Paddlewheel Flow Meter: Best Velocity Flowmeters

Flow rate measurement of fluids and gases is done in many industries for safety and accuracy purposes. To get desirable flow rate readings, special kinds of instruments called flow meters are essentially used. With various fluids and processes that use fluids, different types of flow meters are dedicated to each application. Flow meters need pipes or channels to measure the flow rate of substances running through them accurately. 

Flow rate is measured in either mass flow rate or volumetric flow rate. Today, our main focus is on a particular flow meter called a paddlewheel flow meter. Since flow meters are categorized based on their working principles, it is important to pick a flow meter that suits your application needs. The five main categories that flow meters fall under include mass flow meters, differential pressure flow meters, positive replacement flow meters, and velocity flow meters. Paddle wheel flow meters fall under the velocity flow meters category. 

How Paddlewheel Flowmeters Work 

Since the paddlewheel flow meter uses the velocity flow meters working principle, it measures flow in volumetric flow rate. Volume is directly related to the fluid’s velocity when measuring flow rate. Therefore, when Reynold’s number of fluid goes beyond 10000, the paddlewheel’s sensitivity goes down. Other flow meters that use the same working principle include vortex shedding, turbine, ultrasonic, abs electromagnetic flowmeters. 

You need to understand paddlewheel flow meters as their working principle, which works mechanically to measure flow rate. This means that they don’t need any electrical energy to run, therefore, making them cost-effective. Paddlewheel flowmeters are further categorized into two groups. To measure flow rate using both kinds of paddlewheel flow meters, fluid flow needs to be there. The two kinds of paddlewheel flow meters are mentioned below:

  • Axis-flow Paddlewheel flow meter – This type of paddlewheel flow meter is built in a shape that looks like a windmill. 
  • Tangential-flow paddlewheel flow meter – The structure used to design this type of paddlewheel flow meter looks like a waterwheel.

To get the flow rate while measuring a fluid or gas, the motion brought about by the paddle wheel is directly proportional to the fluid’s flow. Therefore, the number of rotations made by the paddle from the fluid flowing inside the flow meter helps to provide reading when measuring flow rate. Inside the paddlewheel flow meter, there are impregnated magnets that are used to revolve the axis. The work of these magnets is to turn the pulses into signals with the help of the magnates fitted along the borders of the flow meter. Once the number of rotations is transformed, the flow rate will be provided.

Accurate measurement of flow rate using the paddlewheel flow meter depends on the straight pipe placed before and after the flow sensor. The components that make up the paddlewheel flow meter include the display/controller, the paddlewheel sensor, and a straight pipe. 

The magnates generate a voltage that is directly proportional to the flow of the measured fluid. The faster the flow, the higher the voltage generated. The motors fitted inside the pipe are made using various types of materials, including polypropylene, PVDF, and stainless steel. Paddlewheel flowmeters are used to measure clean fluids since they are very sensitive and can be clogged by dirt. The compatibility of other fluids besides water has to be checked first before using paddlewheel flow meters. Corrosive fluids also have to be avoided when using paddlewheel flow meters to avoid damaging the moving parts. 

The best thing about using paddlewheel flow meters is that they have simple structures that make them quite effective when measuring the flow rate of clean fluids such as water. Paddlewheel flowmeters are also easy to install and maintain. However, maintenance needs to be done frequently to ensure that the flow meter doesn’t clog. 


The need for accurate flow measurement instruments has increased in the past few years. New flow measurement technologies are coming up, while old ones are improved to enhance their efficiency. A paddlewheel flow meter is a simple yet effective flow measuring instrument. However, they are best used with clean fluids to avoid clogging the moving parts. As you plan to buy a water flow meter, ensure that you look for one that matches your application’s requirements. 


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