Final report on key comparison CCM.P-K4 of absolute pressure standards from 1 Pa to 1000 Pa
This report describes a CCM key comparison of low absolute-pressure standards at seven National Metrology Institutes (NMIs) that was carried out during the period March 1998 to September 1999 in order to determine their degrees of equivalence at pressures in the range 1 Pa to 1000 Pa. The primary standards, which represent two principal measurement methods, included five liquid-column manometers and four static expansion systems. The transfer standard package consisted of four high-precision
... r high-precision pressure transducers, two capacitance diaphragm gauges to provide high resolution at low pressures, and two resonant silicon gauges to provide the required calibration stability. Two nominally identical transfer packages were used to reduce the time required for the measurements, with Package A being circulated among laboratories in the European region (IMGC, NPL-UK, and PTB) and Package B being circulated among laboratories in the Asia-Pacific region (CSIRO, KRISS, and NPL-I). The results obtained with different transfer packages were normalized by using data obtained from simultaneous calibrations of the two packages at the pilot laboratory (NIST). The degrees of equivalence of the measurement standards were determined in two ways, deviations from key comparison reference values and pairwise differences between these deviations. Apart from results from one NMI that were identified as outliers, the absolute pressure standards of the seven participating NMIs were generally found to be equivalent and the results revealed no significant relative bias between the two principal methods tested by this comparison.