Metrology - basic terms and definitions. Basic concepts and terms of metrology Metrological concepts

Without measuring instruments and methods of their application, scientific and technological progress would be impossible. In the modern world, people cannot do without them even in everyday life. Therefore, such a vast layer of knowledge could not help but be systematized and formed as a complete one. The concept of “metrology” is used to define this direction. What are measuring instruments from the point of view of scientific knowledge? One might say that this is a subject of research, but the activities of specialists in this field necessarily have a practical nature.

Metrology concept

IN general idea metrology is often considered as a body of scientific knowledge about means, methods and methods of measurement, which also includes the concept of their unity. For regulation practical application Based on this knowledge, there is a federal agency for metrology, which technically manages the property in the field of metrology.

As you can see, measurement occupies a central place in the concept of metrology. In this context, measurement means obtaining information about the subject of study - in particular information about properties and characteristics. Required condition is precisely the experimental way of obtaining this knowledge using metrological tools. It should also be taken into account that metrology, standardization and certification are closely interrelated and only together can give practical valuable information. So, if metrology deals with development issues, then standardization establishes uniform forms and rules for the application of these same methods, as well as for recording the characteristics of objects in accordance with given standards. As for certification, its goal is to determine the compliance of the object under study with certain parameters established by the standards.

Goals and objectives of metrology

Metrology faces several important challenges, which are located in three areas - theoretical, legislative and practical. As scientific knowledge develops, goals from different directions are mutually complemented and adjusted, but in general, the tasks of metrology can be presented as follows:

Formation of systems of units and characteristics of measurement.
Develop general theoretical knowledge about measurements.
Standardization of measurement methods.
Approval of standards of measurement methods, verification measures and technical means.
Study of the system of measures in the context of historical perspective.

Unity of measurements

The basic level of standardization means that the results of measurements are reflected in an approved format. That is, the measurement characteristic is expressed in its accepted form. Moreover, this applies not only to certain measurement values, but also to errors that can be expressed taking into account probabilities. Metrological unity exists to make it possible to compare results that were carried out under different conditions. Moreover, in each case, the methods and means must remain the same.

If we consider the basic concepts of metrology from the point of view of the quality of results obtained, then the main one will be accuracy. In a sense, it is interrelated with the error, which distorts the readings. It is precisely in order to increase accuracy that serial measurements are used under various conditions, thanks to which it is possible to get a more complete picture of the subject of study. Preventive measures aimed at checking technical equipment, testing new methods, analyzing standards, etc. also play a significant role in improving the quality of measurements.

Principles and methods of metrology

To achieve high quality measurements, metrology relies on several basic principles, including the following:

The Peltier principle, focused on determining the absorbed energy during the flow of ionizing radiation.
Josephson's principle, on the basis of which voltage measurements are made in an electrical circuit.
The Doppler principle, which provides velocity measurements.
The principle of gravity.

For these and other principles, a wide base of methods has been developed with the help of which practical research. It is important to consider that metrology is the science of measurements, which are supported by applied tools. But technical means, on the other hand, are based on specific theoretical principles and methods. Among the most common methods are the direct assessment method, measuring mass on a scale, substitution, comparison, etc.

Measuring instruments

One of the most important concepts in metrology is the means of measurement. As a rule, which reproduces or stores a certain physical quantity. During application, it examines the object, comparing the identified parameter with the reference one. Measuring instruments are a broad group of instruments that have many classifications. According to their design and principle of operation, for example, converters, devices, sensors, devices and mechanisms are distinguished.

A measuring setup is a relatively modern type of device used in metrology. What is this setting in practical use? Unlike the simplest tools, the installation is a machine that contains a whole range of functional components. Each of them may be responsible for one or more measures. An example is laser protractors. They are used by builders to determine a wide range of geometric parameters, as well as for calculations using formulas.

What is error?

Error also plays a significant role in the measurement process. In theory, it is considered as one of the basic concepts of metrology, in this case reflecting the deviation of the obtained value from the true one. This deviation may be random or systematic. In the design of measuring instruments, manufacturers usually include a certain amount of error in the list of characteristics. It is thanks to fixing the possible limits of deviations in the results that we can talk about the reliability of measurements.

But it is not only the error that determines possible deviations. Uncertainty is another characteristic that guides metrology in this regard. What is measurement uncertainty? Unlike error, it practically does not operate with exact or relatively accurate values. It only indicates doubt about a particular result, but, again, does not determine the intervals of deviations that could cause such an attitude towards the obtained value.

Types of metrology by area of application

Metrology in one form or another is involved in almost all areas human activity. In construction, the same measuring instruments are used to record deviations of structures along planes; in medicine, they are used on the basis of the most precise equipment; in mechanical engineering, specialists also use devices that allow them to determine characteristics in the smallest detail. Larger specialized projects are carried out by the agency for technical regulation and metrology, which at the same time maintains a bank of standards, establishes regulations, carries out cataloging, etc. This body, to varying degrees, covers all areas of metrological research, extending approved standards to them.

Conclusion

In metrology, there are previously established and unchanged standards, principles and methods of measurement. But there is also whole line its directions, which cannot remain unchanged. Accuracy is one of the key characteristics that metrology provides. What is accuracy in the context of a measurement procedure? This is a quantity that largely depends on the technical means of measurement. And it is precisely in this area that metrology is developing dynamically, leaving behind outdated, ineffective tools. But this is just one of the most striking examples in which this area is regularly updated.

Basic metrology terms are established by state standards.

1. Basic concept of metrology - measurement. According to GOST 16263-70, measurement is finding the value of a physical quantity (PV) experimentally using special technical means.

The result of a measurement is the receipt of a value during the measurement process.

With the help of measurements, information is obtained about the state of production, economic and social processes. For example, measurements are the main source of information about the compliance of products and services with the requirements of regulatory documentation during certification.

2. Measuring instrument(SI) - a special technical means that stores a unit of quantity for comparing the measured quantity with its unit.

3. Measure is a measuring instrument designed to reproduce a physical quantity of a given size: weights, gauge blocks.

To assess the quality of measurements, the following measurement properties are used: accuracy, convergence, reproducibility and accuracy.

- Correctness- the property of measurements when their results are not distorted by systematic errors.

- Convergence- a property of measurements that reflects the closeness to each other of measurement results performed under the same conditions, by the same measuring instruments, by the same operator.

- Reproducibility- a property of measurements that reflects the closeness to each other of the results of measurements of the same quantity, performed under different conditions - at different times, in different places, with different methods and measuring instruments.

For example, the same resistance can be measured directly with an ohmmeter, or with an ammeter and a voltmeter using Ohm's law. But, naturally, in both cases the results should be the same.

- Accuracy- a property of measurements that reflects the proximity of their results to the true value of the measured value.

This is the main property of measurements, because most widely used in the practice of intentions.

The accuracy of SI measurements is determined by their error. High measurement accuracy corresponds to small errors.

4. Error is the difference between the SI readings (measurement result) Xmeas and the true (actual) value of the measured physical quantity Xd.

The task of metrology is to ensure the uniformity of measurements. Therefore, to generalize all the above terms, use the concept uniformity of measurements- a state of measurements in which their results are expressed in legal units, and errors are known with a given probability and do not go beyond established limits.

Measures to actually ensure the uniformity of measurements in most countries of the world are established by law and are part of the functions of legal metrology. In 1993, the Russian Federation Law “On Ensuring the Uniformity of Measurements” was adopted.

Previously, legal norms were established by government regulations.

Compared to the provisions of these resolutions, the Law established the following innovations:

In terminology - outdated concepts and terms have been replaced;

In licensing metrological activities in the country, the right to issue a license is granted exclusively to the bodies of the State Metrological Service;

A unified verification of measuring instruments has been introduced;

A clear separation of the functions of state metrological control and state metrological supervision has been established.

An innovation is also the expansion of the scope of state metrological supervision to banking, postal, tax, customs operations, as well as to mandatory certification of products and services;

Calibration rules have been revised;

Introduced voluntary certification measuring instruments, etc.

Prerequisites for the adoption of the law:

The country's transition to a market economy;

As a result, the reorganization of state metrological services;

This led to a violation centralized system management of metrological activities and departmental services;

Problems arose during state metrological supervision and control due to the emergence of various forms of ownership;

Thus, the problem of revising the legal, organizational, and economic foundations of metrology has become very urgent.

The objectives of the Law are as follows:

Protecting citizens and the economy Russian Federation from the negative consequences of unreliable measurement results;

Promoting progress based on the use of state standards of units of quantities and the use of measurement results of guaranteed accuracy;

Creating favorable conditions for the development of international relations;

Regulation of relations between government bodies of the Russian Federation and legal entities and individuals on issues of manufacturing, production, operation, repair, sale and import of measuring instruments.

Consequently, the main areas of application of the Law are trade, healthcare, environmental protection, and foreign economic activity.

The task of ensuring the uniformity of measurements is assigned to the State Metrological Service. The law determines the intersectoral and subordinate nature of its activities.

The intersectoral nature of the activity means the legal status of the State Metrological Service is similar to other control and supervisory authorities government controlled(Gosatomnadzor, Gosenergonadzor, etc.).

The subordinate nature of its activities means vertical subordination to one department - Gosstandart of Russia, within the framework of which it exists separately and autonomously.

In pursuance of the adopted Law, the Government of the Russian Federation in 1994 approved a number of documents:

- “Regulations on state scientific and metrological centers”,

- “The procedure for approving regulations on metrological services of federal executive authorities and legal entities”,

- “The procedure for accreditation of metrological services of legal entities for the right to verify measuring instruments”,

These documents, together with the said Law, are the main legal acts in metrology in Russia.

Metrology

Metrology(from Greek μέτρον - measure, + other Greek λόγος - thought, reason) - The subject of metrology is the extraction of quantitative information about the properties of objects with a given accuracy and reliability; the regulatory framework for this is metrological standards.

Metrology consists of three main sections:

Theoretical or fundamental - considers general theoretical problems (development of the theory and problems of measuring physical quantities, their units, measurement methods).
Applied- studies issues of practical application of developments in theoretical metrology. She is in charge of all issues of metrological support.
Legislative- establishes mandatory technical and legal requirements for the use of units of physical quantities, methods and measuring instruments.

