Design Of Time-difference Method Gas Ultrasonic Flowmeter Based On DSP

Gas ultrasonic flowmeter is becoming more and more important because of itsnon-contact measurement, no loss of pressure, wide turndown ratio, etc in the field ofindustry and trade measures. Many countries have taken gas ultrasonic flowmeter as gasdetection system of natural gas trade settlement. However, due to characteristics ofultrasonic in gas transmission, the process of gas ultrasonic flowmeter development isbeing restricted by now. Currently, there is a big gap between the technology of gasultrasonic flowmeter of domestic and foreign. The key technology of it is held by only afew manufacturers abroad.Two key technologies including signal processing and zero-crossing detection to theeffect of gas ultrasonic flowmeter’s accuracy is studied in this paper. Wavelet de-noisingis introduced to the signal processing, the method of threshold is improved, and it hasbeen verified in the simulation experiments. Two methods of determining the base peakbased on the concept of energy are put forward, and the performances of the two methodshave been compared. The measurement algorithm has been simulated by MATLAB, andthe simulation results are all presented.TMS320F28335is used as the main control chip in the gas ultrasonic flowmeterdiscussed in this paper. The circuits of DSP peripheral, ultrasonic transmitter andreceiverare are designed according to the specific needs of the gas ultrasonic flowmeter.A complete hardware design block diagram and specific design of software are given inthe paper, and all the parts of software flow chart are drawn.TMS320F28335has abundant peripheral resources as well as the working frequencyup to150MHz, which makes the DSP chip can finish almost all the work of the fowmeterand simplify the hardware design of the system. The accuracy of measurement isimproved, precision can reach to1.0magnitude. The system has a highly real-time at thesame time.