Within the Euromet region a regional key comparison (Euromet.M.P-K1.b) was carried out in order to compare national vacuum standards in the pressure range from 3 × 10-4 Pa to 0.9 Pa. The participants were the BNM-LNE (France), CEM (Spain), IMGC-CNR (Italy), IMT (Slovenia), NPL (United Kingdom), UME (Turkey), and the PTB (Germany) as pilot laboratory. The measurements were carried out from April 2000 to February 2002.Two spinning rotor gauges served as transfer standards and showed a good transport stability. The effective accommodation coefficients of the rotors had to be determined at eight target points at and between 3 × 10-4 Pa and 0.9 Pa. The uncertainty of the generated pressure in the calibration standard was reported as part of the calibration report by each laboratory. All additional uncertainties that were related to the transfer standard were evaluated by the pilot laboratory in order to have a uniform uncertainty analysis for all participants and in order to emphasize the importance of the reported uncertainty of the generated pressure.From the available data a Euromet reference value was calculated at each target pressure. The results from most of the laboratories showed a good agreement with the reference value within the combined uncertainties. A few values of three of the laboratories were significantly off the reference value.At the highest target pressure of 0.9 Pa a linkage to the lowest target pressure at 1 Pa of the key comparison CCM.P-K4 was possible by means of the results of three laboratories that took part in both comparisons.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 Mutual Recognition Arrangement (MRA).
A new primary standard for generation of vacuum pressures between 9 × 10 −4 Pa and 10 3 Pa has been completed at the Ulusal Metroloji Enstitüsü (UME). It is based on the static expansion method, whereby the range is extended to lower pressures by multiple expansions. The apparatus consists of six vessels that provide a pressure reduction by a factor of about 10 −6 in the main calibration vessel after a three-step expansion. Seventeen platinum resistance thermometers are mounted on the vessels to determine the correction due to temperature effects. The whole apparatus is built using the UHV technique and can be baked up to 400 ˚C. The expanded (k = 2) relative uncertainties of pressures, generated by this new standard, range from 2.1 × 10 −3 at 9 × 10 −4 Pa to 9.5 × 10 −4 at 10 3 Pa.
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