A constant pressure gas flowmeter using a directly driven diaphragm bellows as a volume displacer was studied. This flowmeter is perfectly vacuum-sealed, does not contain elastomers and liquids that would prevent outgassing at elevated temperatures and can achieve a smaller ratio of the final volume to the displaced volume than when bellows are used, so that the uncertainty in generating small flow rates can be small. As, when a bellows is used in the volume displacer, the displaced volume cannot be calculated from the geometric dimensions and its dependence on the displacement is non-linear, a sensitive method had to be developed for measuring this dependence. The uncertainty in measuring the displaced volume by this method and the achieved uncertainty of the flowmeter were determined.
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).
This report describes a EURAMET comparison of five European National Metrology Institutes in low gauge and absolute pressure in gas (nitrogen), denoted as EURAMET.M.P-K4.2010. Its main intention is to state equivalence of the pressure standards, in particular those based on the technology of force-balanced piston gauges such as e.g. FRS by Furness Controls, UK and FPG8601 by DHI-Fluke, USA. It covers the range from 1 Pa to 15 kPa, both gauge and absolute. The comparison in absolute mode serves as a EURAMET Key Comparison which can be linked to CCM.P-K4 and CCM.P-K2 via PTB. The comparison in gauge mode is a supplementary comparison.
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