Gas flow standards and their uncertainty

Abstract

We review primary and working gas flow standards that are used to calibrate gas flow meters. For each type of primary standard, we describe the principles and practical considerations of its operation and describe one example implementation. 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−1 to 520 kg s−1. 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. Finally, we describe working standard flow meters used in parallel to attain higher flows than economically practical via primary methods.