Design Of Ultrasonic Flowmeter Based On FFGA

Ultrasonic flow measurement technology which can measure the flow of fluid, which according to fluid flow modulates propagation velocity of ultrasonic wave. In recent years, with the development of signal processor technology, application of large-scale digital circuits, and the emergence of new ultrasonic transducers, the ultrasonic flow measurement technology has obtained a great advancement, which has the advantages of high-precision, non-contact, easy installation and maintenance, wide range of applications, intelligent, convenient temporary monitoring etc. It is widely used in industrial production, oil and gas exploration, aerospace, nuclear energy usage, medical testing and many other fields.Through reading large number of literatures, on basis of absorbing and referring to the domestic and foreign advanced technology, the paper introduces basic principle and realizing method of the ultrasonic flow measurement technology, research projects of ultrasonic flowmeter based on FPGA chip is determined. Factors affecting the measurement accuracy of ultrasonic flowmeter is detailed analyzed, on this basis, given the system design ideas. The following research results have been achieved:The first step is to send and receive high-quality ultrasonic wave. Stable ultrasonic transmitting signal is gained based on detailed research and development of ultrasonic transmitter circuit, including transducer selection, drive circuit, transducers switching control circuit. Received signal is processed by three filtering and amplification. By high-speed comparator circuit and FPGA processing obtained suitable measurement module of the stop signal.The flow rate algorithm of ultrasonic flowmeter is improved in this paper, and in a certain extent, reducing the impact of temperature on the measurement accuracy. Furthermore, added time and flow rate correction in algorithm, to further improve measurement accuracy. Transmission time is a key factor to affect the accuracy of ultrasonic flowmeter. The ultrasonic transmission time is multiple precision measured by time measurement chip TDC-GP2of German ACAM Company and made average consideration. Combination of FPGA amends it, established the delay window to eliminate noise interference, and improved the measurement accuracy of the downstream and upstream time. The movement of viscous fluid is complex in a circular pipe, so it must be corrected line average velocity in measurement to require high precision. Otherwise, the measurement accuracy is difficult to guarantee. This paper analyzes and derives the flow rate correction coefficient in different state of motion. Combination of FPGA, according to calculate to judge the state of fluid of motion. Further to amend the flow rate according the state of motion, improve the measurement accuracy.Experimental device of ultrasonic flowmeter is designed in this paper, by measured the experimental waveforms of each module to verify the correctness of the design. Time resolution has achieved up to0.1ns by debugging time measurement module. This paper lays a solid foundation for researching and developing high-precision ultrasonic flowmeter.