Verification of the Indicating Measuring Instruments

What is it about?

The specific features of the measuring instruments verification based on the results of their calibration are considered. It is noted that, in contrast to the verification procedure used in the legal metrology, the verification procedure for calibrated measuring instruments has to take into account the uncertainty of measurements into account. In this regard, a large number of measuring instruments, considered as those that are in compliance after verification in the legal metrology, turns out to be not in compliance after calibration. In this case, it is necessary to evaluate the probability of compliance of indicating measuring instruments. The procedure of compliance probability determination on the basis of the Monte Carlo method is considered. An example of calibration of a Vernier caliper is given.

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Why is it important?

The items 5.6.2.1.1 and 5.10.4.1.b of ISO 17025:2005 prescribe that calibration certificates for measuring instruments (МIs) shall contain “the measurement results, including the measurement uncertainty and/or a statement of compliance with an identified metrological specification”. From this requirement, it follows that the presence of an indication of conformity of the calibrated MI to the established metrological requirements or separate metrological characteristics is necessary in the calibration certificate. The conformity assessment of the gauge according to the specified requirements is considered in a number of documents. The main requirement of these documents is the need to take into account the uncertainty of measurement when performing conformity assessment.

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