Research and Implementation of Automatic Gain Control Method for Time-Difference Ultrasonic Gas Meter

The time difference method is the most widely used method in the field of ultrasonic flow measurement. In order to solve the cycle-skip problem caused by the first wave identification error which is easily occurred in the time difference method, an automatic gain control (AGC) method is proposed in this paper. Firstly, the working principle of ultrasonic gas meter with time difference method and the cycle-skip problem with threshold method are analyzed. And then the system architecture based on AS6040 time-to-digital converter chip is designed, focusing on the research of AGC method and realizing the method based on AD8338 chip. The AGC method can keep the amplitude and envelope of the ultrasonic echo signal relatively stable under extreme temperature and flow rate conditions. The results of high and low temperature and flow calibration experiments show that the time-differential ultrasonic gas meter based on the AGC method can achieve class 1.5 accuracy in the flow range from 0.16 m
³
/h to 30 m
³
/h.