Final report: Comparison of pressure standards in the range 0.8 MPa to 8 MPa (gas media, gauge mode)

Abstract

Comparison of pressure standards in the range 0.8 MPa to 8 MPa (gas media, gauge mode) Participants TR (T ÜB İTAK-UME), IT (CNR-IMGC) Organizing body Bilateral ResultsA comparison of the pressure standards of the T ÜB İTAK, Ulusal Metroloji Enstitüsü (UME), Turkey, and the Consiglio Nazionale delle Richerche, Istituto di Metrologia "G. Colonnetti" (CNR-IMGC), Italy, in the pressure range 0.8 MPa to 8 MPa in gas media and gauge mode took place at the T ÜB İTAK-UME in 1996. This work was carried out using two similar piston-cylinder units in tungsten carbide having a nominal effective area of 49 mm 2 , both units being oil-lubricated. The parameters to be measured were the effective area of the UME piston-cylinder assembly, expressed as the effective area at atmospheric pressure and 20 C, and its pressure distortion coefficient λ. Details of the pressure balances, measurement setup and procedures used by participants, together with an analysis of the results, are given in [1].For each measurement, the pressure of the UME system was calculated using the values determined in 1993 [2] for the effective area and the pressure distortion coefficient of the UME piston-cylinder assembly. The corresponding and λ values of the IMGC piston-cylinder unit had been determined by comparison against a national primary standard of the IMGC [3]. The relative pressure difference between the UME and IMGC systems was found to be between 5.8 10 -6 and 17.4 10 -6 . In all cases, the difference between the UME and IMGC pressures divided by the root-sum-square of their standard uncertainties was found to be much less than one. Thus, this comparison confirmed the agreement between the pressure scales of Italy (CNR-IMGC) and Turkey (T ÜB İTAK-UME) in gas media (gauge mode) from 0.8 MPa to 8 MPa, within the combined relative standard uncertainties of 11 10 -6 for the IMGC and 25 10 -6 for the UME [1]. Using these results, the effective area of the UME system was redetermined (see Table 1). The relative difference between the new (1996) value and the previous (1993) value used by the UME is 11.8 10 -6 . This comparison resulted in a reduction of the uncertainty of the effective area of the UME piston-cylinder assembly, from 40 10 -6 to 22.3 10 -6 ( = 2). Consequently, a reduction has also been achieved in the uncertainty of pressure measurements performed by the UME over the pressure range 0.8 MPa to 8 MPa; this uncertainty is now 23.1 10 -6 ( = 2). The effective area and the pressure distortion values obtained, along with their estimated uncertainties , are given in Table 1; all uncertainties are quoted at the = 2 level.Table 1. Results obtained on the effective area of the UME piston-cylinder assembly.