Ultrasonic Flow Meters

An ultrasonic flow meter is an instrument that measures flow by detecting the action of a fluid flow on an ultrasonic beam (or ultrasonic pulse). It is a volumetric flow meter that requires the presence of air bubbles or tiny particles in the liquid stream. These meters are suitable for wastewater applications and, that’s the reason they are ideal for applications that require chemical compatibility, low maintenance and low pressure drop.

Working Principle of Ultrasonic Flow Meters

Transit time method

In this method, two sensors transmit ultrasonic pulses to each other through the fluid. One pulse travels downstream and is faster, while the other travels upstream and is slower. The difference in the transit times between the two pulses is measured, and this difference is directly proportional to the fluid’s velocity.

Doppler Method

The other method is the Doppler method, which is used for liquids with suspended particles or gas bubbles. An ultrasonic signal is sent into the pipe, and the sound waves reflect off these discontinuities. The frequency of the reflected sound waves is shifted based on the velocity of the moving particles, a principle known as the Doppler effect. The magnitude of this frequency shift indicates the flow rate.

Key Features of Ultrasonic Flow Meters

Have a look at these features of an ultrasonic flow meter:

• Non-invasive Measurement: Clamps onto the outside of the pipe, preventing contamination or pressure loss.
• High Accuracy: Provides precise measurements for both low and high flow rates.
• Bidirectional Flow Detection: Measures flow in both directions for enhanced monitoring.
• Wide Range of Pipe Sizes: Suitable for small to very large diameter pipes.
• Low Maintenance: No moving parts, reducing wear and tear and lowering maintenance needs.
• Versatility: Compatible with various liquids, including water, chemicals, and wastewater.
• Easy Installation: Can be retrofitted to existing systems without major modifications.

Applications of Ultrasonic Flow Meters

Routine applications of ultrasonic flow meters include the following:

• These meters are used in wastewater and dirty liquid applications
• These meters are used where chemical compatibility, less maintenance and low pressure drop are required.
• These meters are used to analyse volumetric flow by measuring the velocity of a liquid through ultrasound.
• These meters measure the difference between the propagation time of an ultrasonic pulse and the direction of liquid flow
• The applications of these meters range from process to supervisory processes
• This is a device used for volume flow measurement of liquids and gases.
• These are an excellent alternative to vortex flow meters and electromagnetic flow meters.

Benefits of Ultrasonic Flow Meters

Benefits of an ultrasonic flow meter include:

• It does not block the path of liquid flow
• The o/p of the meter varies depending on the density, viscosity and temperature of the liquid
• The flow of the liquid is bi-directional
• The meter has a good dynamic response
• The meter’s output is in analogue form
• Energy conservation
• Suitable for large mass flow measurements
• Easy to install and maintain
• Very good versatility
• No contact with liquids
• No risk of leakage
• No moving parts, pressure loss
• High accuracy