Metrologist

Goals and objectives of metrology

Creation general theory measurements;
formation of units of physical quantities and systems of units;
development and standardization of methods and measuring instruments, methods for determining measurement accuracy, the basis for ensuring the uniformity of measurements and uniformity of measuring instruments (the so-called “legal metrology”);
creation of standards and exemplary measuring instruments, verification of measures and measuring instruments. The priority subtask of this direction is to develop a system of standards based on physical constants.

Metrology also studies the development of a system of measures, monetary units and counting in a historical perspective.

Axioms of metrology

Any measurement is a comparison.
Any measurement without a priori information is impossible.
The result of any measurement without rounding the value is random variable.

Metrology terms and definitions

Unity of measurements- a state of measurements, characterized by the fact that their results are expressed in legal units, the sizes of which, within established limits, are equal to the sizes of units reproduced by primary standards, and the errors of the measurement results are known and with a given probability do not go beyond the established limits.
Physical quantity- one of the properties of a physical object, common in qualitative terms for many physical objects, but in quantitative terms individual for each of them.
Measurement- a set of operations for the use of a technical means that stores a unit of physical quantity, ensuring the determination of the relationship of the measured quantity with its unit and obtaining the value of this quantity.
Measuring instrument- a technical device intended for measurements and having standardized metrological characteristics reproducing and (or) storing a unit of quantity, the size of which is assumed to be unchanged within the established error over a known time interval.
Verification- a set of operations performed to confirm the compliance of measuring instruments with metrological requirements.
Measurement error- deviation of the measurement result from the true value of the measured value.
Measuring instrument error- the difference between the reading of the measuring instrument and the actual value of the measured physical quantity.
Measuring instrument accuracy- characteristic of the quality of a measuring instrument, reflecting the proximity of its error to zero.
License- this is a permit issued by the state metrological service authorities on the territory assigned to it to an individual or legal entity to carry out activities for the production and repair of measuring instruments.
Standard unit of quantity- a technical means intended for transmission, storage and reproduction of a unit of value.

History of metrology

Metrology dates back to ancient times and is even mentioned in the Bible. Early forms of metrology involved the establishment of simple arbitrary standards by local authorities, often based on simple practical measurements such as arm length. The earliest standards were introduced for quantities such as length, weight and time, this was done to simplify commercial transactions as well as recording human activities.

Metrology acquired a new meaning during the era of the industrial revolution; it became absolutely necessary to ensure mass production.

Historically important stages in the development of metrology:

XVIII century - establishment of the meter standard (the standard is kept in France, in the Museum of Weights and Measures; currently it is more of a historical exhibit than a scientific instrument);
1832 - creation of absolute systems of units by Carl Gauss;
1875 - signing of the international Meter Convention;
1960 - development and establishment of the International System of Units (SI);
20th century - metrological studies of individual countries are coordinated by International Metrological Organizations.

Milestones national history metrology:

accession to the Meter Convention;
1893 - creation by D.I. Mendeleev of the Main Chamber of Weights and Measures (modern name: “Mendeleev Research Institute of Metrology”);

World Metrology Day is celebrated annually on May 20. The holiday was established by the International Committee of Weights and Measures (CIPM) in October 1999, at the 88th meeting of the CIPM.

The formation and differences of metrology in the USSR (Russia) and abroad

The rapid development of science, technology and technology in the twentieth century required the development of metrology as a science. In the USSR, metrology developed as a state discipline, as the need to improve the accuracy and reproducibility of measurements grew with industrialization and the growth of the military-industrial complex. Foreign metrology was also based on practical requirements, but these requirements came mainly from private firms. An indirect consequence of this approach was state regulation of various concepts related to metrology, that is, GOST regulation of everything that needs to be standardized. Abroad, non-governmental organizations such as ASTM have taken on this task.

Due to this difference in metrology of the USSR and post-Soviet republics state standards(standards) are recognized as dominant, in contrast to the competitive Western environment, where a private company may not use an objectionable standard or instrument and agree with its partners on another option for certifying the reproducibility of measurements.

Selected areas of metrology

Aviation metrology
Chemical metrology
Medical metrology
Biometrics

The science of measurements, methods and means of ensuring their unity and ways of achieving the required accuracy.

MEASUREMENT

UNITY OF MEASUREMENT

1. Physical quantities

PHYSICAL QUANTITY (PV)

ACTUAL PV VALUE

PHYSICAL PARAMETER

Influential fv

ROD FV

Qualitative certainty FV.

Part length and diameter-

UNIT FV

PV UNIT SYSTEM

DERIVATIVE UNIT

Unit of speed- meter/second.

NON-SYSTEM UNIT FV

allowed equally;.

temporarily admitted;

withdrawn from use.

For example:

- - units of time;

in optics- diopter- - hectare- - unit of energy, etc.;

- revolutions per second; bar- pressure unit (1bar = 100 000 Pa);

quintal, etc.

MULTIPLE UNIT OF FV

DOLNAYA FV

For example, 1µs= 0.000 001s.

Basic terms and definitions metrology

The science of measurements, methods and means of ensuring their unity and ways of achieving the required accuracy.

MEASUREMENT

Finding the value of a measured physical quantity experimentally using special technical means.

UNITY OF MEASUREMENT

A characteristic of the quality of measurements, which consists in the fact that their results are expressed in legal units, and the errors of the measurement results are known with a given probability and do not go beyond the established limits.

ACCURACY OF MEASUREMENT RESULTS

A characteristic of the quality of a measurement, reflecting the closeness to zero of the error of its result.

1. Physical quantities

PHYSICAL QUANTITY (PV)

A characteristic of one of the properties of a physical object (physical system, phenomenon or process), which is qualitatively common to many physical objects, but quantitatively individual for each object.

THE TRUE VALUE OF A PHYSICAL QUANTITY

The value of a physical quantity that ideally reflects the corresponding physical quantity in qualitative and quantitative terms.

This concept is correlated with the concept of absolute truth in philosophy.

ACTUAL PV VALUE

The value of the PV, found experimentally and so close to the true value that for the given measurement task it can replace it.

When checking measuring instruments, for example, the actual value is the value of the standard measure or the reading of the standard measuring instrument.

PHYSICAL PARAMETER

EF, considered when measuring a given EF as an auxiliary characteristic.

For example, frequency when measuring AC voltage.

Influential fv

PV, the measurement of which is not provided for by a given measuring instrument, but which influences the measurement results.

ROD FV

Qualitative certainty FV.

Part length and diameter- homogeneous quantities; the length and mass of the part are non-uniform quantities.

UNIT FV

FV of a fixed size, which is conditionally assigned numeric value, equal to unity, and used for the quantitative expression of homogeneous PVs.

There must be as many units as there are PVs.

There are basic, derivative, multiple, submultiple, systemic and non-systemic units.

PV UNIT SYSTEM

A set of basic and derived units of physical quantities.

BASIC UNIT OF THE SYSTEM OF UNITS

The unit of basic PV in a given system of units.

Basic units of the International System of Units SI: meter, kilogram, second, ampere, kelvin, mole, candela.

ADDITIONAL UNIT SYSTEM OF UNITS

There is no strict definition. In the SI system, these are the units of plane - radians - and solid - steradians - angles.

DERIVATIVE UNIT

A unit of a derivative of a PV system of units, formed in accordance with an equation connecting it with the basic units or with the basic and already defined derived units.

Unit of speed- meter/second.

NON-SYSTEM UNIT FV

The PV unit is not included in any of the accepted systems of units.

Non-systemic units in relation to the SI system are divided into four types:

allowed equally;.

approved for use in special areas;

temporarily admitted;

withdrawn from use.

For example:

ton: degree, minute, second- angle units; liter; minute, hour, day, week, month, year, century- units of time;

in optics- diopter- unit of measurement of optical power; in agriculture- hectare- unit of area; in physics electron-volt- unit of energy, etc.;

in maritime navigation, nautical mile, knot; in other areas- revolutions per second; bar- pressure unit (1bar = 100 000 Pa);

kilogram-force per square centimeter; millimeter of mercury; Horsepower;

quintal, etc.

MULTIPLE UNIT OF FV

A PV unit is an integer number of times larger than a system or non-system unit.

For example, frequency unit 1 MHz = 1,000,000 Hz

DOLNAYA FV

A PV unit is an integer number of times smaller than a system or non-system unit.

For example, 1µs= 0.000 001s.

Basic terms and definitions in metrology

Metrology– the science of measurements, methods and means of ensuring their unity and methods of achieving the required accuracy.

Direct measurement– a measurement in which the desired value of a physical quantity is obtained directly.

Indirect measurement– determination of the desired value of a physical quantity based on the results of direct measurements of other physical quantities that are functionally related to the desired quantity.

True value of a physical quantity– the value of a physical quantity that ideally characterizes the corresponding physical quantity in qualitative and quantitative terms.

Real value of a physical quantity– the value of a physical quantity obtained experimentally and so close to the true value that it can be used instead of it in the given measurement task.

Measured physical quantity– physical quantity to be measured in accordance with the main purpose of the measurement task.

Influential physical quantity– a physical quantity that influences the size of the measured quantity and (or) the result of measurements.

Normal range of influence quantities– the range of values of the influencing quantity, within which the change in the measurement result under its influence can be neglected in accordance with established accuracy standards.

Working range of influencing quantities– range of values of the influencing quantity, within which the additional error or change in the readings of the measuring instrument is normalized.

Measuring signal– a signal containing quantitative information about the measured physical quantity.

Scale division price– the difference in values corresponding to two adjacent scale marks.

Measuring instrument reading range– range of instrument scale values, limited by the initial and final scale values.

Measuring range– range of values of a quantity within which the permissible error limits of the measuring instrument are normalized.

Variation of indications measuring instrument – the difference in instrument readings at the same point in the measurement range with a smooth approach to this point from smaller and larger values of the measured value.

Transducer conversion factor– the ratio of the signal at the output of the measuring transducer, which displays the measured value, to the signal causing it at the input of the transducer.

Sensitivity of the measuring instrument– property of a measuring instrument, determined by the ratio of the change in the output signal of this instrument to the change in the measured value that causes it

Absolute error of the measuring instrument– the difference between the reading of a measuring instrument and the true (actual) value of the measured quantity, expressed in units of the measured physical quantity.

