Research On Key Technologies Of Coriolis Mass Flowmeter In Experiments And Applications

Coriolis mass flowmeter which can directly measure the mass of flow is one ofthe fastest growing flowmeters currently, owing to its high precision, goodrepeatability and measurements of multi-parameters in different fluid conditions. Inthis thesis, several key problems in experiments and applications of Coriolis massflowmeter are researched and analyzed, and some effective solutions are proposed.For the crash problem of flow transmitters working in the high temperatureenviroment, many temperature tests are conducted for the digital Coriolis massflowmeter based on DSP, the reasons why DSPs crash are analyzed, and somecountermeasures of high temperature resistant are also proposed. The experimentalresults show that these countermeasures are feasible and effective.For the mismatch problem between the primary meter and transmitter ofCoriolis mass flowmeter, a steady-state amplitude diagram analysis method for theanalog drive circuit is proposed to analyze the matching processes such as startup,steady-state oscillation and working in high temperature environment. Somebest-match measures are present to shorten the start-up time3seconds, raise thedrive efficiency by20%and ensure normal operation of the flowmeter in the hightemperature environment of60℃. The experimental results show that thematching method is simple, feasible and effective.For the high frequency problem of Coriolis microbending sensor, a newhigh-frequency signal processing hardware platform is developed which is based onthe high performance DSP TMS320C6726. Optimizing power circuit designreduces the system power consumption. The expansion of external peripheralcircuits increases the resources of system. High precise signal conditioning andacquisition circuits improve system measurement accuracy, while output andcommunications circuits improve the system function. Electrical signal test resultsshow that the measurement accuracy of the transmitter reaches0.1%for both301Hz and701Hz signals with noise. And the field experimental calibration resultsshow that for the V70type primary instrument of TaiHang, the measurementaccuracy of the transmitter is greater than0.1%with the turn-down ratio of13:1,and the repeatability reaches0.05%.For the experimental and calibration problems of Coriolis mass flowmeter, a muti-functions experimental apparatus is studied and designed. The measuringmethods and calculation process of the uncertainty and flow stability of theapparatus are analyzed, while various factors that affect the calibration accuracy offlowmeter are summarized.