A key comparison of low absolute pressure standards, organized under the auspices of the Consultative Committee for Mass and Related Quantities (CCM), was carried out at seven national metrology institutes (NMIs) between March 1998 and September 1999 in order to determine the degrees of equivalence of the standards at pressures in the range 1 Pa to 1000 Pa. The primary standards, which represent two principal measurement methods, included five liquid-column manometers and four static expansion systems. The transfer standard package consisted of four high-precision pressure transducers: two capacitance diaphragm gauges to provide high resolution at low pressures, and two resonant silicon gauges to provide the required calibration stability. Two nominally identical transfer packages were used to reduce the time required for the measurements, with Package A being circulated among laboratories in the European region (Istituto di

This report describes a CCM key comparison of absolute pressure at five National Metrology Institutes (NMIs) that was carried out from August 1998 to May 2002. The goal of the key comparison was to determine the degree of equivalence of NMI standards at pressures in the range of 3×10 -6 Pa to 9×10 -4 Pa. The primary standards were dynamic expansion standards at four of the NMIs and a series expansion standard at the fifth NMI. The transfer standard package consisted of two spinning rotor gauges (SRGs) and three Bayard-Alpert ionization gauges. Due to equipment malfunctions, only one of the ionization gauges was calibrated by all of the participants. The SRG measurements were used to compare NMIs at 9×10 -4 Pa and to normalize the ionization gauge results at that same pressure. The ionization gauge measurements were used to compare NMIs at the lower pressures. The degrees of equivalence of the NMI standards were determined in two ways: deviations from the key comparison reference value (KCRV), and pairwise differences between those deviations. The standards of four of the NMIs show equivalence to the KCRV and each other over the full range of pressures relative to the expanded uncertainties of the comparisons at the k=2 level. The standard of one NMI was equivalent to the KCRV at 3×10 -6 Pa only, and showed lack of equivalence to the standards of one or more NMIs in the range of 9×10 -6 Pa to 9×10

The paper describes the results of a comparison of two primary low-pressure standards, (i) the Ultrasonic Interferometer Manometer (UIM) and (ii) the Static Expansion Apparatus (SEA), maintained at the National Physical Laboratory (NPLI), India. The comparison was carried out by employing a capacitance diaphragm gauge (CDG) of 1333 Pa full-scale range as the transfer standard over the pressure range 1 Pa to 1000 Pa. For pressures of 20 Pa and above, the values of the calibration factor of the CDG obtained on the SEA deviate 0,10 % from the values by the thermal transpiration equation and this deviation increases to over 0,4 % for pressures lower than 20 Pa. For the UIM, the deviation is found below 0,05 % at pressures of 100 Pa and above, but increases to 0,8 % for pressures as low as 1 Pa. The comparison (i) establishes the mutual compatibility of the two primary standards in the region of pressure overlap and (ii) sets limits to the uncertainty of measurements made on the two systems, which are 0,2 % at 1000 Pa and 1,0 % at 10-4 Pa for the SEA and 0,0014 % at 1000 Pa and 1,4 % at 1 Pa for the UIM.

Quantitative leak tests with vacuum technology have become an important tool in industry for safety and operational reasons and to meet environmental regulations. In the absence of a relevant key comparison, so far, there are no calibration measurement capabilities published in the BIPM data base. To enable national metrology institutes providing service for leak rate calibrations to apply for these entries in the data base and to ensure international equivalence in this field, key comparison CCM.P-K12 was organized. The goal of this comparison was to compare the national calibration standards and procedures for helium leak rates. Two helium permeation leak elements of 4×10−11 mol/s (L1) and 8×10−14 mol/s (L2) served as transfer standards and were measured by 11 national metrology institutes for L1 and 6 national metrology institutes for L2. Equivalence could be shown for 8 laboratories in the case of L1 and for all 6 in the case of L2. Three different evaluation methods were applied and are presented in this report, but the random effects model was accepted as most suitable in our case.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).

The paper describes the results of a comparison of low-pressure standards maintained at the National Physical Laboratory (NPL, India) and the Physikalisch Technische Bundesanstalt (PTB, FRG) over the range 10−3–2 Pa. The intercomparison was carried out by employing spinning rotor gauges shipped with a novel transport device. Both the laboratories, i.e., NPL and PTB, use static expansion systems for pressure generation. The gauge coefficients σ0,eff of the two gauges for Ar agree within ±0.5% for the two laboratories. This result proves agreement of the respective national standards in the above range of pressures. The small deviation of −0.4% between calibrations over a period of one year before and after air-parcel transportation from Berlin to New Delhi and back is indicative of a careful handling of the rotors during operation and a good performance of the employed transport device.