Flow ComputerFlow Measurement

The Wave Machine: Advantages of Ultrasonic Flow Meters

An ultrasonic flow meter uses ultrasound to measure the velocity of liquid flow in order to determine the volume of the liquid flow.  

How Ultrasonic Flow Meters Work

Ultrasonic transducers are clamped onto the external surface of a pipe and generate ultrasonic pulses (sound waves) through the pipe. The liquid flow inside the pipe creates time differences in the pulses, which are examined by the flow meter to calculate the accurate flow velocity of the liquid and consequently the volumetric flow rate. 

The acoustic properties of the liquid that the flow meter is measuring can be affected by temperature, density, viscosity and suspended particles, depending on the flow meter used.

Applications of Ultrasonic Flow Meters

Ultrasonic flow meters are ideal for any dirty liquid that is conductive or water-based, such as wastewater, molten sulphur, cryogenic liquids and chemicals. They are not ideal for clean water, such as distilled or drinking water, where aerations (passing air through liquid) are better. Ultrasonic flow meters are great for applications where low pressure drop, chemical compatibility and low maintenance are required. The marine, nuclear and power industries find the clamp-on transducers especially useful because the piping is not disturbed.


  • The electronics of the ultrasonic flow meter compensate and adapt to changes in flow profile, type of liquid and pipe material.
  • Ultrasonic measurement is a more direct method of determining flow rates than other systems.
  • They are often inexpensive to use and maintain because there are no moving parts, compared to mechanical flow meters.
  • As they do not obstruct the liquid flow they can be used for sanitary, corrosive and abrasive liquids.

One piece of advice – before you expect an accurate measurement be sure that the fluid can adequately conduct ultrasonic waves to penetrate the flow stream between the transducers, otherwise the flow meter will not measure the flow rate.

Other Flow Meters:

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Coriolis Flow Meters