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General Information on the Ultrasonic Flowmeter

Principles of operation


The basic principle of this flowmeter employs the frequency shift (Doppler Effect) of an ultrasonic signal reflected by suspended particles or gas bubbles (discontinuities) found in liquid flow.

These non-invasive Doppler ultrasonic flowmeters measure liquid flow from the outside of full pipes. A typical system incorporates a transmitter w/totalizer and a transducer. The transducer is mounted to the exterior of the pipe. An ultrasonic signal, generated by the transmitter, is emitted through the transducers into the flowing liquid and is then reflected back by the discontinuities. The transmitter measures the difference between the output and input frequency and converts the frequency difference into electronic pulses. These pulses are scaled and totaled for flow quantity. Both portable and dedicated transmitter/display units are available.

In clean fluid applications where insufficient particles or bubbles exist, the transducers are mounted at a point in the piping where non-symmetrical turbulence will be experienced. This is done by simply mounting the transducers after a 90 degree pipe elbow. In this case, the reflections are from the local turbulence of flow caused by the pipe configuration. The electronics include digital filtering and recognition circuitry to reshape the distorted signal into an ideal model, providing a usable linear measurement.


Typical applications: Sewage, sludge, slurries, paper stock, paper pulp, petrochemical, caustic, acids, additives, wastewater, and many other liquids commonly found in plants.

Requirements:
A minimum of 25 ppm of solids or bubbles, of 30 microns or larger. On clean water service an elbow is required. A full pipe is needed.

Things to Avoid:
Rubber, copper, cement, brass and nickel alloy piping materials. All piping materials that will absorb the ultrasonic signal.


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Controls Warehouse  •  356 Cypress Road  •  Ocala, FL  •  34472 •  Phone: (352) 687-0351