Development of the Calibration Facility for Small Mass Flow Rates of Gases and the Sonic Venturi Nozzle Transfer Standard

A calibration facility based on the gravimetric method has been developed at NRLM for small mass flow rates of gases. This calibration facility establishes a primary gas flow measurement standard in Japan with an expanded maximum uncertainty of ±0.12 percent for small mass flow rates from 0.1 g / min to 50 g / min for nitrogen gas. Five sonic Venturi nozzles were tested using this facility and the results showed that they can work well as a flow transfer standard for small mass flow rates. These sonic Venturi nozzles can be used to establish flow transfer standards within an expanded uncertainty of ±0.15 percent.