CIPM MRA COMPARISON REPORTS

This key comparison on gauge block was organized by APMP and piloted by KRISS. The artefacts consisted of both short and long gauge blocks with nominal lengths ranging from 0.5 mm to 500 mm.
For the short gauge blocks, steel and tungsten carbide gauge blocks of grade K with nominal lengths of 0.5 mm, 2 mm, 2.5 mm, 3 mm, 5 mm, 10 mm, 20 mm, 75 mm, and 100 mm were circulated. The measurement method for these blocks was restricted to optical interferometry.
For the long gauge blocks, two steel gauge blocks with nominal lengths of 400 mm and 500 mm were circulated, and each laboratory was allowed to use the measurement method in its laboratory that provided the smallest measurement uncertainty.
The measurand was the deviation of the central length from the nominal length of each gauge block, obtained as the arithmetic mean of the two values measured with the gauge block wrung on both measuring faces.
The measurement uncertainty was evaluated in accordance with the ISO Guide to the Expression of Uncertainty in Measurement (GUM), and both the uncertainty value and the uncertainty equation were reported.
The key comparison reference value (KCRV) was calculated on a gauge-by-gauge basis as the weighted mean of the participants' measurement results. For the long gauge blocks, which exhibited temporal drift, the KCRV was determined as a function of time.
The consistency of the comparison results with their associated uncertainties was assessed using the Birge ratio. The degrees of equivalence for each laboratory and each gauge block with respect to the KCRV were evaluated using E _n values. Possible correlations between results were considered, but no significant correlations were identified.
The measurement results of all participants for the 18 short gauge blocks were consistent, and all E _n values had magnitudes less than 1. For the long gauge blocks, however, the magnitudes of the E _n values for four laboratories (out of ten) exceeded 1, and two of these results were excluded from the determination of the KCRV for the long gauge blocks.

Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.

The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).