An ultrasonic flowmeter measures the velocity of a fluid with ultrasound to calculate volumetric flow.
The sound waves are usually at a frequency beyond the range of hearing. The ultrasound signal is sent into a stream of flowing liquid by using wetted (insertion) transducers that make direct contact with the liquid or external (clamp-on) transducers, which send the ultrasound through the pipe wall.
A clamp-on ultrasonic flow meter consists of at least two ultrasonic sensors mounted externally to a pipe. Flow rate depends on the nature of the application.
How Does an Ultrasonic Flowmeter Work?
The flowmeter operates by alternately transmitting and receiving a burst of ultrasound between the two transducers, measuring the transit time that it takes for sound to travel between the two transducers in both directions.
The transmitter processes signals from the transmitted wave and its reflections to determine the flow rate.
At no flow conditions, the frequencies of an ultrasonic wave transmitted into a pipe and its reflections from the fluid are the same. Under flowing conditions, the frequency of the reflected wave is different.
The latest iteration of transit-time ultrasonic flowmeters make it possible to track fluid movements down to a true zero flow condition.
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What are Ultrasonic Flowmeters Used For?
Ultrasonic flowmeters are ideal for applications involving water-based or sonically conductive dirty process fluids. They can also measure flows of non-conductive fluids.
These flowmeters can be applied to measure the velocity of liquids that allow ultrasonic waves to pass, including water, molten sulfur, cryogenic liquids, and chemicals.
The industries that use these meters include oil and gas, water and wastewater, power, chemical, food and beverage and more.
Ultrasonic transit-time clamp-on meters are most often used in industrial flow measurement as they are cost-friendly, smaller, and more accurate. These clamp-on transducers are often used when piping cannot be disturbed. By avoiding contact with the process, the meters cannot become fouled or damaged by caustic fluids, eliminating the need to manage any waste products left in the line.