Ultrasonic flowmeters have many kinds according to different measurement principles, which can be roughly divided into the following categories:
1. Propagation speed method (time difference method, phase difference method and frequency difference method);
2. Doppler method;
3. The correlation method;
4. Beam offset method, etc.;
But the most commonly used measurement methods are mainly two types: the time difference method and the Doppler effect method. At the same time, according to the use of different ultrasonic flowmeter, can be divided into fixed ultrasonic flowmeter and portable ultrasonic flowmeter.