Multichannel Ultrasonic Gas Flow Meter Signal Processing Module Design

Ultrasonic Flowmeter is a non-contact instrument with the rapid development of IC technology. In the measurement of gas fields, the most widely used measurement method is the time difference method. Time difference method is by measuring the ultrasonic signal in the gas in the downstream and upstream propagation time difference to reflect the flow of fluid. Ultrasonic Flowmeter is non-contact measurement, accurate and reliable measurement, no pressure loss, high precision, energy saving, etc., so ultrasonic flowmeter is an ideal energy-saving flow meter, with a very broad application prospects.This project was invested by Quanzhou RiXin Flow Instrumentation Company. After a lot of research and analysis and comparative analysis of various kinds of ultrasonic flowmeters, advanced multi-channel ultrasonic gas flowmeter was developed.First of all ultrasonic flowmeter is introduced a whole, and then analyzes the working principle of ultrasonic flowmeter and ultrasonic signal detection theory, and at the same time the characteristics of ultrasonic sensors are introduced. In this project the center frequency of ultrasonic sensor selected is 200KHz. Then introduced the whole design of the project, and MCU + FPGA program is selected for the whole design. In this design MCU is to control the entire system and do data acquisition and analysis, and FPGA is mainly for high precision timing. The subject selected MCU is LPC936 which integrates a lot of modules, and this can not only simplify the circuit design, but also improve the stability of the system. The selection of FPGA is EP2C5Q208C8 of ALTERA's CycloneII series, and FPGA high speed timing circuit module ensures high-precision measurement of the system. The subject of the important hardware design circuit is automatic gain control circuit design, the circuit ensures the stability of received ultrasonic signal, and this is very important for further signal processing.Another important part of this project is MCU programming. MCU program modules mainly included ultrasonic transmitter and receiver module, AGC module, data transfer with FPGA module, data analysis module and so on. Program used modular programming which can facilitate the upgrading and debugging for future, and at the same time complete the MCU's core control function.After system completed, test was finished in Quanzhou RiXin Flow Instrumentation Company gas test room, and laboratory results show that the multi-channels ultrasonic gas flowmeter works stably and reliably, and has high measurement precision. The multi-channels ultrasonic gas flowmeter's performance reached design of the pre-set goals.