Alternative Evaluation of Key Comparisons Results of the AC-DC Voltage Transfer Difference Standards

Laboratories accredited by national accreditation bodies often use the calibration services of National Metrology Institutes. Those institutes are widely involved in key comparisons of its standards and have Calibration and Measurement Capabilities. These capabilities are published in the Key Comparison Database of the International Bureau of Measures and Weights based on key comparison results. Traditionally, key comparisons results are expressed in terms of the Degree of Equivalence of the National Metrology Institute standard with the its expanded uncertainty. In this case, no other characteristics are applied to evaluate of Calibration and Measurement Capabilities. This may make it difficult to select a calibration service for a specific National Metrology Institute by accredited laboratories. The paper presents the proposed alternative evaluation of key comparison results, which simplifies the analysis of National Metrology Institute calibration services in the presence of key comparison results with a number of comparison points. It provides for the use of the results obtained from key comparison of the E_n index as a criterion of data consistency. The practical application of the alternative evaluation for key comparison results for AC-DC voltage transfer difference is considered.