Design Of Ultrasonic Flowmeter Based On Difference Method

Ultrasonic flowmeter is the instrument which measures flow and rate by influence from liquid flow to ultrasonic. It is convenient for installation, for non-contact measurement and with wide range of measurement, so that it is widely applied in the petroleum, chemical, electricity, water delivery and other departments. It is in short application time in domestic and price is higher overseas, in hence, it needs to research and improve a lot.Through large quantity of literature and investigation, the paper conducts further study towards accuracy improvement and system's stability and reliability. With that, it designs a digital ultrasonic liquid flow measurement system based on time-difference method. Two probes are used for launching and receiving ultrasonic, accomplished by multiple pulse scheme. The measurement system can achieve higher precision.The major study accomplishments of this paper are as following:The design of the hardware structure of this system is as following: the ultrasonic transmitter circuit, the ultrasonic receiving circuit and the ultrasonic amplifying circuit as well as the filter circuit are designed. The data analysis indicates that the ultrasonic transmitter circuit herein can well stimulate the probe, which makes the ultrasonic probe give out the required 1Mhz ultrasonic suitable for the laboratory pipe. Through the pipeline, the sound waves will have a certain degree of attenuation and reflection and refraction caused by impurities, however, the acoustic amplifier circuit of the system can compensate for the signal attenuation through acoustic amplification while the filter circuit can filter out part of the noise in sound waves. The human-machine interface circuit required by the measurement system is programmed to achieve convenient operation as a human-oriented process. Under laboratory conditions, the suitable ultrasonic probe is selected by means of the measurement of the diameter of the pipe and propagation velocity of the ultrasonic wave in the water. The ultrasonic measurement system measures the velocity and flow of the fluid in the pipe in the laboratory, and then the error of the established system is tested by setting different flow rates. In this way, the error is analyzed and the problem is tackled.