Establishment of micro liquid flow facility at NIM

Abstract

National Institute of Metrology (NIM) has established a micro liquid flow facility based on dynamic weighing method, with the flow rate range of 100nL/min–150 mL/min. The facility includes two sets of high accuracy electronic balances and three Coriolis mass flowmeters as the main standard. An acquisition method of weighing value based on the fluctuation frequency is adopted to effectively reduce the uncertainty introduced by dynamic reading. A ‘dual time’ method is used to realize the synchronization between weighing system and meter under test by the 'time stamp' with resolution of 1 ms. The uncertainty sources of balance that come from weighing accuracy of mg magnitude, short-term drift and long-term stability are evaluated by experimental method. The results show that the facility uncertainty is better than 1.5 %(k = 2) at 100nL/min flow rate, and the uncertainty is better than 0.1 %(k = 2) when the flow rate is above 1 mL/min. The micro liquid flow facility developed in this paper provides an important calibration experimental platform for the development and performance improvement of micro flow sensors.