measure fluid velocity by passing high-frequency sound waves along the fluid
flow path. Fluid motion influences the propagation of these sound waves, which may then be
measured to infer fluid velocity. Two major sub-types of ultrasonic flowmeters exist: Doppler and
transit-time. Both types of ultrasonic flowmeter work by transmitting a high-frequency sound wave
into the fluid stream (the incident pulse) and analyzing the received pulse.