Study On An Ultrasonic Gas Flowmeter With Double-Channel Based On Time Difference Measurement

The gas ultrasonic flowmeter has the advantages of small pressure loss,wide range ratio,no moving parts,high degree of electronic and digital integration.So it has been widely used in high-pressure and large-diameter gas flow measurement.However,the accuracy and stability of flow measurement are limited due to the problems of small pipe diameter,few ultrasonic sensors,large attenuation of ultrasonic signals,small signal-to-noise ratio and severe acoustic noise interference in the measurement of low-pressure small-diameter gas flow.In order to solve the above technical problems,this paper focus on the research of double-channel gas ultrasonic flowmeter in low pressure application,and its prototype of DN50 is designed.Firstly,the first threshold voltage of time difference measurment is set by the adaptive threshold method and proportional threshold method to ensure the accuracy of the transit time measurement.Then,the echo signal switching circuit is adopted to the same signal processing circuit and it will reduce the difference in circuit's delay.At the same time,the peak detection module and the step acquisition module are designed to measure the the maximum amplitude measurement and amplitude of each peak of the echo signal.Finally,the corresponding program is designed to adjust the first threshold and the echo signal magnification to ensure accurate measurement of the time difference of each channel.The double-channel time difference fusion method is designed in this paper and the gas volume flow in the pipeline is obtained.The experiment of the prototype of the double-channel gas ultrasonic flowmeter is carried out including temperature experiment and flow experiment.The results show that the prototype designed in this paper meets the design requirements and has high measurement accuracy and reliability.