Development of a calibration facility for small mass flow rates of gas and the uncertainty of a sonic venturi transfer standard

Abstract

A calibration facility based on the gravimetric method has been developed at NRLM for small mass flow rates of gas. This calibration facility establishes a primary gas flow measurement standard with a combined standard uncertainty of ±0.105% at maximum, for mass flow rates up to about 5 g/min. Two differently sized sonic venturis were tested using this facility and the results show that they can work well as a flow transfer standard for small mass flow rates. It is also shown that these sonic venturis can be used to establish flow transfer standards with a combined standard uncertainty of ±0.112% for the larger venturi and ±0.089% for the smaller venturi.