Relative error of the measuring instrument– error of a measuring instrument, expressed as the ratio of the absolute error of the measuring instrument to the measurement result or to the actual value of the measured physical quantity.

Reduced error of the measuring instrument– relative error, expressed as the ratio of the absolute error of the measuring instrument to the conventionally accepted value of a quantity (or standard value), constant over the entire measurement range or in part of the range. Often the reading range or upper measurement limit is taken as the normalizing value. The given error is usually expressed as a percentage.

Systematic error of the measuring instrument– component of the error of a measuring instrument, taken as constant or naturally varying.

Random error of the measuring instrument– component of the error of the measuring instrument, varying randomly.

Basic error of the measuring instrument– error of the measuring instrument used under normal conditions.

Additional error of the measuring instrument– a component of the error of a measuring instrument that arises in addition to the main error as a result of the deviation of any of the influencing quantities from its normal value or as a result of going beyond the normal range of values.

Limit of permissible error of measuring instrument – highest value error of measuring instruments, established by a regulatory document for a given type of measuring instrument, at which it is still recognized as suitable for use.

Measuring instrument accuracy class– a generalized characteristic of a given type of measuring instrument, usually reflecting the level of their accuracy, expressed by the limits of permissible main and additional errors, as well as other characteristics affecting the accuracy.

Measurement result error– deviation of the measurement result from the true (actual) value of the measured quantity.

Miss (gross measurement error)– the error of the result of an individual measurement included in a series of measurements, which, for given conditions, differs sharply from the other results of this series.

Measurement method error– component of the systematic measurement error due to the imperfection of the adopted measurement method.

Amendment– the value of the quantity entered into the uncorrected measurement result in order to eliminate the components of the systematic error. The sign of the correction is opposite to the sign of the error. The correction introduced into the reading of a measuring device is called an amendment to the reading of the device.

Basic terms and definitions metrology

The science of measurements, methods and means of ensuring their unity and ways of achieving the required accuracy.

MEASUREMENT

Finding the value of a measured physical quantity experimentally using special technical means.

UNITY OF MEASUREMENT

ACCURACY OF MEASUREMENT RESULTS

A characteristic of the quality of a measurement, reflecting the closeness to zero of the error of its result.

1. Physical quantities

PHYSICAL QUANTITY (PV)

THE TRUE VALUE OF A PHYSICAL QUANTITY

The value of a physical quantity that ideally reflects the corresponding physical quantity in qualitative and quantitative terms.

This concept is correlated with the concept of absolute truth in philosophy.

ACTUAL PV VALUE

The value of the PV, found experimentally and so close to the true value that for the given measurement task it can replace it.

When checking measuring instruments, for example, the actual value is the value of the standard measure or the reading of the standard measuring instrument.

PHYSICAL PARAMETER

EF, considered when measuring a given EF as an auxiliary characteristic.

For example, frequency when measuring AC voltage.

Influential fv

PV, the measurement of which is not provided for by a given measuring instrument, but which influences the measurement results.

ROD FV

Qualitative certainty FV.

Part length and diameter- homogeneous quantities; the length and mass of the part are non-uniform quantities.

UNIT FV

A PV of a fixed size, which is conventionally assigned a numerical value equal to one, and is used for the quantitative expression of homogeneous PV.

There must be as many units as there are PVs.

There are basic, derivative, multiple, submultiple, systemic and non-systemic units.

PV UNIT SYSTEM

A set of basic and derived units of physical quantities.

BASIC UNIT OF THE SYSTEM OF UNITS

The unit of basic PV in a given system of units.

Basic units of the International System of Units SI: meter, kilogram, second, ampere, kelvin, mole, candela.

ADDITIONAL UNIT SYSTEM OF UNITS

There is no strict definition. In the SI system, these are the units of plane - radians - and solid - steradians - angles.

DERIVATIVE UNIT

A unit of a derivative of a PV system of units, formed in accordance with an equation connecting it with the basic units or with the basic and already defined derived units.

Unit of speed- meter/second.

NON-SYSTEM UNIT FV

The PV unit is not included in any of the accepted systems of units.

Non-systemic units in relation to the SI system are divided into four types:

allowed equally;.

approved for use in special areas;

temporarily admitted;

withdrawn from use.

For example:

ton: degree, minute, second- angle units; liter; minute, hour, day, week, month, year, century- units of time;

in optics- diopter- unit of measurement of optical power; in agriculture- hectare- unit of area; in physics electron-volt- unit of energy, etc.;

in maritime navigation, nautical mile, knot; in other areas- revolutions per second; bar- pressure unit (1bar = 100 000 Pa);

kilogram-force per square centimeter; millimeter of mercury; Horsepower;

quintal, etc.

MULTIPLE UNIT OF FV

A PV unit is an integer number of times larger than a system or non-system unit.

For example, frequency unit 1 MHz = 1,000,000 Hz

DOLNAYA FV

A PV unit is an integer number of times smaller than a system or non-system unit.

For example, 1µs= 0.000 001s.

Metrology Basic terms and definitions

UDC 389.6(038):006.354 Group T80

STATE SYSTEM FOR ENSURING THE UNIFORMITY OF MEASUREMENTS

State system for ensuring the uniformity of measurements.

Metrology. Basic terms and definitions

ISS 01.040.17

Date of introduction 2001-01-01

Preface

1 DEVELOPED by the All-Russian Scientific Research Institute of Metrology named after. D.I. Mendeleev Gosstandart of Russia

INTRODUCED by the Technical Secretariat of the Interstate Council for Standardization, Metrology and Certification

2 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (Minutes No. 15 of May 26-28, 1999)

State name	Name of the national standardization body
The Republic of Azerbaijan	Azgosstandart
Republic of Armenia	Armgosstandard
Republic of Belarus	State Standard of Belarus
	Gruzstandart
The Republic of Kazakhstan	Gosstandart of the Republic of Kazakhstan
The Republic of Moldova	Moldovastandard
Russian Federation	Gosstandart of Russia
The Republic of Tajikistan	Tajikgosstandart
Turkmenistan	Main State Inspectorate of Turkmenistan
The Republic of Uzbekistan	Uzgosstandart
	State Standard of Ukraine

3 Decree State Committee Russian Federation on standardization and metrology dated May 17, 2000 No. 139-st interstate Recommendations RMG 29-99 came into force directly as Recommendations on metrology of the Russian Federation from January 1, 2001.

4 INSTEAD GOST 16263-70

5 REPUBLICATION. September 2003

Amendment No. 1 was introduced, adopted by the Interstate Council for Standardization, Metrology and Certification (Minutes No. 24 of December 5, 2003) (IUS No. 1 of 2005)

Introduction

The terms established by these recommendations are arranged in a systematic order, reflecting the established system of basic concepts of metrology. Terms are given in sections 2-13. Each section contains continuous numbering of terms.

For each concept, one term is established, which has a terminological article number. A significant number of terms are accompanied by their short forms and (or) abbreviations, which should be used in cases that exclude the possibility of their different interpretations.

Terms that have the number of a terminological article are typed in bold, their short forms and abbreviations are in light. Terms appearing in the notes are in italics.

In the alphabetical index of terms in Russian, the specified terms are listed in alphabetical order, indicating the number of the terminological article (for example, “value 3.1”). In this case, for terms given in the notes, the letter “p” is indicated after the article number (for example, legalized units 4.1 p).

For many established terms, foreign language equivalents are provided in German (de), English (en) and French (fr). They are also listed in alphabetical indexes of equivalent terms in German, English and French.

The word “applied” in term 2.4, given in brackets, as well as the words of a number of foreign language equivalents of terms given in brackets, can be omitted if necessary.

The concept of “additional unit” is not defined, since the term fully discloses its content.

In this article we will find out what metrology is. Scientific and technological progress is quite difficult to imagine without methods and measuring instruments. Even in many everyday matters we cannot do without them. For this reason, such a large-scale and all-encompassing body of knowledge could not remain without systematization and separation into a separate branch of science. This scientific direction is called metrology. She explains the various means of measurement from a scientific point of view. This is the subject of metrology research. However, the activities of metrology specialists also include a practical component.

What is metrology

The International Dictionary of Basic and General Terms in Metrology defines this concept as the science of measurement. Metrology, as well as any types of measurements, plays a significant role in almost all areas of human activity. They are used everywhere, including production control, environmental quality, human safety and health, as well as the evaluation of materials, food products, fair trading and consumer protection. What is the basis of metrology?

The concept of “metrological infrastructure” is used quite often. It applies to the measuring capacities of a region or a country as a whole and involves the work of testing and calibration services, laboratories and metrological institutes, as well as the management and organization of the metrology system.

Basic Concepts

The concept of “metrology” is most often used in a generalized sense, implying not only the theoretical, but also the practical aspects of the measuring system. If you need to specify the scope of application, the following concepts are usually used.

General metrology

What is this type of metrology? It deals with issues that are common to all areas of metrological measurements. General metrology deals with practical and theoretical issues that affect measurement units, namely the structure of a system of units, as well as the transformation of measurement units within formulas. She also deals with the problem of measurement errors, measurement instruments and metrological properties. Quite often, general metrology is also called scientific. General metrology covers various areas, for example:

Industrial metrology

What is metrology used in industry? This branch of science deals with production measurements as well as quality testing. The main problems faced by industrial or technical metrology are calibration intervals and procedures, control of measurement equipment, verification of the measurement process, etc. Quite often this concept is used in describing metrological activities in the industrial sector.

Legal metrology

This term is included in the list of mandatory requirements from a technical point of view. Organizations related to the field of legal metrology are engaged in checking the implementation of these requirements in order to determine the reliability and correctness of the measurement procedures performed. This applies to public spheres such as health, trade, security and the environment. The areas covered by legal metrology depend on the relevant regulations for each individual country.

Let's look at the basics of metrology in more detail below.

Basics

The subject of metrology is the production of information in certain units of measurement, containing information about the properties of the object under consideration, as well as processes, according to established reliability and accuracy.

Metrology means mean a set of measuring instruments and generally accepted standards that allow for their rational use. Standardization and metrology are closely related.

