Research on calibration method and uncertainty evaluation of thermal gas mass flowmeter

The thermal mass flowmeter has simple structure and wide measurement range. It can be divided into capillary thermal mass flowmeter and plug-in thermal mass flowmeter. In order to accurately measure the thermal gas mass flowmeter, the passive gas piston provers (standard device) was selected to measure it. and the measurement uncertainty of the standard device was analyzed. Three test points are selected to test at three pistons, and the repeatability of the measurement results and the expanded uncertainty of the measurement results are analyzed at the same time. The expanded uncertainty <i>U</i>_rel is 0.19% (<i>k</i>=2), which is proved that the calibration of the thermal gas mass flowmeter with passive gas piston provers (standard device) is effective. The uncertainty of the measurement results is small and the reliability is high.