Pressure comparison measurements between the CMI and the PTB in the range 0.07 MPa to 0.4 MPa

This report describes pressure comparison measurements in the range 0.07 MPa to 0.4 MPa between the Czech Institute of Metrology (CMI) and the Physikalisch-Technische Bundesanstalt (PTB) in the period 9 to 13 March 1998 at the Pressure Section of the PTB, Braunschweig. The transfer standard used was a gas-operated piston-cylinder assembly with a ceramic piston of nominal effective area 10 cm2 and a tungsten-carbide cylinder, installed in a pressure balance base unit, model PG 7601, manufactured by DH Instruments, USA. The measurements compare the effective area of the transfer piston-cylinder assembly as determined from dimensional data at the CMI with effective area data obtained from pressure measurements (i) in gauge mode with the primary standard pressure balance and (ii) in absolute and gauge mode with the primary standard dual-cistern mercury manometer of the PTB. Both primary standard instruments have been used in the international comparison measurements organized by the Consultative Committee for Mass and Related Quantites (CCM) of the Comite International des Poids et Mesures. It may be seen that geometrical measurement values of the effective area is minimal: for the standard pressure balance, 3.4 × 10-6 for absolute pressure, 3.4 × 10-6 for gauge pressure; and for the dual-cistern mercury manometer, 1.8 × 10-6 for gauge mode. The relative difference between the experimetnal absolute and gauge mode for the dual-cistern mercury manometer is 1.5 × 10-6.