Design and Implementation of the A/D Conversion Circuit for the High-Accuracy Ultrasonic Flowmeter

Ultrasonic flow meter has been widely applied in the area of meteorology, petroleum, chemical engineering, medicine, water resources management and so on, owing to its advantages of high-accuracy, non-blocking measurement, easy installation and low cost. The A/D conversion circuit design is the core of the data acquisition system for high-accuracy ultrasonic flow meter. According to the data acquisition issues of high-accuracy ultrasonic flow meter in time-difference method, a two-channel 12-bit low-power monolithic CMOS analog-digital conversion ADC12DL040 chip and ARM microprocessor LPC2138 was adopted to design the data acquisition system. The time-difference ultrasonic flow meter theory was described in this paper, the A/D chip and ARM design circuit were given, the hardware structure and software flowchart have been presented. The experimental results showed that the designed A/D conversion circuit be able to reach the resolution of 1~2 ns,the minimum resolution time is 0.305ns, the resolution in nanosecond level for the time-difference of ultrasonic wave propagating between downstream time and upstream time have been reached. The production cost was reduced owing to the designed A/D conversion circuit. Generally the design and implementation of A/D conversion circuit lay the solid foundation for the high-accuracy ultrasonic flow meter.