA to 100 mA X N - 200 mA.
If the scale length of the instrument 1 is taken as a normalizing value, then X# = 1.
For each SI, the error is given in only one form.
If the SI error under constant external conditions is constant over the entire measurement range, then If it changes in the indicated range, then where a, b are positive numbers that do not depend on Xa.
When D = ±a, the error is called additive, and when D = ±(a + + bx) - multiplicative.
For additive error where p is the largest (modulo) of the measurement limits.
For the multiplicative error where c, d are positive numbers chosen from the series; c = b + d;
Reduced error where q is the largest (modulo) of the measurement limits.
Values p, c, d, q are selected from a number of numbers: 1 10”; 1.5 10”;
(1.6-10"); 2-10"; 2.5-10”; 3-10"; 4-10"; 5-10"; 6-10", where n is a positive or negative integer, including 0.
For a generalized characteristic of the accuracy of measuring instruments, determined by the limits of permissible errors (main and additional), as well as their other properties that affect the measurement error, the concept of "accuracy class of measuring instruments" is introduced. GOST 8.401 - 80 “Accuracy classes are convenient for a comparative assessment of the quality of measuring instruments, their choice, international trade” regulates the uniform rules for setting limits for permissible errors of indications by accuracy classes of measuring instruments.
Despite the fact that the accuracy class characterizes the totality of the metrological properties of a given measuring instrument, it does not unambiguously determine the accuracy of measurements, since the latter also depends on the measurement method and the conditions for their implementation.
Accuracy classes are determined by standards and specifications containing technical requirements for measuring instruments. For each accuracy class of a measuring instrument of a specific type, specific requirements for metrological characteristics are established, which together reflect the level of accuracy. Common characteristics for measuring instruments of all accuracy classes (for example, input and output resistances) are standardized regardless of accuracy classes. Instruments for measuring several physical quantities or with several d and measurement ranges may have two or more accuracy classes.
For example, an electrical measuring instrument designed to measure electrical voltage and resistance can be assigned two accuracy classes: one as a voltmeter, the other as an ammeter.
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