Gas Flowmeter Calibrations With the Working Gas Flow Standard
John D. Wright, Jean-Phillipe Kayl, Aaron N. Johnson, Gina M. Kline
The Working Gas Flow Standard (WGFS) uses critical venturis, critical nozzles, or laminar flowmeters as working standards to calibrate customer flowmeters. The working standards are periodically calibrated with primary standards: the 34 L, 677 L, or 26 m3 PVTt standards, or a static gravimetric standard. The WGFS is used to calibrate flowmeters with low pressure drop, in dry air, at flows from 0.001 L/min to 70000 L/min with uncertainty of 0.15 % or less. At flows less than 2000 L/min, calibrations in other non-hazardous and non-corrosive gases are available.In this document, we provide an overview of the gas flow calibration service and the procedures for customers to submit their flowmeters to NIST for calibration. We also document the flow calculation algorithms and uncertainties of the WGFS.