Micro-flow calibration system based on a new diverter valve design

Micro-flow meters are expanding their flow range and improving measurement accuracy, which brings new challenges to their calibration. For micro-flow calibration, one of the challenges is to maintain a stable and accurate flow through the calibration runs. Other challenges also include evaporation, degassing, surface tension, and temperature variation. This paper combines the theories with experiments to analyze the source of each uncertainty component and deal with them in the control system. Most importantly, a new diverter valve has been developed to specifically address the challenge. This novel design can accomplish both the standing-start-and-finish method and the flying-start-and-finish method. As a result, the system can calibrate flow in the range of 0.1-80g/min, and the expanded uncertainty of the calibration rig was estimated to be 0.12% at 95% confidence level.