The accuracy of measuring instruments, or rather, its value, is of no small importance, especially when it comes to measuring the smallest fluctuations or weighing very small scales. High-precision instruments are needed when weighing chemicals or precious metals, when measuring electrical voltage, the concentration of impurities in solutions or gases, fixing pressure or temperature fluctuations.
All measuring instruments, whether they are mechanical or electrical, regardless of the principle of their operation, are divided into several categories. The main metrological characteristic of devices and instruments for carrying out measurements of various kinds is the accuracy class, which determines the maximum error allowed during measurements. It is worth noting that the accuracy class shows only the probable deviations of the device from its own scale, however, it cannot testify to the accuracy of measurements made using the device.
Depending on the type of device, its accuracy class is determined. Let's look at this with examples. So, for devices with an arrow scale, the accuracy class will be indicated by a number that will display the magnitude of the error whenmeasurements. In this case, the number 2, 0 in the designation of the class will tell the specialist that the error is 2% of the value of his scale.
The number enclosed in a circle will indicate that this error value is a constant for any value on the scale of the device. The error in the form of a fraction will mean the amount of measurement inaccuracy in the maximum and minimum dimensions. The accuracy class can be indicated by a numeral (Arabic or Roman), a letter, or a numeral with the addition of a specific character or letter. So, for example, the accuracy class of the scales will be indicated by a number and a letter. For example, 0a or 2b.
The accuracy class of instruments must be indicated on the scale. The absence of such a designation also has a certain semantic load. The absence of error indications that can be obtained as a result of measurements indicates that this figure for a particular device exceeds 4%, it is considered out-of-class. For high-precision measurements, necessary, for example, in laboratory studies, devices are used, the error value of which ranges from 0.05-0.5. Such devices are usually called precision. Devices with an accuracy class above 1, 0 are technical means and are used in those areas where some inaccuracy is not critical.
The division of devices into classes depending on the magnitude of the error is regulated by the state standard, which clearly states for which device of which category it is permissibleone error or another. Testing of measuring instruments is initially carried out at the factory. Since during operation the error, as well as the accuracy of measurements, may lose its original values, all measuring instruments are regularly verified in specialized metrology centers. During this process, the readings and measurement values are compared with the reference values, after which the necessary correction is made.
