Many factories, factories and other industrial facilities have led to the need to tighten the supervision of instrumentation that are installed at such facilities. It is important to monitor the operability of these devices, however, monitoring of the metrological characteristics of the monitoring means is also necessary, since it is these numbers that will give the most complete information about the operability of the industrial complex.
General information
Since the topic is quite difficult to master, it is best to start with an explanation of what it is.
Metrological characteristics of measuring instruments is an expression of indicators of the metrological properties of these instruments by means of the numbers displayed on the screen. In addition, the effect will extend to the accuracy of the devices. There is a small classification of data on the metrological properties of measurement devices:
- Parameters that affect the location of the installation and further use of a particular device.
- Parameters that determine precision and indicate the accuracy of the results.
Metrological properties of measuring instruments are those factors that can have a direct impact on the result of those measurements that are carried out by these devices. In addition, the effect will extend to the error of the instruments.
The first group can be divided into two factors, which are decisive. The first is the measuring range of the device, and the second is the sensitivity threshold. However, most devices have another factor that is not very pleasant, but it is almost impossible to get rid of it - these are errors of measuring instruments.
Rationing of devices and measurement error
Understanding such terms as rationing and error is best done together, since without one of them there would have been no other. In simple words, norming is the regulated limits of deviations of the values of real metrological characteristics from their nominal value.
The process of standardization of devices was created so that it was possible to combine many devices into classes, as well as create interchangeability between them. During operation, it may happen that after normalizing metrological characteristics, one or more can go beyond the limits that are set. This indicates that the device is out of order, and it should be immediately adjusted or replaced with a working one.
Errors in metrological characteristics is the value of the difference that arose after measuring any working medium, between the value that the device shows and the value that is actually observed in the working environment. Simply put, this is the difference between the nominal value and what the device showed.
GOST errors
Since the state body closely monitors the quality of measuring devices, GOST was introduced, which clearly prescribes what characteristics of errors of the measuring device:
- The most important factor is the error rate of the measurement device.
- Also a very important indicator is the random part, which makes up the overall error for any device.
- Another important factor is taking into account the mean square deviation of that random part, which is included in the total error of any SI during measurement.
- It is necessary to take into account not only various random components and general errors of measuring instruments, but also such functions as autocorrelation.
Characteristics of measuring instruments (SI)
Since the operation of measuring instruments is also carried out at facilities with increased danger, all control parameters and other characteristics are regulated by certain state bodies, which, in turn, divided all the characteristics into several groups.
Main metrological characteristics:
- The first group is the parameters that are used to determine the measurement results. These include the scale division price, scale division length, measurement range, measurement limits, sensitivity, etc.
- The second group is the parameters of the sensitivity of measuring instruments to influencing factors. They mean those whose changes can lead to incorrect indicators on the device.
- The metrological characteristics of measuring instruments include dynamic parameters that reflect the inertial properties of SI. They appear when various parameters affecting the device change their parameters over time.
GOST metrological characteristics
The State Control Service published GOST 8.009-84, which established the nomenclature of metrological characteristics (MX). Also, this document regulates clear rules that should be followed when choosing different standardized for NMH. These rules apply to some measurement devices.
In addition, the procedures were established by which it is necessary to select methods for normalizing the MX parameters, and then enter them into the scientific and technical documentation. In addition to this, this document introduced clear rules that every measuring instrument must comply with from a technical point of view.
In addition, in this GOST there is a provision that states that it is allowed to normalize metrological characteristics that are not regulated in the decree. However, it is allowed to do this only with the agreement of the State Standard, and also only if, due to the properties of the measuring instrument, its MX cannot be determined according to the standards that were given in GOST.
There are also exceptions to which this decree does not apply - these are reference instruments, calibration facilities and measuring instruments that were developed as exemplary specimens.
General provisions of GOST
- The metrological characteristics of measuring instruments that were installed as standard are the source information about the device.
- This initial information will be used to determine the measurement results, as well as for the estimated assessment of the characteristics.
- It will also be used to calculate the metrological characteristics and channels of measuring systems, which will consist of devices whose value will lend itself to normalization.
- Naturally, the initial information will be used in order to optimally select the place of use for each individual measuring instrument.
- Another provision that relates to a normative and technical document: in NTD it is necessary to normalize metrological characteristics that are established by the same standard and, if necessary, additionally normalize those characteristics that are necessary for the operation of the device and are specific.
MX nomenclature
In addition to general provisions, Gosstandart also established a general nomenclature of metrological characteristics:
- Parameters that are designed to determine the measurement results (without any corrections).
- The nomenclature for the conversion function of the measuring transducer or measuring device was also established if the scale does not have a name or its calibration is carried out in different units from those available for the input quantity - f (x).
- The nomenclature was established for a single-valued or multi-valued measure Y.
- The nomenclature for the type of output code, for the number of bits of the code, for the unit price of the smallest bit of code of measuring instruments, which are intended to produce results in digital form.
- A nomenclature was also established for the price of dividing the scale of the measuring device or its multi-valued measure.
State Metrology Service
In order to carry out activities to monitor all currently operating measuring devices, there is a civil service of the Russian Federation. It is worth saying that this organization is not a single body, but consists of several smaller organizations. The metrological organization includes state metrological services, the purpose of which is the control and management of measuring activities, as well as providing a single table of measurements for each parameter.
The main management of this state organization is located in such a government body as the Federal Agency. However, this service monitors the overall work of the entire structure, while there is a metrological department, which is considered the main one, but it is also part of the federal organization.
Functions of the governing body
In accordance with the law, which prescribes to establish the uniformity of measurements throughout the territory, the state metrological service was assigned such functions as:
- Coordinate activities in order to ensure uniformity of measurement between different regions and industries.
- Establish rules for the development and storage and operation of units of measure.
- Determine the general metrological requirements for measuring instruments, methods, as well as the results obtained after measurements.
- To carry out state metrological control over devices.
- Monitor compliance with international agreements on the recognition of test results, as well as verification of measuring instruments .
- Participate in various international organizations that provide unity in units of measure.
- To approve regulatory documents that are created to ensure uniformity of measurement.
HMS composition
It is worth saying that the GMS includes many other various organizations. For example:
- 7 scientific metrological state centers.
- VNIIMS, as well as about 100 other various centers for standardization and metrology.
The largest scientific centers, which possess the necessary number of specialists and equipment, are holders of state standards. That is, those devices on which all the others are equal. In addition, these institutes and research centers are engaged in research on measurement theory, on the development of scientific and methodological foundations of measurements, etc. The activities of these and other organizations are regulated by the Federal Agency for Technical Regulation and Metrology.
Industry Management Principles
In order to manage the metrological activities in various government sectors, the state has created separate organizations, which are called metrological services.
The main person in such devices was the chief metrologist. And in the industries themselves, smaller offices were introduced, which conducted their metrological activities. If we talk about smaller scales, then at each industrial facility separate services were introduced, responsible for the calibration and adjustment of measuring equipment, as well as for its verification.
The state obliged to create such small organizations in their enterprises for all whose activities by one side or another affect the use of measuring devices for supervision and control.
Metrological Service Structure
It is worth saying that the structure of such a service is determined by the standard provision and has the following form:
- The first and main metrology service located in the central office of the industry.
- Next are the metrological services related to the base.
- The last are the smallest services that are tied directly to an enterprise or organization within this industry.
The main tasks that are set for metrological services are quite simple and understandable. These state bodies must ensure the uniformity of measurement, increase the level of metrological support of industry and carry out metrological control and supervision of each measuring instrument.