FAQ Ultrasonic Doppler Flowmeter

1. How does a ultrasonic doppler flowmeter work?
A high frequency signal is projected through the wall of the pipe and into the liquid. The signal is reflected off impurities in the liquid such as air bubbles or particles, and sent back to the receiver. The frequency difference between the transmitted and received signal is directly proportional to the fluid's flow velocity.

2. Can I use a ultrasonic doppler flowmeter with particulates?
Yes. In order to use a ultrasonic doppler flowmeter, the liquid must have particulates or bubbles. Most require a minimum size of 25 ppm or 30 μm; check with each ultrasonic doppler flowmeter for specific particle size requirements. if clean liduid without particulates, you could choose EU-108 ultrasonic flowmeter. For the river flow, you could choose GE-104D doppler flowmeter.

3. Some flowmeters measure in velocity (ft/sec). How can I convert the readings to volume/time?
GPM= 2.45 * (ID in inches)² * (VELOCITY in ft/sec)

GPM= gallons per minute
ID = inside diameter of the pipe in inches.
This formula is for water—it does not consider viscosity, temperature, or pressure. However, temperature, viscosity, and pressure will not effect a ultrasonic doppler flow reading.

4. What if my fluid is not water?

The speed of sound through water is approximately 1470 ft/sec. Most instruments are calibrated for that rate. Other fluids may be used, but your instrument should then be recalibrated.

5. Will pipe insulation/thickness affect my reading?
Yes. Insulation should be removed before mounting the sensor.

6. Must a ultrasonic doppler flowmeter be permanently installed?

No. Because ultrasonic doppler flowmeters measure flow externally, most can be easily removed and moved from site to site.

7. Does a ultrasonic doppler flowmeter require a minimum upstream straight pipe length?

Yes. ultrasonic doppler flowmeters require ten pipe diameters from any valve, tee, bend, etc. ultrasonic doppler flowmeters also require a full pipe flow.

8. What are the advantages of using a ultrasonic doppler flowmeter?
—good for slurries, aerated liquids


9. What are the limitations of using a ultrasonic or doppler flowmeter?
—Ultrasonic is suitable for clean liquids
—doppler mainly for not clean liquids or river
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