Research On Liquid Micro-flow Metrology Method And Standard Device

In recent decades, many domestic and international researchers havestudied the instrument for measuring micro flow and obtained a wide range of results.But few standard device, aimed at micro flow, is worked for calibrating in themetrology institutes of our country. A standard device is proposed in this paper,based on the plunger working principle. It is used to calibrating micro-liquid-flow,ranging from1000mL/h down to0.1mL/h. It is able to realize the verification task ofcalibrating the glass tube flow meters, coriolis and thermal mass flow meters,infusion pump test. The following research work is completed in this paper:Firstly, the domestic and foreign research status of micro-liquid-flow issummarized in the paper, from two aspects of micro flow meter and micro flowstandard device. At the same time, domestic and foreign research achievements ofpiston flow standard device is consulted. The characteristics of micro flow aresummarized and the differences between it and regular flow are analyzed, from themethods of calibration. For calibrating the above four flow meters, correspondingmethods of verification are put forward in the paper from two aspects of verificationprocess and requirements. Then the overall design of the standard device is proposed.The primary standard of metrology is the plunger in this standard device. Thedynamic calibration method is used in the field of micro flow. Also the parallelstructure of four plungers is adopted in this device. The control system of the deviceis developed. Two sets of PLC are used as the core of the slave computer, in order toachieve plunger driving, valve control, signal acquisition, and other functions. Theupper computer is used, in order to achieve initialization settings, the entireverification process monitoring and other functions.Then the study of experiment and uncertainty are carried out in the paper.Through the comparison experiment, it confirmed that the standard device has goodconsistency with high precision balances and has a higher accuracy in wide flow raterange. The test repeatability is better than0.37%. The unit expanded uncertainty of stand volume flow rate of the device is0.52%(k=2). Finally the device is used toverifying the glass tube flow meters, coriolis and thermal mass flow meters, infusionpump test. The uncertainty evaluation was carried out for those experiments.