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Measuring principle

A moving object causes changes in sound frequency. The Doppler flowmeter uses the principle of the Doppler frequency shift caused by sound scattered or reflected fromt he moving particles in the path of flow. It transmits a continuous sonic wave inclined at some angle to the flow. Small inclusions of bubbles, solids, or eddies in the flow would reflect or scatter the sound back to a receiver. If there is any movement of the inclusions, a Doppler-shift would appear in the frequency of the returned signal. The difference the transmitted and received frequencies is proportional to the motion of the flow.
Governing equation:

Vdavg is unknown here and by measuring fd, Vdavg can be calculated.
There are three types of Ultrasonic Flowmeters. The principle of operation of each type is dependent upon the speed at which high frequency sound propagates. One type of ultrasonic meter is based on the Doppler-shift or the phenomenon in which the wavelength of an approaching sound source is shorter than the wavelength of that same source as it is moving away. The transducer emits a sonic beam into the process and entrained particles or bubbles reflect the beam back to the transducer. The measured difference in the wavelengths (transmitted verses reflected) is proportional to the process' velocity. These meters are used on closed full pipes and the transducer may be mounted either on the outside of the pipe or inserted (hot tapped) into the pipe.

Application guidelines

MACE Doppler ultrasonic flowmeter is widely used in industry, water conservancy, irrigation, etc., for full pipes, partially full pipes & open channels flow measurement.

Product list
  • Doppler ultrasonic velocity sensor This sensor is used to measure velocity only in full pipes when access to the pipe is available and the pipe can be emptied when installation or maintenance is required. It can also be used in partially full pipes or open channels in situations where the user is measuring depth by a third party or ultrasonic depth sensor.

  • Doppler ultrasonic insert velocity sensor Insertion sensors measure velocity only and require access to the outside wall of the pipe in which the sensor is to be mounted.

  • Doppler ultrasonic area/velocity sensor

    This sensor is used in open channels or pipes that run partially full. This sensor is used to measure depth (using a capacitive pressure diaphragm) and velocity. Access to the monitoring point is required for installation and maintenance.

  • AgriFlo series of Doppler ultrasonic flowmeter

    The AgriFlo XCi can be used to monitor vital farm equipment and on-farm sensors. Use the versatility of AgriFlo XCi to monitor inputs as diverse as: irrigation flows; farm wastewater flows; water quality; dam levels; soil moisture; pump and engine management systems.

  • FloPro series of Doppler ultrasonic flowmeter

    The FloPro XCi can be used to monitor just about any water quantity and quality sensor together with vital mining, municipal and industrial equipment and assets. Whether you need to measure flow as well as conductivity, pH and rainfall or utilize a downward looking ultrasonic depth sensor to measure pond levels the FloPro is fully expandable to your needs. Furthermore, FloPro is easily interfaced to SCADA/telemetry systems.

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