Evaluation of the measurement uncertainty during the calibration of metal reference gauges of the 2 nd category

The paper considers problematic issues related to ensuring the uniformity of measurements in the field of legal metrology, namely, during the calibration of working measurement standards used for verification of legally regulated measuring instruments. One of the conditions for ensuring the uniformity of measurements is the compliance of any measuring instrument with the requirements that are prescribed in its technical specification, where standardized metrological characteristics are indicated, which allows us to conclude about the suitability of the instrument for measurements in a known range and with a known accuracy. The procedure for verification of legally regulated measuring instruments establishes a ratio between the expanded measurement uncertainty provided for by the measurement standard and the maximum permissible error of the measuring instruments of no more than one to three. Determining such a ratio is an example of indirect accounting for the measurement uncertainty. The reliability of the assessment of the compliance of a working measurement standard with metrological requirements, which are regulated by the technical specification, depends on the correctness of the procedures for evaluating the measurement uncertainty during calibrations. The paper indicates the problems of updating the existing regulatory framework for the calibration of measuring instruments using reference gauges as an example and ensuring metrological traceability of the results of the calibration of the liquid volume measuring equipment. Attention was drawn to the need to apply in Ukraine the international practice of the standardization of calibration techniques and methods of uncertainty evaluation to ensure the uniformity of measurements. A procedure for evaluating the measurement uncertainty during the calibration of the reference 2 nd-grade gauge by the volumetric method, which is used as a working measurement standard when verifying legally regulated measuring instruments - fuel dispensers for refuelling cars - is proposed.