Paddle Flow Meter, Paddlewheel Flowmeters

A paddle flowmeter (also known as a paddlewheel flow meter) uses a completely different way to determine the amount of fluid flow than the pressure differential flow meter. This type of sensor has a paddlewheel that is placed directly in the fluid flow so that it can rotate freely as the fluid passes it. The faster the fluid flows past it, the faster the paddle wheel rotates. Each paddle or web of the paddlewheel has a magnet mounted in it so that a sinusoidal waveform is produced when it passes the detector mounted in the head of the sensor. A frequency-to-voltage converter is used to convert the sine wave signal to a variable-voltage signal. It should be noted that in order for a paddle flowmeter to measure properly, it must be mounted in a straight run of piping where he flow will be laminar. The paddlewheel is a low-cost sensor used in applications that don't require a high degree of accuracy.

The paddle-wheel flowmeter belongs in a category of flowmeters called Velocity Flow Meters. Velocity flow meters use the change in velocity (speed) that occurs when fluid flow changes to measure the amount of flow. Velocity meters can be used in systems that are not adversely affected by changes in viscosity. Examples of velocity flow meters include the paddlewheel flowmeter, the turbine flowmeter, the vortex flowmeter, the electromagnetic flowmeter, and the ultrasonic (Doppler) flow meter.

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