Research On High-Precision Ultrasonic Liquid Flowmeter Based On FPGA

Ultrasonic flowmeter has the advantages of non-contact, high-precision, wide measuring range, easy installation and maintenance etc. At present,the domestic existing ultrasonic flowmeter with time difference method has the defect of lower precision, so the research into high-precision ultrasonic liquid flowmeter with time difference method based on FPGA has enormous social and economic benefits. Precision measurement of ultrasonic transmission time is the key to solve the high-precision issues of ultrasonic flowmeter with time difference method.The measuring principle of ultrasonic flowmeter based on FPGA is presented and ultrasonic transducer is studied in this paper. Hardware circuit and software algorithm are designed for the precision measurement of ultrasonic transmission time. The following research results have been achieved:Ultrasonic transducer and the driving circuit of ultrasonic transducer are studied and designed, and the corresponding transmitting and receiving control circuit is developed,so as to obtain stable high-frequency ultrasonic signals.High-speed and high-resolution data acquisition system is researched, the data acquisition system based on high-resolution A/D and high-speed sampling system based on FPGA is constructed. The real-time data acquisition and the high-speed sampling data storage of high-frequency ultrasonic echo signals have been achieved.The collected sampling data is analyzed and processed with the software subdivision algorithm. The reasonable search algorithm of maximum characteristic waveform and the interpolation algorithm of accurate calculation the end point time of ultrasonic echo signal are developed. The ultrasonic transmission time is precision measured in nanosecond level by the software algorithm.Experimental verification device of ultrasonic flowmeter is designed; the experimental data of ultrasonic transmission time is obtained. Furthermore, experimental errors are analyzed and discussed during data processing. Experimental results show that the design of ultrasonic flowmeter based on FPGA is able to accomplish the precision measurement of ultrasonic transmission time in nanosecond level. The minimum resolution time of ultrasonic flowmeter is 0.122ns. The research on ultrasonic liquid flowmeter based on FPGA lays a solid foundation for the high-precision products development of ultrasonic flowmeter with time difference method.