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Calibration and Measurement Capabilities (CMCs) of NMIs in light of the new revised GUM

The statement about the Calibration and Measurement Capability – CMC of the National Metrology Institutes is the result of the MRA (Mutual Recognition Arrangement) comparative measurements. The measurement capability of the laboratory is stated by the lowest measurement uncertainty which the laboratory can achieve in calibration or measurement. In this manner, the evaluation and expression of measurement uncertainty is implemented in accordance with the Guide to the Expression of Uncertainty in Measurement - GUM. With minor changes the GUM is now applicable to a wide range of measurements. Significant revisions of the GUM were proposed in 2015 and include the adoption of the Bayesian approach to the calculation of Type A and Type B evaluations of uncertainty and to the application of the Monte Carlo simulation. The novelty is that the coverage interval is calculated directly from the probability density function of the output quantity y and no longer depends on the effective number of degrees of freedom. The degrees of freedom associated with the Type A evaluation of uncertainty are no longer a measure of reliability, and the Type B evaluation of uncertainty is no longer joined by degrees of freedom. The proposed changes to the revised GUM contribute to an increasing amount of measurement uncertainty. In light of all of the above it will be necessary to revise the declared CMCs of Metrology Institutes.

Calibration and Measurement Capability – CMC; Measurement uncertainty; Revised GUM

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