Objects

Metrology objects include:

Any quantity that is being measured.
Unit of physical quantity.
Measurement.
Measuring error.
Method of taking measurements.
The means by which the measurement is made.

Significance criteria

There are also certain criteria that determine the social significance of metrological work. These include:

Providing reliable and maximally objective information about the measurements taken.
Protecting society from incorrect measurement results to ensure safety.

Goals

The main goals of technical regulation and metrology are:

Improving the quality of products from domestic manufacturers and increasing their competitiveness. This concerns increasing production efficiency, automation and mechanization of the product creation process.
Adapting Russian industry to general market requirements and overcoming technical barriers in the field of trade.
Saving various types of resources.
Increasing the efficiency of cooperation in the international market.
Maintaining records of manufactured products and material resources.

Tasks

The tasks of metrology include:

Development of measurement theory.
Development of new tools and methods for carrying out measurements.
Ensuring uniform measurement rules.
Improving the quality of equipment used for measurement work.
Certification of measurement equipment according to current regulations.
Improvement of documents regulating basic issues of metrology.
Improving the qualifications of personnel who provide the measurement process.

Kinds

Measurements are classified according to a number of factors, namely by the method of obtaining information, by the nature of changes, by the amount of information to be measured, in relation to normal indicators. There are such types of metrology.

According to the way in which information is obtained, direct and indirect, as well as joint and cumulative measurements are distinguished.

What are the means of metrology?

Direct and indirect measurements

Straight lines mean the physical comparison of measure and magnitude. So, for example, when measuring the length of an object using a ruler, the quantitative expression of the length value is compared with the object of the measure.

Indirect measurements involve establishing the desired value of a quantity as a result of direct measurements of indicators related in a certain way to the quantity being tested. For example, when measuring current strength an ammeter, and a voltmeter - voltage, taking into account the relationship of the functional nature of all quantities, it is possible to calculate the power of the entire electrical circuit.

Aggregate and joint measurements

Cumulative measurements involve solving equations in a system obtained as a result of measuring several quantities of the same type simultaneously. The required value is calculated by solving this system of equations.

Joint measurements are the determination of two or more physical quantities of different types in order to calculate the relationship between them. The last two types of measurements are quite often used in the field of electrical engineering to determine different types parameters.

Based on the nature of changes in value during measurement procedures, dynamic, statistical and static measurements are distinguished.

Statistical

Statistical measurements are those that are associated with the identification of characteristics. random processes, noise level, sound signals, etc. Static changes, on the contrary, are characterized by a constant measured value.

Dynamic measurements include measurements of quantities that tend to change during metrological work. Dynamic and static measurements are quite rarely found in ideal form in practice.

Multiple and single

Based on the amount of information, measurements are divided into multiple and single. Single measurement means one measurement of one quantity. Thus, the number of measurements is completely related to the quantities that are measured. The use of this type of measurement is associated with significant errors in calculation, and therefore requires the derivation of an arithmetic average value after several metrological procedures.

Multiple measurements are those that are characterized by an excess of the number of metrological operations over the measured values. The main advantage of this type of measurement is the insignificant influence of random factors on the error.

Absolute and relative

In relation to the basic metrological units, absolute and relative measurements are distinguished.

Absolute measurements involve the use of one or more fundamental quantities coupled with a constant. Relative ones are based on the ratio of a metrological quantity to a homogeneous quantity used as a unit.

Measurement scale

Concepts such as measurement scale, principles and methods are directly related to metrology.

A measurement scale is understood as a systematized set of values of a quantity in its physical expression. It is convenient to consider the concept of a measurement scale using the example of temperature scales.

The temperature at which ice melts is the starting point, and the reference point is the temperature at which water boils. One hundredth of the above-described interval is taken as one temperature unit, that is, a degree Celsius. There is also a temperature scale in Fahrenheit, the starting point of which is the melting temperature of a mixture of ice and ammonia, and normal body temperature is taken as the reference point. One Fahrenheit unit is ninety-sixth of an interval. On this scale, ice melts at 32 degrees, and water boils at 212. Thus, it turns out that the interval in Celsius is 100 degrees, and in Fahrenheit 180.

In the metrology system, other types of scales are also known, for example, names, order, intervals, ratios, etc.

The scale of names implies a qualitative, but not a quantitative unit. This type of scale does not have a starting point, a reference point, or metrological units. An example of such a scale would be a color atlas. It is used to visually correlate a painted item with reference samples included in the atlas. Since there can be a great variety of shade options, the comparison should be made by an experienced specialist who has extensive practical experience in this field, as well as special visual abilities.

The order scale is characterized by the value of the measurement value expressed in points. These could be scales of earthquakes, hardness of bodies, wind force, etc.

The difference or interval scale has relative zero values. Intervals on this scale are determined by agreement. This group includes length and time scales.

The ratio scale has a specific zero value, and the metrological unit is determined by agreement. The mass scale, for example, can be calibrated in different ways, taking into account the required weighing accuracy. Analytical and household scales differ significantly from each other.

Conclusion

Thus, metrology takes part in all practical and theoretical areas of human activity. In the construction field, measurements are used to determine the deflections of a structure in certain planes. In the medical field, precise equipment makes it possible to carry out diagnostic procedures, the same applies to mechanical engineering, where specialists use devices that make it possible to make calculations with maximum accuracy.

There are also special metrology centers that carry out technical regulation and carry out large-scale projects, as well as establish regulations and carry out systematization. Such agencies extend their influence to all types of metrological studies, applying established standards to them. Despite the accuracy of many indicators used in metrology, this science, like all others, continues to move forward and undergoes certain changes and additions.

Metrology – the science of measurements, methods and means of ensuring their unity and ways of achieving the required accuracy.

Theoretical (fundamental) metrology – a section of metrology whose subject is the development of the fundamental principles of metrology.

Legal metrology – a section of metrology, the subject of which is the establishment of mandatory technical and legal requirements for the use of units of physical quantities, standards, methods and measuring instruments aimed at ensuring the unity and the need for accuracy of measurements in the interests of society.

Practical (applied) metrology – a section of metrology, the subject of which is the practical application of the developments of theoretical metrology and the provisions of legal metrology.

(Graneev)

Physical quantity - a property that is common in qualitative terms for many objects and individual in quantitative terms for each of them.

Size of physical quantity – quantitative content of a property (or expression of the size of a physical quantity) corresponding to the concept of “physical quantity” inherent in a given object .

Physical quantity value - quantitative assessment of the measured value in the form of a certain number of units accepted for a given value.

Unit of measurement of physical quantity – a physical quantity of a fixed size, which is assigned a numerical value equal to one, and is used for the quantitative expression of physical quantities similar to it.

When making measurements, the concepts of true and actual value of a physical quantity are used. True value of a physical quantity – the value of a quantity that ideally characterizes the corresponding physical quantity in qualitative and quantitative terms. Real value of a physical quantity is a value of a physical quantity obtained experimentally and so close to the true value that it can be used instead of it in the given measurement task.

Measurement - finding the value of a physical quantity experimentally using special technical means.

The main features of the concept of “measurement”:

a) you can measure the properties of really existing objects of knowledge, i.e. physical quantities;

b) measurement requires experiments, i.e. theoretical reasoning or calculations cannot replace experiment;

c) experiments require special technical means - measuring instruments, brought into interaction with a material object;

G) measurement result is the value of a physical quantity.

Characteristics of measurements: principle and method of measurement, result, error, accuracy, convergence, reproducibility, correctness and reliability.

Measuring principle – physical phenomenon or effect underlying measurements. For example:

Method of measurement - a technique or set of techniques for comparing a measured physical quantity with its unit in accordance with the implemented measurement principle. For example:

Measurement result – the value of a quantity obtained by measuring it.

Measurement result error – deviation of the measurement result from the true (actual) value of the measured quantity.

Accuracy of measurement result – one of the characteristics of measurement quality, reflecting the closeness to zero error of the measurement result.

Convergence of measurement results – closeness to each other of the results of measurements of the same quantity, performed repeatedly by the same means, by the same method under the same conditions and with the same care. The accuracy of measurements reflects the influence of random errors on the measurement result.

Reproducibility – closeness of measurement results of the same quantity obtained in different places, by different methods and means, by different operators, in different time, but reduced to the same conditions (temperature, pressure, humidity, etc.).

Correctness – a characteristic of the quality of measurements, reflecting the closeness to zero of systematic errors in their results.

Credibility – a characteristic of the quality of measurements, reflecting confidence in their results, which is determined by the probability (confidence) that the true value of the measured quantity is within the specified limits (confidence).

A set of quantities interconnected by dependencies form a system of physical quantities. Units that form a system are called system units, and units that are not included in any of the systems are called non-system units.

In 1960 The 11th General Conference on Weights and Measures approved the International System of Units - SI, which includes the ISS system of units ( mechanical units) and the MCSA system (electrical units).

Systems of units are built from basic and derived units. Basic units form a minimal set of independent parent units, and derived units are different combinations of basic units.

Types and methods of measurements

To perform measurements, it is necessary to carry out the following measurement operations: reproduction, comparison, measurement conversion, scaling.

Reproducing the value of the specified size – the operation of creating an output signal with a given size of an informative parameter, i.e. the value of voltage, current, resistance, etc. This operation is implemented by a measuring instrument - a measure.

Comparison – determination of the relationship between homogeneous quantities, carried out by subtracting them. This operation is implemented by a comparison device (comparator).

Measurement conversion – the operation of converting an input signal into an output signal, implemented by a measuring transducer.

Scaling – creating an output signal that is homogeneous with the input signal, the size of the informative parameter of which is proportional to K times the size of the informative parameter of the input signal. Large-scale conversion is implemented in a device called scale converter.

Measurement classification:

by number of measurements – one-time, when measurements are performed once, and multiple– a series of single measurements of a physical quantity of the same size;

accuracy characteristics – equally accurate- this is a series of measurements of any quantity, performed with the same precision measuring instruments under the same conditions with the same care, and unequal when a series of measurements of any quantity are performed with measuring instruments that differ in accuracy and under different conditions;

the nature of the change in time of the measured quantity – static, when the value of a physical quantity is considered constant throughout the measurement time, and dynamic– measurements varying in size of a physical quantity;

method of presenting measurement results – absolute measuring a quantity in its units, and relative– measurements of changes in a quantity in relation to a quantity of the same name, taken as the initial one.

the method of obtaining the measurement result (the method of processing experimental data) - direct and indirect, which are divided into cumulative or joint.

