Research On The Active Plunger Liquid Small Flow Standard Device

Flowmeters are closely related to industrial and agricultural production,scientific research,national defense,and people's lives,and contribute greatly to economic construction,scientific and technological development,and environmental protection.With the increase in the number of flow meters and the improvement of related test technologies,the requirements for calibration devices are becoming more and more rigorous.Especially in the field of liquid small flow metering,since more standard devices based on mass method and volume method are used today,more limitations are highlighted,and new breakthroughs are urgently needed.Based on the in-depth study of the piston liquid flow standard device and its key technologies,and in combination with customer needs,a set of active ram type liquid small flow standard device with pure water as the verification medium was developed.The main work of this paper is as follows:(1)Combining with relevant literatures at home and abroad,the research status and significance of piston flow standard devices are analyzed and summarized.(2)According to the working principle of the active piston flow standard device,combined with its technical indicators,the design of the overall scheme of the device and the establishment of the flow mathematical model are completed.(3)According to the control mode,flow range and workload of the device,the design of the power system of the device is completed,and the servo motor,servo drive and ball screw are selected and calculated.The mechanical structure of the device was designed with SolidWorks and the drawings were processed.(4)Combined with PLC and LabVIEW,the standard device's measurement and control system was designed to automate the action control,data acquisition and processing.The millisecond timer was created by the PLC interrupt function,and the pulse signal and time synchronization acquisition was realized by pulse interpolation technology.(5)Performance testing and uncertainty assessment of the prototype of the device was completed.The experimental results show that the device flow range is within(20~2000)L/h,and the stability is good,the volume repeatability is better than 0.02%,and the expansion uncertainty is 0.062%(k=2).After verification by the relevant technical department at the higher level,the standard device meets the requirements for establishing the standard,which improves the verification efficiency of the small flow meter.