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Volumetric Gas Flow Standard with Uncertainty of 0.02% to 0.05%



John D. Wright, Michael R. Moldover, Aaron N. Johnson, A Mizuno


A new pressure, volume, temperature, and time (PVTt) primary gas flow standard for calibrating flowmeters has an expanded uncertainty (k = 2) of between 0.02% and 0.05%. The standard diverts a steady flow into a collection tank of known volume during a measured time interval. The standard spans the flow range of 1 slm^1 to 2000 slm using two collection tanks (677 L and 34 L) and two flow diversion systems. We describe the novel features of the standard and analyze its uncertainty. The thermostatted collection tank allows determination of the average gas temperature to 7 mK (0.0023%) within an equilibration time of 20 minutes. We developed a mass cancellation procedure that reduced the uncertainty contribution from the inventory volume to 0.021% at the highest flow rate. Flows were independently measured throughout the overlapping flow range and they agreed within 0.015%. The larger collection system was evaluated at high flows by comparing single and double diversions; the maximum difference was 0.0075%.
Journal of Fluids Engineering-Transactions of the Asme
No. 6


correlated uncertainty, gas flow standard, inventory volume, mass cancellation, PVTt standard, sensor response, uncertainty


Wright, J. , Moldover, M. , Johnson, A. and Mizuno, A. (2003), Volumetric Gas Flow Standard with Uncertainty of 0.02% to 0.05%, Journal of Fluids Engineering-Transactions of the Asme, [online], (Accessed June 23, 2024)


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Created November 1, 2003, Updated February 17, 2017