Direct measurement - measurement in which the desired value of a quantity is found directly from experimental data as a result of performing a measurement. An example of direct measurement is measuring the source voltage with a voltmeter.

Indirect measurement - measurement in which the desired value of a quantity is found on the basis of a known relationship between this quantity and quantities subjected to direct measurements. In indirect measurement, the value of the measured quantity is obtained by solving the equation x =F(x1, x2, x3,...., Xn), Where x1, x2, x3,...., Xn- values of quantities obtained by direct measurements.

An example of indirect measurement: the resistance of the resistor R is found from the equation R=U/I, into which the measured voltage drop values are substituted U on the resistor and current I through it.

Joint measurements - simultaneous measurements of several different quantities to find the relationship between them. In this case, the system of equations is solved

F(x1, x2, x3, ...., xn, x1́, x2́, x3́, ...., xḿ) = 0;

F(x1, x2, x3, ...., xn, x1΄΄, x2΄΄, x3΄΄, ...., xm΄΄) = 0;

…………………………………………………

F(x1, x2, x3, ...., xn, x1(n), x2(n), x3(n), ...., xm(n)) = 0,

where x1, x2, x3, ...., xn are the required quantities; x1́, x2́, x3́, ...., xḿ; x1΄΄, x2΄΄, x3΄΄, ...., xm΄΄; x1(n) , x2(n), x3(n), ...., xm(n) - values of measured quantities.

Example of joint measurement: determine the dependence of the resistor resistance on temperature Rt = R0(1 + At + Bt2); By measuring the resistance of the resistor at three different temperatures, they create a system of three equations, from which the parameters R0, A and B are found.

Aggregate Measurements - simultaneous measurements of several quantities of the same name, in which the desired values of the quantities are found by solving a system of equations composed of the results of direct measurements of various combinations of these quantities.

Example of cumulative measurement: measuring the resistances of delta-connected resistors by measuring the resistances between the different vertices of the triangle; Based on the results of three measurements, the resistance of the resistors is determined.

The interaction of measuring instruments with an object is based on physical phenomena, the totality of which is measurement principle , and the set of techniques for using the principle and measuring instruments is called measurement method .

Measurement methods classified according to the following criteria:

according to the physical principle underlying the measurement - electrical, mechanical, magnetic, optical, etc.;

the degree of interaction between the means and the object of measurement - contact and non-contact;

mode of interaction between the means and the measurement object - static and dynamic;

type of measuring signals – analog and digital;

organization of comparison of the measured value with the measure - methods of direct assessment and comparison with the measure.

At direct assessment method (count) the value of the measured quantity is determined directly from the reading device of a direct conversion measuring device, the scale of which was previously calibrated using a multi-valued measure that reproduces the known values of the measured quantity. In direct conversion devices, during the measurement process, the operator compares the position of the pointer of the reading device and the scale on which the reading is made. Measuring current with an ammeter is an example of direct estimation measurement.

Methods for comparison with a measure - methods in which a comparison is made of the measured value and the value reproduced by the measure. Comparison can be direct or indirect through other quantities that are uniquely related to the first. Distinctive feature comparison methods is the direct participation in the process of measuring a measure of a known quantity that is homogeneous with the one being measured.

The group of comparison methods with a measure includes the following methods: zero, differential, substitution and coincidence.

At zero method measurement, the difference between the measured quantity and the known quantity or the difference between the effects produced by the measured and known quantities is reduced to zero during the measurement process, which is recorded by a highly sensitive device - a null indicator. With high accuracy of measures reproducing a known value and high sensitivity of the null indicator, high measurement accuracy can be achieved. An example of the application of the zero method is to measure the resistance of a resistor using a four-arm bridge, in which the voltage drop across the resistor

with unknown resistance is balanced by the voltage drop across a resistor of known resistance.

At differential method the difference between the measured value and the value of a known, reproducible measure is measured using a measuring device. The unknown quantity is determined from the known quantity and the measured difference. In this case, the balancing of the measured value with a known value is not carried out completely, and this is the difference between the differential method and the zero method. The differential method can also provide high measurement accuracy if the known quantity is reproduced with high accuracy and the difference between it and the unknown quantity is small.

An example of a measurement using this method is the measurement of voltage Ux direct current using a discrete voltage divider R U and a voltmeter V (Fig. 1). Unknown voltage Ux = U0 + ΔUx, where U0 is the known voltage, ΔUx is the measured voltage difference.

At substitution method The measured quantity and the known quantity are alternately connected to the input of the device, and the value of the unknown quantity is estimated from the two readings of the device. The smallest measurement error is obtained when, as a result of selecting a known value, the device produces the same output signal as with an unknown value. With this method, high measurement accuracy can be obtained with a high precision measure of a known quantity and high sensitivity of the device. An example of this method is the accurate measurement of a small voltage using a highly sensitive galvanometer, to which first a source of unknown voltage is connected and the deflection of the pointer is determined, and then using an adjustable source of known voltage the same deflection of the pointer is achieved. In this case, the known voltage is equal to the unknown.

At matching method measure the difference between the measured value and the value reproduced by the measure, using the coincidence of scale marks or periodic signals. An example of this method is measuring the rotation speed of a part using a flashing strobe lamp: observing the position of the mark on the rotating part at the moments of the lamp flashes, the frequency of rotation of the part is determined by the frequency of the flashes and the displacement of the mark.

CLASSIFICATION OF MEASUREMENT INSTRUMENTS

Measuring instrument (MI) – a technical device intended for measurements, standardized metrological characteristics, reproducing and (or) storing a unit of physical quantity, the size of which is assumed to be unchanged (within the established error) for a known time interval.

According to their purpose, measuring instruments are divided into measures, measuring transducers, measuring instruments, measuring installations and measuring systems.

Measure – 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. There are measures:

- unambiguous– reproducing a physical quantity of the same size;

- polysemantic – reproducing physical quantities of different sizes;

- set of measures– a set of measures of different sizes of the same physical quantity, intended for practical use both individually and in various combinations;

- store measures – a set of measures structurally combined into a single device, which contains devices for connecting them in various combinations.

Transducer – a technical device with standard metrological characteristics, used to convert a measured value into another value or measuring signal convenient for processing. This conversion must be performed with a given accuracy and provide the required functional relationship between the output and input values of the converter.

Measuring transducers can be classified according to the following criteria:

According to the nature of the transformation, the following types of measuring transducers are distinguished: electrical quantities into electrical ones, magnetic quantities into electrical ones, non-electrical quantities into electrical ones;

The place in the measuring circuit and functions are distinguished between primary, intermediate, scale, and transmitting converters.

Measuring device - a measuring instrument designed to obtain values of a measured physical quantity within a specified range.

Measuring instruments are divided into:

according to the form of registration of the measured value - analogue and digital;

application - ammeters, voltmeters, frequency meters, phase meters, oscilloscopes, etc.;

purpose – instruments for measuring electrical and non-electrical physical quantities;

action – integrating and summing;

method of indicating the values of the measured quantity - indicating, signaling and recording;

method of converting the measured value - direct assessment (direct conversion) and comparison;

method of application and design - panel, portable, stationary;

protection from external conditions - ordinary, moisture-, gas-, dust-proof, sealed, explosion-proof, etc.

Measuring installations – a set of functionally combined measures, measuring instruments, measuring transducers and other devices, intended for measuring one or more physical quantities and located in one place.

Measuring system – a set of functionally combined measures, measuring instruments, measuring transducers, computers and other technical means located at different points of a controlled object for the purpose of measuring one or more physical quantities characteristic of this object and generating measuring signals for various purposes. Depending on their purpose, measuring systems are divided into information, monitoring, control, etc.

Measuring and computing complex – a functionally integrated set of measuring instruments, computers and auxiliary devices, designed to perform a specific measuring task as part of a measuring system.

According to their metrological functions, measuring instruments are divided into standards and working measuring instruments.

Standard unit of physical quantity – a measuring instrument (or a set of measuring instruments) intended for reproducing and (or) storing a unit and transferring its size to subordinate measuring instruments in the verification scheme and approved as a standard in the prescribed manner.

Working measuring instrument – This is a measuring instrument used in measurement practice and not associated with the transfer of units of size of physical quantities to other measuring instruments.

METROLOGICAL CHARACTERISTICS OF MEASUREMENT INSTRUMENTS

Metrological characteristics of the measuring instrument – a characteristic of one of the properties of a measuring instrument that affects the result and error of its measurements. Metrological characteristics established by regulatory and technical documents are called standardized metrological characteristics, and those determined experimentally – actual metrological characteristics.

Conversion function (static conversion characteristic) – functional relationship between the informative parameters of the output and input signals of a measuring instrument.

SI error – the most important metrological characteristic, defined as the difference between the reading of a measuring instrument and the true (actual) value of the measured quantity.

SI sensitivity – property of a measuring instrument, determined by the ratio of the change in the output signal of this instrument to the change in the measured value that causes it. There are absolute and relative sensitivity. Absolute sensitivity is determined by the formula

Relative sensitivity - according to the formula

where ΔY is the change in the output signal; ΔX – change in the measured value, X – measured value.

Scale division price ( device constant ) – the difference in the value of a quantity corresponding to two adjacent marks on the SI scale.

Sensitivity threshold – the smallest value of change in a physical quantity, starting from which it can be measured by a given means. Sensitivity threshold in units of input quantity.

Measuring range – the range of values of a quantity within which the permissible limits of SI error are normalized. The quantities that limit the measurement range from below and above (left and right) are called respectively lower and upper measurement limit. The range of values of the instrument scale, limited by the initial and final values of the scale, is called range of indications.

Variation of indications – the greatest variation in the output signal of the device under constant external conditions. It is a consequence of friction and backlash in device components, mechanical and magnetic hysteresis of elements, etc.

Output Variation – this is the difference between the output signal values corresponding to the same actual input value when slowly approaching the selected input value from the left and right.

Dynamic characteristics, i.e., the characteristics of the inertial properties (elements) of the measuring device, which determine the dependence of the SI output signal on time-varying quantities: input signal parameters, external influencing quantities, load.

