There are two types of ultrasonic flow meter technologies, including Doppler and transit time. In addition to inline and open channel models, ultrasonic meters are available as clamp-on solutions when contact with the measured fluid is not possible.
The ultrasonic flow meter operates by alternately transmitting and receiving a burst of ultrasound between the two transducers by measuring the transit time that it takes for sound to travel between the two transducers in both directions