The Design Of Embedded Low-power Ultrasonic Gas Flowmeter

In recent years, with the rapid development of the national economy and the construction of west to east natural gas project, the flow measurement is becoming increasingly important in practical applications. Ultrasonic gas flow meter is rapidly developed with an absolutely advantage in the field of flow measurement. Compared with the traditional meter, it has great application prospects without Baffles, non-contact detection, no pressure loss, wide turndown ratio, and measurement precision. It is a new flow measurement instruments. This topic is invested by Ningbo Peng Sheng Technology Co. Ltd. The domestic advanced level ultrasonic gas flow is developed through reading a lot of relevant literature, compared the advantages and disadvantages of ultrasonic flowmeter design schemes at home and abroad, and used the transit-time measurement principle.Ultrasonic gas flowmeter is overall firstly introduced, and then the working principle of transit-time ultrasonic gas flowmeter and the ultrasonic signal detection theory is analyzed. The appropriate frequency range is obtained by many experiments based studying the mechanism of ultrasonic signal propagation and attenuation concluded by the scholars at home and aboard. The ultrasonic transducer characteristic is analyzed. Japanese Murata produced transceiver integrated ultrasonic transducers is used. EFM32G890 is used as the microprocessor of entire system in this paper. The high-precision time-digital converter chip TDC-GP22 produced by ACAM company is used as the core timing measurements. The microprocessor as the core of hardware circuit is realized. System hardware circuit includes an ultrasonic transmitter circuit, a receiver amplifier, the switching circuit, a comparison circuit, and a liquid crystal display circuit. For the traditional zero-crossing detection signal counting, the requirements of circuit design are relatively high and the circuit is easily affected by the jamming signal. The first wave detection method is proposed to improve the accuracy of measurement of the time difference.Another important part of this issue is to write program to RAM. MCU modules are mainly included pressure module, temperature module, the first wave detection module, TDC-GP22 timing module, communication module 485, LCD module and so on. Modular programming is used in the program. It is easy to debug, and can be well completed the core control function of EFM32G890. After the commissioning of the entire system, it is tested in the gas test chamber of Ningbo Peng Sheng Technology Co. Ltd. The experimental results show that the design of mono gas ultrasonic flowmeter of this project has working stable, high accuracy, good repeatability, high performance, and anti-jamming strong. And it can reach the leading level at home and aboard.