CLASSIFICATION OF ERRORS

The measurement procedure consists of the following stages: adopting a model of the measurement object, choosing a measurement method, choosing a measuring instrument, conducting an experiment to obtain the result. As a result, the measurement result differs from the true value of the measured value by a certain amount called error measurements. A measurement can be considered complete if the measured value is determined and the possible degree of its deviation from the true value is indicated.

According to the method of expressing the errors of measuring instruments, they are divided into absolute, relative and reduced.

Absolute error – SI error, expressed in units of the measured physical quantity:

Relative error – SI error, expressed as the ratio of the absolute error of the measuring instrument to the measurement result or to the actual value of the measured physical quantity:

For a measuring device, γrel characterizes the error at a given point on the scale, depends on the value of the measured quantity and has the smallest value at the end of the device scale.

Given error – relative error, expressed as the ratio of the absolute error of the SI to the conventionally accepted value of a quantity, constant over the entire measurement range or in part of the range:

where Xnorm is a normalizing value, i.e. some established value in relation to which the error is calculated. The standard value can be the upper limit of SI measurements, measurement range, scale length, etc.

Based on the reason and conditions for the occurrence of errors in measuring instruments, they are divided into basic and additional.

The main error is this is the error of SIs under normal operating conditions.

Additional error – component of the SI error that arises in addition to the main error as a result of the deviation of any of the influencing quantities from its normal value or as a result of its going beyond the normal range of values.

Limit of permissible basic error – the largest basic error at which an SI can be considered suitable and allowed for use according to technical conditions.

Limit of permissible additional error – This is the largest additional error at which the measuring instrument can be approved for use.

A generalized characteristic of this type of measuring instrument, usually reflecting the level of their accuracy, determined by the limits of permissible main and additional errors, as well as other characteristics affecting accuracy, is called accuracy class SI.

Systematic error – component of the error of a measuring instrument, taken as constant or naturally varying.

Random error – component of the SI error that varies randomly.

Misses – gross errors associated with operator errors or unaccounted external influences.

Depending on the value of the measured value, the SI errors are divided into additive, independent of the value of the input quantity X, and multiplicative, proportional to X.

Additive error Δadd does not depend on the sensitivity of the device and is constant in value for all values of the input quantity X within the measurement range. Example: zero error, discreteness (quantization) error in digital devices. If the device has only an additive error or it significantly exceeds other components, then the limit of the permissible main error is normalized in the form of a reduced error.

Multiplicative bias depends on the sensitivity of the device and changes in proportion to the current value of the input value. If the device has only a multiplicative error or it is significant, then the limit of the permissible relative error is expressed as a relative error. The accuracy class of such measuring instruments is indicated by one number placed in a circle and equal to the limit of permissible relative error.

Depending on the influence of the nature of the change in the measured value, SI errors are divided into static and dynamic.

Static errors – the error of the SI used in the measurement of a physical quantity taken to be constant.

Dynamic error – SI error that occurs when measuring a physical quantity that changes (during the measurement process), which is a consequence of the inertial properties of SI.

SYSTEMATIC ERRORS

According to the nature of the change, systematic errors are divided into constant (preserving magnitude and sign) and variable (changing according to a certain law).

Based on the reasons for their occurrence, systematic errors are divided into methodological, instrumental and subjective.

Methodological errors arise due to imperfection, incompleteness of the theoretical justification of the adopted measurement method, the use of simplifying assumptions and assumptions in the derivation of the applied formulas, due to the incorrect choice of measured quantities.

In most cases, methodological errors are systematic, and sometimes random (for example, when the coefficients of the working equations of a measurement method depend on measurement conditions that vary randomly).

Instrumental errors are determined by the properties of the measuring instruments used, their influence on the measurement object, technology and manufacturing quality.

Subjective errors are caused by the state of the operator carrying out the measurements, his position during work, the imperfection of the sensory organs, the ergonomic properties of the measuring instruments - all this affects the accuracy of sighting.

Detection of the causes and type of functional dependence makes it possible to compensate for the systematic error by introducing appropriate corrections (correction factors) into the measurement result.

RANDOM ERRORS

A complete description of a random variable, and therefore the error, is its distribution law, which determines the nature of the appearance of various results of individual measurements.

In the practice of electrical measurements, various distribution laws are encountered, some of which are discussed below.

Normal Law distributions (Gauss's law). This law is one of the most common laws of error distribution. This is explained by the fact that in many cases, measurement error is formed under the influence of a large set of different reasons independent of each other. Based on the central limit theorem of probability theory, the result of the action of these causes will be an error distributed according to the normal law, provided that none of these causes is significantly dominant.

The normal distribution law of errors is described by the formula

where ω(Δx) is the probability density of the error Δx; σ[Δx] - standard deviation of error; Δxc is the systematic component of the error.

The appearance of the normal law is shown in Fig. 1, and for two values of σ[Δx]. Because

Then the law of distribution of the random component of the error

has the same form (Figure 1,b) and is described by the expression

where is the standard deviation of the random component of the error; = σ [Δx]

Rice. 1. Normal distribution law of measurement error (a) and the random component of measurement error (b)

Thus, the distribution law of the error Δx differs from the distribution law of the random component of the error only by a shift along the abscissa axis by the value of the systematic component of the error Δxc.

From probability theory it is known that the area under the probability density curve characterizes the probability of an error occurring. From Fig. 1, b it is clear that the probability R the appearance of an error in the range ± at greater than at (the areas characterizing these probabilities are shaded). The total area under the distribution curve is always equal to 1, i.e. the total probability.

Taking this into account, it can be argued that errors whose absolute values exceed appear with a probability equal to 1 - R, which at is less than at . Consequently, the smaller , the less often large errors occur, the more accurately the measurements are made. Thus, the Standard Deviation can be used to characterize the accuracy of measurements:

Uniform distribution law. If the measurement error with equal probability can take any value that does not go beyond certain limits, then such an error is described by a uniform distribution law. In this case, the error probability density ω(Δx) is constant within these boundaries and equal to zero outside these boundaries. The uniform distribution law is shown in Fig. 2. Analytically it can be written like this:

For –Δx1 ≤ Δx ≤ + Δx1;

Figure 2. Uniform distribution law

This distribution law is in good agreement with the error from friction in the supports of electromechanical devices, the non-excluded remnants of systematic errors, and the discreteness error in digital devices.

Trapezoidal distribution law. This distribution is graphically depicted in Fig. 3, A. The error has such a distribution law if it is formed from two independent components, each of which has a uniform distribution law, but the width of the interval of uniform laws is different. For example, when two measuring transducers are connected in series, one of which has an error uniformly distributed in the interval ±Δx1, and the other has an error uniformly distributed in the interval ±Δx2, the total conversion error will be described by a trapezoidal distribution law.

Triangular distribution law (Simpson's law). This distribution (see Fig. 3, b) is a special case of trapezoidal, when the components have the same uniform distribution laws.

Bimodal distribution laws. In measurement practice, bimodal distribution laws are encountered, that is, distribution laws that have two maxima of the probability density. In the bimodal distribution law, which can be in devices that have an error from the backlash of kinematic mechanisms or from hysteresis when the magnetization reversal of device parts.

Fig.3. Trapezoidal (A) and triangular (b) distribution laws

Probabilistic approach to describing errors. Point estimates of distribution laws.

When, when carrying out repeated observations of the same thing with the same care and under the same conditions constant value we get results. differ from each other, this indicates the presence of random errors in them. Each such error arises due to the simultaneous influence of many random disturbances on the observation result and is itself a random variable. In this case, it is impossible to predict the result of an individual observation and correct it by introducing a correction. It can only be stated with a certain degree of confidence that the true value of the measured quantity is within the range of observational results from l>.m to Xn. ah, where htt. At<а - соответственно, нижняя и верхняя границы разброса. Однако остается неясным, какова вероятность появления того или ^иного значения погрешности, какое из множества лежащих в этой области значений величины принять за результат измерения и какими показателями охарактеризовать случайную погрешность результата. Для ответа на эти вопросы требуется принципиально иной, чем при анализе систематических погрешностей, подход. Подход этот основывается на рассмотрении результатов наблюдений, результатов измерений и случайных погрешностей как случайных величин. Методы теории вероятностен и математической статистики позволяют установить вероятностные (статистические) закономерности появления случайных погрешностей и на основании этих закономерностей дать количественные оценки результата измерения и его случайной погрешности

In practice, all measurement results and random errors are discrete quantities, i.e., quantities xi, the possible values of which are separable from each other and can be counted. When using discrete random variables, the problem arises of finding point estimates of the parameters of their distribution functions based on samples - a series of values xi taken by a random variable x in n independent experiments. The sample used must be representative(representative), that is, it should fairly well represent the proportions of the general population.

The parameter estimate is called point, if it is expressed in one number. The problem of finding point estimates is a special case of the statistical problem of finding estimates of the parameters of the distribution function of a random variable based on a sample. Unlike the parameters themselves, their point estimates are random variables, and their values depend on the volume of experimental data, and the law

distributions - from the distribution laws of the random variables themselves.

Point estimates can be consistent, unbiased, and efficient. Wealthy is an estimate that, as the sample size increases, tends in probability to the true value of a numerical characteristic. Unbiased is an estimate whose mathematical expectation is equal to the estimated numerical characteristic. Most effective consider the one of “several possible unbiased estimates that has the smallest variance. The requirement of unbiasedness is not always practical in practice, since an estimator with small bias and low variance may be preferable to an unbiased estimator with high variance. In practice, it is not always possible to satisfy all three of these requirements at the same time, but the choice of assessment should be preceded by its critical analysis from all of these points of view.

The most common method for obtaining estimates is the maximum likelihood method, which results in asymptotically unbiased and efficient estimates with an approximately normal distribution. Other methods include the methods of moments and least squares.

The point estimate of the MO of the measurement result is arithmetic mean measured quantity

For any distribution law, it is a consistent and unbiased estimate, as well as the most effective according to the least squares criterion.

Point estimate of variance, determined by the formula

is unbiased and wealthy.

