Calculation of Effective Area for the NIM Primary Pressure Standards

摘要

The primary pressure standards of the National Institute of Metrology (NIM) are a group of five oil-operated piston-cylinder assemblies of 1 cm~(2) nominal cross-sectional area for the 10 MPa range. The five piston-cylinder assemblies were accurately dimensioned by the length division of NIM, including straightness, roundness and diameter measurements. Based on the dimensional data, the effective areas were calculated with relative standard uncertainties ranged from 5.7 centre dot 10~(-6) to 11 centre dot 10~(-6) using the Dadson's theory. We also carried out the cross-float measurements between each two of the piston-cylinder assemblies, and the effective area ratios were determined with relative standard uncertainties of about 9 centre dot 10~(-6). Finally, the effective areas of the five piston-cylinder assemblies were determined taking into account the results of both dimensional characterization and cross-float experiments using generalized least-squares method.