Ultrasonic heat meters

Ultrasonic meters use ultrasonic waves to measure the flow rate of a fluid in a pipe. Devices that use the Doppler principle emit ultrasonic waves into a fluid at a constant frequency and receive waves reflected from solid particles or from bubbles dispersed in the fluid. Due to the movement of particles or bubbles with the fluid, the frequency of the received ultrasonic wave is different from the frequency of the transmitted wave. The difference in frequencies is then proportional to the fluid flow rate.

Advantages: no moving parts, lower pressure losses, the liquid can be aggressive and explosive

Disadvantages: possible errors depending on temperature, density, viscosity and particle concentration