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Gas Flow Standards and Their Uncertainty



John D. Wright, Aaron Johnson, Michael R. Moldover, Shin-ichi Nakao


We review diverse types of gas flow standards that are used to calibrate other gas flow meters. For each type of standard, we describe the principles of its operation and at least one hardware example. We identify the practical limits of the example's performance, and, in many instances, we provide an uncertainty budget for a typical flow. The reviewed standards span the flow range 2.2 × 10-7 g/s to 520 kg/s. The references point to standards that operate at higher and at lower flows. The reviewed standards include volumetric flow standards (piston and bell provers, pressure-volume-temperature-time standards, rate-of-rise standards), static and dynamic gravimetric flow standards, and velocity × area standards such as critical flow venturis, laser doppler anemometer surveys, and multipath-ultrasonic meters.


gas flow, primary standard, working standard, gravimetric, piston prover


Wright, J. , Johnson, A. , Moldover, M. and Nakao, S. (2022), Gas Flow Standards and Their Uncertainty, Metrologia, [online],, (Accessed July 22, 2024)


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Created December 12, 2022, Updated June 23, 2023