CCM key comparison in the pressure range 0.05 MPa to 1 MPa (gas medium, gauge mode). Phase A1: Dimensional measurements and calculation of effective area

Abstract

The results obtained by five laboratories in the determination from dimensional measurements of the effective areas of two gas-operated 10 cm2 piston-cylinder assemblies are presented. These measurements were carried out as phase A1 of a key comparison in the pressure range 0.05 MPa to 1 MPa under the auspices of the Consultative Committee for Mass and Related Quantities (CCM) of the Comité International des Poids et Mesures. The participants performed diameter, straightness and roundness measurements on each piston and cylinder bore and calculated the effective area of each piston-cylinder assembly using their own methods. The differences between diameters determined by the institutes are systematic and often greater than the uncertainties claimed by the participants. Nevertheless, all calculated effective areas agree with the reference values determined within the expanded uncertainties with a coverage factor 2, most of them even within their standard uncertainties. The choice of calculation method seems to be less important than the dimensional data themselves. The effective areas determined from the dimensional measurements are compared with those obtained in cross-float experiments with national pressure standards, in a comparison referred to as phase A2 and reported in a separate paper.