Final Report on the Key Comparison CCM.P-K4.2012 in Absolute Pressure from 1 Pa to 10 kPa.

The report summarizes the Consultative Committee for Mass (CCM) key comparison CCM.P-K4.2012 for absolute pressure spanning the range of 1 Pa to 10 000 Pa. The comparison was carried out at six National Metrology Institutes (NMIs), including National Institute of Standards and Technology (NIST), Physikalisch-Technische Bundesanstalt (PTB), Czech Metrology Institute (CMI), National Metrology Institute of Japan (NMIJ), Centro Nacional de Metrología (CENAM), and DI Mendeleyev Institute for Metrology (VNIIM). The comparison was made via a calibrated transfer standard measured at each of the NMIs facilities using their laboratory standard during the period May 2012 to September 2013. The transfer package constructed for this comparison preformed as designed and provided a stable artifact to compare laboratory standards. Overall the participants were found to be statistically equivalent to the key comparison reference value.

Precise determination of the pressure distortion coefficient of new controlled-clearance piston-cylinders based on the Heydemann-Welch model.

A new controlled-clearance (CC) pressure balance has been developed with the aim of improving hydraulic pressure standards up to pressures of 1 GPa. The pressure balance is equipped with a weight-loading unit that can load/unload selected weights automatically and a CC piston-cylinder that is designed for the jacket pressure to be applied independently. In this paper, the effective area A(e) of two kinds of the CC piston-cylinders for pressures of 200 and 500 MPa was examined based on the Heydemann-Welch model. The two parameters in the model, the jacket pressure coefficient and the zero clearance jacket pressure, were precisely determined by the characterization experiments, after which the pressure dependence of A(e) and its uncertainty were estimated. The uncertainty due to the pressure dependence of A(e) for the 500 MPa CC piston-cylinder was less than 7.5x10(-8) MPa(-1). To confirm the consistency of the estimations, the results of the two CC piston-cylinders were compared through a free-deformation (FD) piston-cylinder; the two estimations were in agreement with each other. Moreover, it was shown that the extent of nonlinearity in the pressure dependence of A(e) of the FD piston-cylinder can be evaluated by calibration against the CC piston-cylinder.