The standard deviation of a random variable x is defined as the square root of the variance. Accordingly, its estimate can be found by taking the root of the variance estimate. However, this operation is a nonlinear procedure, leading to a bias in the estimate thus obtained. To correct the estimate of the standard deviation, a correction factor k(n) is introduced, depending on the number of observations n. It varies from

k(3) = 1.13 to k(∞) ≈ 1.03. Estimation of standard deviation

The obtained MO and MSD estimates are random variables. This manifests itself in the fact that when repeating a series of n observations, different estimates of and will be obtained each time. It is advisable to evaluate the dispersion of these estimates using the standard deviation Sx Sσ.

Estimation of the standard deviation of the arithmetic mean

Estimation of the standard deviation of the standard deviation

It follows that the relative error in determining the standard deviation can be

rated as

It depends only on the kurtosis and the number of observations in the sample and does not depend on the standard deviation, i.e., the accuracy with which the measurements are made. Due to the fact that a large number of measurements are carried out relatively rarely, the error in determining σ can be quite significant. In any case, it is larger than the error due to the bias in the estimate due to the extraction of the square root and is eliminated by the correction factor k(n). In this regard, in practice, they neglect to take into account the bias in the estimation of the standard deviation of individual observations and determine it using the formula

i.e., they consider k(n)=1.

Sometimes it is more convenient to use the following formulas to calculate estimates of the standard deviation of individual observations and the measurement result:

Point estimates of other distribution parameters are used much less frequently. Estimates of the coefficient of asymmetry and kurtosis are found using the formulas

The determination of the dispersion of estimates of the coefficient of skewness and kurtosis is described by various formulas depending on the type of distribution. A brief overview of these formulas is given in the literature.

Probabilistic approach to describing random errors.

Center and moments of distribution.

As a result of the measurement, the value of the measured quantity is obtained in the form of a number in accepted units of quantity. It is also convenient to express the measurement error as a number. However, the measurement error is a random variable, an exhaustive description of which can only be a distribution law. From probability theory it is known that the distribution law can be characterized by numerical characteristics (non-random numbers), which are used to quantify the error.

The main numerical characteristics of distribution laws are the mathematical expectation and dispersion, which are determined by the expressions:

Where M- symbol of mathematical expectation; D- dispersion symbol.

Mathematical expectation of error measurements is a non-random quantity around which other error values are scattered during repeated measurements. The mathematical expectation characterizes the systematic component of the measurement error, i.e. M [Δx]=ΔxC. As a numerical characteristic of error

M [Δx] indicates the bias of the measurement results relative to the true value of the measured value.

Error variance D [Δx] characterizes the degree of dispersion (scatter) of individual error values relative to the mathematical expectation. Since dispersion occurs due to the random component of the error, then .

The smaller the dispersion, the smaller the scatter, the more accurate the measurements are. Consequently, dispersion can serve as a characteristic of the accuracy of the measurements. However, variance is expressed in units of error squared. Therefore, as a numerical characteristic of measurement accuracy, they use standard deviation with a positive sign and expressed in error units.

Usually, when carrying out measurements, one strives to obtain a measurement result with an error not exceeding the permissible value. Knowing only the standard deviation does not allow one to find the maximum error that may occur during measurements, which indicates the limited capabilities of such a numerical characteristic of the error as σ[Δx] . Moreover, under different measurement conditions, when the distribution laws of errors may differ from each other, the error With a smaller dispersion can take on larger values.

The maximum error values depend not only on σ[Δx] , but also on the type of distribution law. When the error distribution is theoretically unlimited, for example under the normal distribution law, the error can be of any value. In this case, we can only talk about an interval beyond which the error will not go beyond some probability. This interval is called confidence interval, characterizing its probability - confidence probability, and the boundaries of this interval are the confidence values of the error.

In measurement practice, various confidence probability values are used, for example: 0.90; 0.95; 0.98; 0.99; 0.9973 and 0.999. The confidence interval and confidence probability are selected depending on the specific measurement conditions. So, for example, under the normal law of distribution of random errors with a standard deviation, a confidence interval from to is often used, for which the confidence probability is equal to

0.9973. This confidence probability means that on average, out of 370 random errors, only one error in absolute value will be

more. Since in practice the number of individual measurements rarely exceeds several tens, the appearance of even one random error greater than

An unlikely event, but the presence of two similar errors is almost impossible. This allows us to state with sufficient grounds that all possible random measurement errors, distributed according to the normal law, practically do not exceed the absolute value (the “three sigma” rule).

In accordance with GOST, the confidence interval is one of the main characteristics of measurement accuracy. This standard establishes one of the forms for presenting the measurement result in the following form: x; Δx from Δxн to Δxв1; R , where x - measurement result in units of the measured quantity; Δx, Δxн, Δxв - respectively, the measurement error with its lower and upper boundaries in the same units; R - the probability with which the measurement error is within these limits.

GOST allows other forms of presenting the measurement result, which differ from the given form in that they indicate separately the characteristics of the systematic and random components of the measurement error. In this case, for a systematic error, its probabilistic characteristics are indicated. It was noted earlier that sometimes systematic error has to be assessed from a probabilistic point of view. In this case, the main characteristics of the systematic error are M [Δхс], σ [Δхс] and its confidence interval. Isolating the systematic and random components of the error is advisable if the measurement result will be used in further data processing, for example, when determining the result of indirect measurements and assessing its accuracy, when summing up errors, etc.

Any form of presentation of a measurement result provided for by GOST must contain the necessary data on the basis of which a confidence interval for the error of the measurement result can be determined. In the general case, a confidence interval can be established if the type of error distribution law and the main numerical characteristics of this law are known.

________________________

1 Δxн and Δxв must be indicated with their own signs. In the general case |Δxн| may not be equal to |Δxв|. If the error boundaries are symmetrical, i.e. |Δxн| = |Δxв| = Δx, then the measurement result can be written as follows: x ±Δx; P.

ELECTROMECHANICAL DEVICES

An electromechanical device includes a measuring circuit, a measuring mechanism and a reading device.

Magnetoelectric devices.

Magnetoelectric devices consist of a magnetoelectric measuring mechanism with a reading device and a measuring circuit. These instruments are used to measure direct currents and voltages, resistances, the amount of electricity (ballistic galvanometers and coulometers), and also to measure or indicate small currents and voltages (galvanometers). In addition, magnetoelectric instruments are used to record electrical quantities (recording instruments and oscillographic galvanometers).

The torque in the measuring mechanism of a magnetoelectric device arises as a result of the interaction of the magnetic field of a permanent magnet and the magnetic field of the coil with current. Magnetoelectric mechanisms with a moving coil and a moving magnet are used. (most common with moving coil).

Advantages: high sensitivity, low intrinsic energy consumption, linear and stable nominal static conversion characteristic α=f(I), no influence of electric fields and little influence of magnetic fields (due to a fairly strong field in the air gap (0.2 - 1.2 T)) .

Disadvantages: low current overload capacity, relative complexity and high cost, react only to direct current.

Electrodynamic (ferrodynamic) devices.

Electrodynamic (ferrodynamic) devices consist of an electrodynamic (ferrodynamic) measuring mechanism with a reading device and a measuring circuit. These instruments are used to measure direct and alternating currents and voltages, power in direct and alternating current circuits, and the phase shift angle between alternating currents and voltages. Electrodynamic instruments are the most accurate electromechanical instruments for alternating current circuits.

Torque in electrodynamic and ferrodynamic measuring mechanisms arises as a result of the interaction of the magnetic fields of fixed and moving coils with currents.

Advantages: they operate on both direct and alternating current (up to 10 kHz) with high accuracy and high stability of their properties.

Disadvantages: electrodynamic measuring mechanisms have low sensitivity compared to magnetoelectric mechanisms. Therefore, they have a high inherent power consumption. Electrodynamic measuring mechanisms have a low current overload capacity, are relatively complex and expensive.

The ferrodynamic measuring mechanism differs from the electrodynamic mechanism in that its stationary coils have a magnetic core made of soft magnetic sheet material, which makes it possible to significantly increase the magnetic flux, and therefore the torque. However, the use of a ferromagnetic core leads to errors caused by its influence. At the same time, ferrodynamic measuring mechanisms are little affected by external magnetic fields.

Electromagnetic devices

Electromagnetic devices consist of an electromagnetic measuring mechanism with a reading device and a measuring circuit. They are used to measure alternating and direct currents and voltages, to measure frequency and phase shift between alternating current and voltage. Due to their relatively low cost and satisfactory performance, electromagnetic devices make up the majority of the total panel equipment fleet.

The torque in these mechanisms arises as a result of the interaction of one or more ferromagnetic cores of the moving part and the magnetic field of the coil through the winding of which current flows.

Advantages: simplicity of design and low cost, high operational reliability, ability to withstand large overloads, ability to operate in both direct and alternating current circuits (up to approximately 10 kHz).

Disadvantages: low accuracy and low sensitivity, strong influence on the operation of external magnetic fields.

Electrostatic devices.

The basis of electrostatic devices is an electrostatic measuring mechanism with a reading device. They are mainly used for measuring AC and DC voltages.

Torque in electrostatic mechanisms arises as a result of the interaction of two systems of charged conductors, one of which is movable.

Induction devices.

Induction devices consist of an induction measuring mechanism with a reading device and a measuring circuit.

The operating principle of induction measuring mechanisms is based on the interaction of magnetic fluxes of electromagnets and eddy currents induced by magnetic fluxes in a moving part made in the form of an aluminum disk. Currently, the most commonly used induction devices are electrical energy meters in alternating current circuits.

The deviation of the measurement result from the true value of the measured quantity is called measurement error. Measurement error Δx = x - xi, where x is the measured value; xi is the true value.

Since the true value is unknown, practically the measurement error is estimated based on the properties of the measuring instrument, the experimental conditions and the analysis of the results obtained. The obtained result differs from the true value, therefore the measurement result has value only if an estimate of the error of the obtained value of the measured quantity is given. Moreover, most often it is not the specific error of the result that is determined, but degree of unreliability- boundaries of the zone in which the error is located.

The concept is often used "measurement accuracy" - a concept reflecting the closeness of a measurement result to the true value of the measured quantity. High measurement accuracy corresponds to low measurement error.

IN Any of a given number of quantities can be chosen as the main ones, but in practice the quantities that can be reproduced and measured with the highest accuracy are chosen. In the field of electrical engineering, the main quantities are length, mass, time and electric current.

