Ultrasonic Measurement Technology: Noncontact Flow Metering

Piezo Sensors Work by Different Metering Principles

The measurement of propagation time and the so-called Doppler effect are the two fundamental metering processes in noncontact ultrasonic flow rate metering.

For propagation time measurements, two piezo transducers operate as transmitter and receiver while using the direct and indirect piezoelectric effect. They are positioned in a sound path oblique to the direction of flow and measure the sound propagation time in and against the direction of flow. The flow velocity can be determined from the difference in the sound pulse propagation time.

Due to the Doppler effect, when an ultrasonic pulse has been emitted the ultrasonic waves are scattered or reflected on liquid particles. The frequency shift between the reflected wavefront emitted and received by the same piezo transducer is proportional to the flow velocity.

 

  • Noncontact meterings
  • In-situ meterings

 

 

  • OEM products
  • The piezo elements used are produced on a large scale, thus keeping costs down

 

 

 

 

Flow Metering with Piezo Sensors

In many areas, metering the flow rate is fundamental for controlling processes. In modern building services, for example, the consumption of water, hot water or heating energy is recorded, thus controlling both supply and billing. In industrial automation and especially in the chemical industry, volume metering can replace the weighing of substance quantities. Not only the flow velocity, but also the concentration of certain substances can be detected. The propagation time measurement and the Doppler effect are methods also used in >> medical technology, e.g., in sonography or in the measurement of the blood flow velocity.

Piezoelectric Ultrasonic Transducers for the Detection of Gas Bubbles

The undisturbed flow of a medium without air or gas pockets is often required in metering or bottling systems. One method of bubble detection is the propagation time measurement by ultrasonic technology. Two piezoelectric ultrasonic transducers work as transmitter and receiver. The sensor performs noncontact detection of air and gas bubbles in the liquid through the tube wall, and thus allows continuous quality monitoring. Examples of industrial applications include control technology, such as the monitoring of dosing and filling machines.

  • Flexible, compact designs: Rings, disks, small plates
  • Variable strokes, high force generation and acceleration
  • No friction, no maintenance, no wear
  • Cost-effective: Large-scale piezo element production
  • No Contamination of the Measuring Medium

 

In the field of >> medical technology, the ultrasonic-based gas bubble detection can be used for example, for monitoring dialysis and heart-lung machines.

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