What is an Ultrasonic Flow Meter?

An ultrasonic flow meter measures the flow of a liquid or gas by sending ultrasonic waves across a pipe, which contain the flow in the direction of flow and in the opposite direction of flow. The ultrasonic waves and the flow rate of the liquid or gas can be combined to determine the flow rate.

The sound waves usually have a frequency beyond the range of hearing. The ultrasonic signal is sent into a flowing fluid using wetted (insertion) transducers that make direct contact with the fluid or external (clamp-on) transducers, which send the ultrasonic sound through the pipe wall.

A clamp-on ultrasonic flowmeter consists of at least two ultrasonic sensors mounted externally on a pipe. The flow rate depends on the nature of the application.

How does an Ultrasonic Flowmeter work?

The first ultrasonic flowmeter was introduced in 1959 by a Japanese inventor. This one used doppler technology to measure blood flow. In the early 1960s, flow meters were used as industrial instruments for measuring the flow of gases and liquids. Since their early days, they have become the main product for many instrument manufacturers.

A flowmeter measures the volume of flow of liquids and gases to provide accurate readings for flow control. Many industrial applications, such as chemical companies, require precise readings for production processes.

An ultrasonic flowmeter uses acoustic sounds to measure flow. There are two types of ultrasonic flow measurement methods, transit time travel and Doppler shift. The difference between the methods is how the directional measurement is obtained. In the time travel method, sound waves are sent along a diagonal to the flow and measurements are taken in both directions. In the Doppler method, sound waves are projected along the flow path and the frequency of the return signal is measured.

The theory behind the operation of an ultrasonic flowmeter is based on the concept that there is a change in the velocity of the ultrasonic wave pulses when there is a change in the flow rate of a fluid.

Portable Clamp-on Ultrasonic Flow Meter
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What are ultrasonic flow meters used for?

Ultrasonic flow meters are ideal for applications involving water-based or sonically conductive dirty process fluids. They can also measure flows of non-conductive fluids.

These flow meters can be used to measure the velocity of fluids that pass ultrasonic waves, such as water, molten sulfur, cryogenic liquids and chemicals.

Ultrasonic clamp-on transmission meters are most often used in industrial flow measurement because they are cost-friendly, smaller and more accurate. These clamp-on transducers are often used when pipelines cannot be disturbed. Because they are not in contact with the process, the meters cannot be contaminated or damaged by corrosive fluids, leaving no waste products in the pipe.

Industries that use these meters include oil and gas, water and wastewater, energy, chemical, food and beverage.

Ultrasonic Flow Meter (Doppler)
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