The dependence of each derivative quantity on the basic ones is reflected by its dimension. Dimension of quantity is a product of the designations of basic quantities raised to the appropriate powers, and is its qualitative characteristic. The dimensions of quantities are determined based on the corresponding equations of physics.

Physical quantity is dimensional, if its dimension includes at least one of the basic quantities raised to a power not equal to zero. Most physical quantities are dimensional. However, there are dimensionless(relative) quantities representing the ratio of a given physical quantities to the same name, used as the initial (reference) one. Dimensionless quantities are, for example, transformation ratio, attenuation, etc.

Physical quantities, depending on the variety of sizes that they can have when changing in a limited range, are divided into continuous (analog) and quantized (discrete) by size (level).

Analog value can have an infinite number of sizes within a given range. This is the overwhelming number of physical quantities (voltage, current, temperature, length, etc.). Quantized magnitude has only a countable set of sizes in a given range. An example of such a quantity would be a small electric charge, the size of which is determined by the number of electron charges included in it. The dimensions of a quantized quantity can only correspond to certain levels - quantization levels. The difference between two adjacent quantization levels is called quantization stage (quantum).

The value of an analogue quantity is determined by measurement with inevitable error. A quantized quantity can be determined by counting its quanta if they are constant.

Physical quantities can be constant or variable over time. When measuring a time-constant quantity, it is sufficient to determine one of its instantaneous values. Time-variable quantities can have a quasi-deterministic or random nature of change.

Quasi-deterministic physical quantity - a quantity for which the type of dependence on time is known, but the measured parameter of this dependence is unknown. Random physical quantity - a quantity whose size changes randomly over time. As a special case of time-varying quantities, we can distinguish discrete time quantities, that is, quantities whose sizes are different from zero only at certain times.

Physical quantities are divided into active and passive. Active quantities(for example, mechanical force, EMF of an electric current source) are capable of creating measurement information signals without auxiliary energy sources (see below). Passive quantities(for example, mass, electrical resistance, inductance) cannot themselves create measurement information signals. To do this, they need to be activated using auxiliary energy sources, for example, when measuring the resistance of a resistor, current must flow through it. Depending on the objects of study, they talk about electrical, magnetic or non-electric quantities.

A physical quantity that, by definition, is assigned a numerical value equal to one is called unit of physical quantity. The size of a unit of physical quantity can be any. However, measurements must be made in generally accepted units. The commonality of units on an international scale is established by international agreements. Units of physical quantities, according to which the International System of Units (SI) has been introduced into mandatory use in our country.

When studying an object of study, it is necessary to select physical quantities for measurements, taking into account the purpose of the measurement, which comes down to studying or assessing any properties of the object. Since real objects have an infinite number of properties, in order to obtain measurement results that are adequate for the purpose of measurement, certain properties of objects that are essential for the chosen purpose are selected as measured quantities, i.e., they are selected object model.

STANDARDIZATION

The State Standardization System (DSS) in Ukraine is regulated in the main standards for it:

DSTU 1.0 – 93 DSS. Basic provisions.

DSTU 1.2 – 93 DSS. The procedure for developing state (national) standards.

DSTU 1.3 – 93 DSS. The procedure for developing the construction, presentation, execution, coordination, approval, designation and registration of technical specifications.

DSTU 1.4 – 93 DSS. Enterprise standards. Basic provisions.

DSTU 1.5 – 93 DSS. Basic provisions for the construction, presentation, design and content of standards;

DSTU 1.6 – 93 DSS. The procedure for state registration of industry standards, standards of scientific, technical and engineering partnerships and communities (unions).

DSTU 1.7 – 93 DSS. Rules and methods for the adoption and application of international and regional standards.

Standardization bodies are:

Central executive body in the field of standardization DKTRSP

Standardization Council

Technical committees for standardization

Other entities involved in standardization.

Classification of regulatory documents and standards in force in Ukraine.

International normative documents, standards and recommendations.

State Standards of Ukraine.

Republican standards of the former Ukrainian SSR, approved before 08/01/91.

Instructional documents of Ukraine (KND and R)

State Classifiers of Ukraine (DK)

Industry standards and specifications of the former USSR, approved before 01/01/92 with extended validity periods.

Industry standards of Ukraine registered in UkrNDISSI

Specifications registered by territorial standardization bodies of Ukraine.

Metrology (from the Greek “Metron” - measure, measuring instrument and “Logos” - study) is the science of measurements, methods and means of ensuring their unity and ways to achieve the required accuracy. The subject of metrology is the extraction of quantitative information about the properties of objects with a given accuracy and reliability. The means of metrology is a set of measurements and metrological standards that provide the required accuracy.

Metrology consists of three sections: theoretical, applied, legislative.

Theoretical metrology deals with fundamental issues of measurement theory, the development of new measurement methods, the creation of systems of units of measurement and physical constants.

Applied metrology studies the practical application of the results of developments of theoretical and legal metrology in various fields of activity.

Legal metrology establishes mandatory legal, technical and legal requirements for the use of units of quantities, standards, reference materials, methods and measuring instruments, aimed at ensuring the uniformity and accuracy of measurements in the interests of society.

The subject of metrology is obtaining quantitative information about the properties of objects and processes with a given accuracy and reliability.

A physical quantity is one of the properties of an object (system, phenomenon, process), which can be distinguished among other properties and assessed (measured) in one way or another, including quantitatively. If the property of an object (phenomenon, process) is a qualitative category, since it characterizes distinctive features in its difference or commonality with other objects, then the concept of quantity serves to quantitatively describe one of the properties of this object. Quantities are divided into ideal and real, the latter of which are physical and non-physical.

A unit of physical quantity is a physical quantity of a fixed size, which is conventionally assigned a numerical value equal to 1, and is used for the quantitative expression of physical quantities similar to it.

The basic concept of metrology is measurement. Measurement is the determination of the value of a quantity experimentally using special technical means or, in other words, a set of operations performed to determine the quantitative value of a quantity.

The significance of measurements is expressed in three aspects: philosophical, scientific and technical.

The philosophical aspect is that measurements are the main means of objective knowledge of the surrounding world, the most important universal method of knowing physical phenomena and processes.

The scientific aspect of measurements is that with the help of measurements, the connection between theory and practice is carried out; without them, testing scientific hypotheses and the development of science are impossible.

The technical aspect of measurements is obtaining quantitative information about the object of management and control, without which it is impossible to ensure the conditions for carrying out the technological process, product quality and effective process control.

Unity of measurements is a state of measurements in which their results are expressed in legal units and errors are known with a given probability. Unity of measurements is necessary in order to be able to compare the results of measurements taken at different times, using different methods and measuring instruments, as well as in different geographical locations. The uniformity of measurements is ensured by their properties: the convergence of measurement results, the reproducibility of measurement results and the correctness of measurement results.

Convergence is the closeness of measurement results obtained by the same method, identical measuring instruments, and the proximity to zero of the random measurement error.

The reproducibility of measurement results is characterized by the closeness of measurement results obtained by different measuring instruments (of course the same accuracy) by different methods.

The correctness of measurement results is determined by the correctness of both the measurement techniques themselves and the correctness of their use in the measurement process, as well as the closeness to zero of the systematic measurement error.

The process of solving any measurement problem usually includes three stages: preparation, carrying out the measurement (experiment) and processing the results. In the process of carrying out the measurement itself, the measurement object and the measuring instrument are brought into interaction.

A measuring instrument is a technical device used in measurements and having standardized metrological characteristics.

The result of a measurement is the value of a physical quantity found by measuring it. During the measurement process, the measuring instrument, operator and measurement object are affected by various external factors called influencing physical quantities.

These physical quantities are not measured by measuring instruments, but they influence the measurement results. Imperfect manufacturing of measuring instruments, inaccuracy of their calibration, external factors (ambient temperature, air humidity, vibration, etc.), subjective operator errors and many other factors related to influencing physical quantities are inevitable causes of measurement error.

Measurement accuracy characterizes the quality of measurements, reflecting the closeness of their results to the true value of the measured value, i.e. close to zero measurement error.

Measurement error is the deviation of the measurement result from the true value of the measured value.

The true value of a physical quantity is understood as a value that would ideally reflect, in qualitative and quantitative terms, the corresponding properties of the measured object.

Basic postulates of metrology: the true value of a certain quantity exists and it is constant; the true value of the measured quantity cannot be found. It follows that the measurement result is mathematically related to the measured value through a probabilistic dependence.

Since the true value is the ideal value, the actual value is used as the closest one to it. The actual value of a physical quantity is the value of a physical quantity found experimentally and so close to the true value that it can be used instead. In practice, the arithmetic mean of the measured value is taken as the actual value.

Having considered the concept of measurements, one should distinguish between related terms: control, testing and diagnosis.

Control is a special case of measurement carried out to establish compliance of the measured value with specified limits.

Testing is the reproduction of certain influences in a given sequence, measurement of the parameters of the tested object and their registration.

Diagnosis is the process of recognizing the state of the elements of an object at a given time. Based on the results of measurements performed for parameters that change during operation, it is possible to predict the condition of the object for further operation.

Metrology - basic terms and definitions. Basic concepts and terms of metrology Metrological concepts

Metrology concept

Goals and objectives of metrology

Unity of measurements

Principles and methods of metrology

Measuring instruments

What is error?

Types of metrology by area of ​​application

Conclusion

Metrology

Goals and objectives of metrology

Axioms of metrology

Metrology terms and definitions

History of metrology

The formation and differences of metrology in the USSR (Russia) and abroad

Selected areas of metrology

1. Physical quantities

Influential fv

Basic terms and definitions metrology

1. Physical quantities

Influential fv

Basic terms and definitions in metrology

Basic terms and definitions metrology

1. Physical quantities

Influential fv

Metrology Basic terms and definitions

Preface

Introduction

What is metrology

Basic Concepts

General metrology

Industrial metrology

Legal metrology

Basics

Objects

Significance criteria

Goals

Tasks

Kinds

Direct and indirect measurements

Aggregate and joint measurements

Statistical

Multiple and single

Absolute and relative

Measurement scale

Conclusion

Types of metrology by area of application