A Small Flow Point Signal Processing and Measurement Method for Ultrasonic Gas Meter

Due to the advantages of no loss of pressure and wide range, ultrasonic gas meter is becoming a hot research and application at home and abroad. For low power ultrasonic gas meter, a key problem is to improve the precision and stability of the small flow point measurement with the impact of circuit and environment and the influence of turbulence and pulsating flow. In this paper, the ultrasonic propagation time values and their difference values are achieved by using the method of threshold value and the one-half VCC “zero” point detection. The feature point of the arrival time is defined by the threshold value of the echo, which is the zero-crossing point of the next echo period. Propagation time and the differences can be obtained from several feature points that satisfy the threshold of echo. The measurement value at each time is obtained through the average filter process of these difference values. By using the improved Kalman filtering algorithm in flow measurement data processing and adjusting the values of Q and R, the measuring accuracy and stability are improved, respectively, in the small flow point affected by the disturbance and pulsating flow. The latest application circuit introduced by TI company has been used in the ultrasonic gas meter circuit and system design, and the calibration experiment of ultrasonic gas meter has been completed. The experimental results show that the measurement accuracy and repeatability can meet the requirements of the application.