EXPERIENCE WITH GRAVIMETRIC FLOW STANDARD (GFS) IN VACUUM AND HERMETIC MODE

Zdeněk Krajíček, Martin Vičar, Dominik Pražák, Jiří Tesař, Tomáš Hajduk, Ladislav Peksa, Tomáš Gronych, Martin Jeřáb
Abstract:
The Czech national standard of low gas flow is based on a gravimetric flow standard (GFS) principle. It means it defines the flow as the mass loss of gas from a pressure bottle which is continuously weighed. This weighing is performed in an ambient atmosphere which causes that the main source of uncertainty results from the buoyancy correction. This buoyancy correction is complicated by the instabilities of the atmospheric environment and by the fact that volume of the weighed pressure bottle is dependent both on temperature and internal pressure. By modifying the experimental set-up of the GFS utilizing weighing in vacuum, it is possible to suppress the problematic buoyancy effects and moreover to eliminate other impractical side effects such as water vapour condensation on the pressure bottle due to cooling below dew point for the higher flow rates. This presentation describes the practical problems of the vacuum modification of the GFS together with the uncertainty analysis of the modified experimental set-up and the measurement results. The hermetic mode and its main applicability is also introduced.
Keywords:
equivalence of national standards, flow metrology, gravimetric flow standard
Download:
IMEKO-WC-2015-TC9-220.pdf
DOI:
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Event details
Event name:
XXI IMEKO World Congress
Title:

Measurement in Research and Industry

Place:
Prague, CZECH REPUBLIC
Time:
30 August 2015 - 04 September 2015
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