Six European metrological institutes compared their calculation methods, and estimated uncertainties, resulting in the derivation of the effective area A 0 (20˚C, p atm) of six piston-cylinder assemblies routinely in use in pressure balances that are primary standards of the pressure laboratories, operating in different pressure ranges in gas (up to 1 MPa) and in liquid (up to 1 GPa). The results for A 0 and its standard uncertainty u(A 0) are presented and compared.

After the CCM Medium Pressure Working Group intercomparison indicated that the SMU primary mercury manometer differed by more than 20 ppm from other national standards, attention was paid to determining and eliminating the possible sources of these deviations. These efforts included replacing or redesigning some of the manometer components. The modified manometer design is presented in this paper. A piston gauge has been calibrated in the absolute mode using nitrogen as a pressure media, with the primary standard manometers at four national standards laboratories: Slovensky' Metrologicky' Ustav (SMU), Bratislava; Amt fir Standardisierung, Messwesen und Warenpriifung (ASMW), Berlin; Physikalisch-Technische Bundesanstalt (PTB), Braunschweig; and the National Institute of Standards and Technology (NIST), Gaithersburg; over a period of six years. Each of these manometers is of a different design. This has provided a basis from which to determine how the design changes affect the SMU manometer performance. The results indicate that the previous systematic deviations have been eliminated in the upper pressure ranges. The results for all four manometers agree to within their claimed uncertainties, however at the lowest pressures significant differences still exist and require further investigation.

The regional key comparison EURAMET.M.P-K13 for pressure measurements in liquid media from 50 MPa to 500 MPa was piloted by the TÜBİTAK UME Pressure Group Laboratories, Turkey. The transfer standard was a DH-Budenberg pressure balance with a free deformation piston-cylinder unit of 2 mm 2 nominal effective area.

A EURAMET key comparison of the national pressure standards in the range 0.7 MPa to 7.0 MPa of gas gauge pressure was carried out. The circulation of the transfer standard began in November 2011 and lasted until November 2016. The measurand of the comparison was the effective area of the piston-cylinder assembly determined by gauge pressure measurements in the range from 0.7 MPa to 7.0 MPa. As the comparison reference value, the weighted mean of the results of the laboratories with primary pressure standards was used. With this reference value, all the participants who delivered the results demonstrated equivalence respective to the reference value within expanded uncertainties (k = 2) on all the range. The results of this comparison were linked to CCM key comparison CCM.P-K1.c. Also in relation to the reference values of CCM.P-K1.c, all participants demonstrated agreement within expanded uncertainties (k = 2) at all pressure points. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

This report describes a COOMET key comparison of hydraulic pressure standards of seven national metrology institutes that was carried out in the period from June 2005 to July 2008 in order to determine their degrees of equivalence in the range 10 MPa to 100 MPa of the gauge pressure. The pilot laboratory was VMT/VMC. The pressure standards of the participating NMIs were pressure balances of different design, equipped with piston–cylinder assemblies. The transfer standard was a pressure balance, equipped with a 9.8 mm2 piston–cylinder assembly, manufactured by SMU. The participants reported the pressure-dependent effective areas of the transfer standard at specified pressures. The reference values were calculated as the weighted means of PTB, NPL, SMU and VNIIM, which have primary pressure standards. The results by all participants agree with the reference values and with each other within the expanded uncertainties calculated with a coverage factor (k = 2). At the level of standard uncertainties there is a full agreement between 10 MPa and 100 MPa. The results of this comparison were linked to those of key comparison CCM.P-K7. Degrees of equivalence and expanded (k = 2) uncertainties between the COOMET and laboratories having participated in other KCs: CCM.P-K7, APMP.M.P-K7, EUROMET.M.P-K4 and APM.M.P-K7.1 at measured pressure points are presented in the final report. The results of the comparison demonstrate equivalence of the laboratory standards and, for laboratories the CMCs of which are not yet presented in the KCDB, this comparison provides a basis for submission in the range from 10 MPa to 100 MPa of hydraulic gauge pressure.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).