Realization of a national practical pressure scale for pressures up to 500 MPa

Abstract

The successful realization at the National Physical Laboratory of India of the national practical pressure scale up to 500 MPa is described. A brief account is given of the metrological characterization of the controlled-clearance piston gauge (CCPG) used as the national primary pressure standard up to 500 MPa. The measured pressure with a definite uncertainty budget has been used to determine the effective area, A0, at atmospheric pressure at a reference temperature of 23 °C and the pressure distortion coefficient, λ, of the four different piston-cylinder assemblies used as national secondary pressure standards. Emphasis is laid on the establishment of the pyramid structure of the traceability hierarchy according to the International Organization for Standardization (ISO) and European Co-operation for Accreditation (EA) guidelines for the expression of the uncertainty of measurement in calibration. The metrological data obtained were found to be within the limits of the uncertainty budgets of international key comparisons and bilateral comparison measurements.