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Section 9. Technical sciences
Masharipov Shodlik Masharipovich, Miralieva Aziza Qayumovna, Raxmatullaev Sarvar Anvarovich, Fattoev Firuz Farhod Ugli, Onbashi Lenie Rustemovna, Tashkent State Technical University named after Islam Karimov E-mail: [email protected]
NORMALIZATION OF CHARACTERISTICS OF MEASUREMENT MEANS AND CLASSES OF ACCURACY OF MEASUREMENT MEANS
Abstract. The article discusses the valuation of the metrological characteristics of measuring instruments. The features of the definition and confirmation of the actual metrological characteristics of measuring instruments.
Keywords. measuring instruments, metrological characteristics of measuring instruments, error, normative document, methodology.
Obtain quantitative information about the objects and phenomena of the world around us is possible only by measurement.
During measurements, the value of a quantity is obtained (its quantitative estimate) in the form of a certain number of units taken for this quantity - a numerical value.
Quantities that can be quantified, i.e. can be measured, called measurable quantities.
The correctness of the value of a quantity obtained by measurement is characterized by the degree of its approximation to the true value of this quantity.
The true value of a quantity belongs to the category of absolute truth, therefore in practice it is replaced with a real value.
Each practical dimension is subject to a specific goal, the error in the measurement is its error.
The accuracy of each measurement in technical and economic terms must be consistent with the purpose of the measurement itself.
Types, methods and methods of measurement are objects of consideration of theoretical and applied metrology and are selected in accordance with a specific measurement task.
The measurement error, and hence its instrumental component, must correspond to the purpose of the measurement. For this, a prerequisite is a preliminary calculation of the determination of the possible measurement error of a given value, by this measuring instrument under the specified conditions. The solution of this task is possible only if there is information on the limits of permissible values of all metrological characteristics of the measuring instrument. Therefore, the metrological characteristics of measuring instruments are subject to standardization - the establishment in regulatory documents
of measuring instruments of nominal values and the limits of permissible deviations of the real metrological characteristics of measuring instruments from their nominal values.
Along with the characteristics of the errors of measuring instruments, the following are subject to rationing: characteristics intended to determine the results of measurements;
sensitivity characteristics of measuring instruments to changes in operating conditions;
characteristics that determine the response of measuring instruments to a change in the measured value in the measurement process (dynamic characteristics);
characteristics that determine the interaction of measuring instruments with the object of measurement and the connection to the output of the measuring instrument of any components.
In addition to the normal conditions for measuring instruments, the operating conditions of application are normalized - the intervals of values of the influencing quantities, within which the errors of the measuring instrument are normalized.
The use of measuring instruments in conditions other
than operating conditions is unacceptable.
General requirements for standardized metrological characteristics of measuring instruments are set forth in GOST 8.009.
Technical means used in measurements and not having standardized metrological characteristics do not belong to measuring instruments.
When calculating the estimated error of measuring instruments under actual operating conditions, according to their normalized metrological characteristics, it is necessary to take into account all the relevant errors for these measuring tasks that constitute the errors of these tools.
NORMALIZATION OF CHARACTERISTICS OF MEASUREMENT MEANS AND CLASSES OF ACCURACY OF MEASUREMENT MEANS
In order to rationalize the choice of measuring instruments for solving specific measuring tasks, the form for expressing limits of permissible basic and additional errors of measuring instruments when standardizing them is selected taking into account the design features, principle of operation, conditions of use and purpose of measuring instruments and depending on the nature of the variation of errors within the measuring range.
For a qualitative comparison among themselves of measuring instruments of the same type, that is, the same accuracy class for measuring the same value and having different limits of permissible errors, the concept of accuracy class is used.
The accuracy class of measuring instruments is a generalized characteristic of this type of measuring instrument, reflecting their level of accuracy, determined by the limits of permissible basic and additional errors, as well as other characteristics affecting accuracy.
It should be noted that the accuracy class of measuring instruments, representing an indicator of their level of accuracy, is not a direct characteristic of the accuracy of measurements performed using these means. As mentioned above, the measurement error depends on a number of factors, including the measurement instrument error. The error of measuring instruments, in turn, depends on the influencing quantities, which in actual operating conditions can be combined in various ways.
Therefore, the accuracy class should be considered only as a symbol characterizing the error of measuring instruments, and not absolutize this concept. For example, the use of a measuring instrument of accuracy class 1.5 does not mean that the measurement error of this device will not exceed 1.5%.
Accuracy classes of measuring instruments are established in standards or technical conditions containing technical requirements for measuring instruments, divided by accuracy.
The designations of accuracy classes are applied directly to the measuring instruments and are indicated in the technical documentation on the measuring instruments.
To facilitate the selection of measuring instruments, the designation of accuracy classes is determined by the form of expressing the limits of the permissible basic and additional errors of measuring instruments.
The basic requirements for the forms of expression of the limits of permissible errors of measuring instruments and the designations of their accuracy classes are given in GOST 8.401.
Depending on the nature of the manifestation, systematic and random components of the error of the measuring instrument are distinguished; each of these components, depending on the form of the numerical expression, can be represented as an absolute or relative error.
The errors of measuring instruments depend on the conditions of their operation, so they are usually divided into the main and additional ones.
The metrological characteristics of measuring instruments are subject to standardization - the establishment in regulatory documents of measuring instruments of nominal values and the limits of permissible deviations of the real metrological characteristics of measuring instruments from their nominal values.
For each tool normalized and (or) working conditions of operation.
The use of measuring instruments in conditions other
than operating conditions is unacceptable.
Technical means used in measurements and not having standardized metrological characteristics do not belong to measuring instruments.
When calculating the estimated error of measuring instruments under actual operating conditions, according to their normalized metrological characteristics, it is necessary to take into account all the relevant errors for these measuring tasks that constitute the errors of these tools.
The accuracy class of measuring instruments is a generalized characteristic of this type of measuring instrument, reflecting the level of their accuracy.
Accuracy class should be considered only as a symbol characterizing the error of measuring instruments.
References:
1. Friedman A. E. Fundamentals of metrology. Modern course.- S. Pb.: NPO Professional, 2008.- 284 p.
2. Pronkin N. S. Fundamentals of Metrology: Workshop on Metrology and Measurements: study guide for universities.- M.: Logos: University Book, 2007.- 392 p.
3. Nedorezkov E. K. Methods of processing the results of measurement of physical quantities: Lecture notes.- Gorno-Altaisk: GAGU, 2011.- 208 p.
4. Khamkhanova D. N. Applied Metrology: Tutorial.-Ulan-Ude: Izv-vo ESTU, 2006.- 160 p.
