Working Principle Of Ultrasonic Flowmeter

- Jun 27, 2018 -

Ultrasonic flowmeters can be divided into the Doppler Effect method, the Transit time method(time difference method, the phase difference and frequency difference), the beam deflection method, correlation method, and the noise method. Currently, in the field of industrial measuring,ultrasonic flowmeters can be categorized into following two types: 2.1Doppler Effect method Doppler Effect methodmeasures the frequency shifts caused by liquid flow. In Doppler meters, two transducers are respectively installed in two cases attached to opposite sides of the pipe. A signal of known frequency is transmitted into the liquid to be measured. Solids, bubbles, or any other discontinuity in the liquid, cause the signal to be reflected to the receiving element. Since the liquid causing the reflection is moving, the frequency of the returned pulse is shifted. This frequency shift is proportional to the liquid's velocity or flow rate. The Doppler Effect methodbasing upon sound pulse reflection principle is shown inFigure 1. In Figure 1,the transmitting element launches anultrasonic wavewith frequency equaling to 1 .Solids, bubbles, or any other discontinuity in the liquid, cause the ultrasonic wave to be reflected to the receiving element changing the frequency to 2 .Then the difference between 1 and2 equals to Doppler frequency。