Full Description This standard describes transit-time ultrasonic flowmeters for water supply service application in pipes running full. An ultrasonic flowmeter is a meter that uses acoustic energy signals to measure liquid velocity. There are currently two distinct types of ultrasonic flowmeters available: Doppler-effect and transit-time. The Doppler-effect meter is used exclusively for liquids containing solid particles or gases, and the transit-time flowmeter is used in a wide variety of applications in the water industry.