Paddle wheel flow meters consist of three primary components: the paddle wheel sensor, the pipe fitting and the display/controller. The paddle wheel sensor consists of a freely rotating wheel or impeller with embedded magnets which is perpendicular to the flow and will rotate when inserted in the flowing medium.
Principle of Paddle Wheel Flow Meters
As the magnets in the blades spin past the sensor, the paddle wheel meter generates a frequency and voltage signal which is proportional to the flow rate. The faster the flow the higher the frequency an
d the voltage output.
Paddle Wheel Flow Meter Advantages
- Low cost solution with high flow system accuracy
- Easy to install and operate, resulting in a low cost of ownership
- No pressure drop making it ideal for gravity flows
- Insertion flow meter design lowers installation and maintenance costs
Paddle Wheel Flow Meter Limitations
- Paddle wheel meters work best with clean fluids as particulates can prevent the paddle from spinning properly
- Not suitable for gases
- Requires a turbulent flow profile (consistent fluid velocity across the pipe diameter) for accuracy
- Requires a straight run of pipe before and after the flow meter to allow swirl patterns in the flow stream to dissipate
- Paddlewheel meters may not function properly with high viscosity fluids where the flow profile is laminar
- The pipe must be full; any air in the line may lead to inaccuracies
Typical applications for paddle wheel flow meters include the accurate measurement of preset fluid volumes in dispensing systems, control of chemical metering pump output, flow verification, irrigation systems and alerting users to flow rate increases or decreases outside a programmed range.
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