Paddle Wheel Flow Sensor Technology And Use

Paddle Wheel Flow Sensor Technology and Use

The effectiveness of liquid flow processes and flow systems depend largely on the type of water flow switch or flow sensor used. These are essential instruments that offer accurate flow measurements of various kinds of fluids and gases. However, the type of flow meter or sensor determines the effectiveness of flow accuracy in any application. Among the many types of water flow meters is the paddlewheel flow meter. This type of liquid flow meter offers effective readings when measuring the flow rate of different fluids. 

This post focuses on paddlewheel flow meter and their effectiveness when it comes to different fluid flow measurements. Read along for a better understanding of how this type of flow meter operates. 

Paddlewheel Water Flow Switch 

A paddlewheel flow meter belongs to a category of flow meters called velocity flow meters. This category of flow meters measures flows rate by providing readings in volumetric flow rate. The velocity of the fluid is directly proportional to the volume flow rate. When measuring flow rate, the sensitivity of the paddlewheel flow meter will drop if the Reynold number goes beyond 10000. Examples are electromagnetic, vortex shedding, ultrasonic, vortex shedding, and paddlewheel flow meters. 

Understanding how different types of flow meters operate is essential for the proper utilization of these flow measuring devices. It is also essentially relevant for the proper installation of such devices. Paddlewheel flowmeters are distinguished by the type of materials used to design them. They can either be made from stainless steel or plastic. Paddlewheel flow meters can also be distinguished by detecting or evaluating signals, which can either be through an HT coil sensor, hall sensor, coil sensor, or optical sensor. 

Since there are various kinds of paddlewheel flow meters, here are a few examples and how they operate:

Paddlewheel Water Flow Switch Types and Applications 

Inductive Detection and Pulse Output

This type of paddlewheel flow sensor is made from plastic, and it is also called a PVDF or a PP paddlewheel. It comes fitted with rotating magnets, molded permanently along the arms. With precision, the magnets spin on two ceramic bearings and a resistant ceramic spindle. Magnetic fields from the spinning paddle wheel are detected outside the fluid flow area. From each revolution, two output signals are generated. Frequency changes are determined proportionally by the speed of the rotation. An integral electronics board is used to convert the signal into a square-wave frequency signal. 

Inductive Detection and Sinusoidal Output 

These flow meters are also made from plastic and are also called PP or PVDF paddlewheel flow meters. In each arm, there are four spinning magnets, molded permanently. It also comes with a ceramic spindle and two ceramic bearings that are wear and tear-resistant. The function of these two components is to help the paddle wheel spin with precision. In addition, a ferrite core coil is put outside the fluid’s flow area to detect the magnetic field from the rotating paddle wheel. 

The frequency changes based on the revolutions generated, which are proportional to the rotational speed. The rotation of the paddle generates a sinusoidal voltage signal. The coil’s voltage signal is directly proportional to the measured volumetric flow rate. Since this type of paddlewheel flow meter is two wired, extra auxiliary power is unnecessary. To allow voltage dependency, a battery-operated display unit is connected.

Optical Detection and Pulse Output  

Made from PVDF material, the optical detection and pulse output water flow switch consist of two ceramic-made bearings and a spindle to make them resist wear and tear. Two infrared receivers and transmitters in an electronic housing outside the fluid flow area. Plastic material is used to separate them since it allows infrared radiation to pass through. The infrared radiation diodes detect paddlewheel rotation. Integrated electronics are used to convert reflected I-Signal into a square wave frequency signal. Volumetric flow rate reading is directly proportional to the square wave frequency signal. 

The ferromagnetic particles found in the flowing fluid in this optical type of liquid flow meter are used to detect the flow rate. The fluid flow direction is also detected by these particles found in flowing media. 

Stainless Steel Inductive Detection and Pulse Output 

Made from stainless steel, these types of paddlewheel flow meters have very low ferromagnetic characteristics. The spindle in this type of paddlewheel flow meter is made from high-tech ceramic or stainless steel. The bearing is made from PEEK or ceramic. Inside the top-mounted electronics is an HT coil with permanent molded magnets. Electronics are also found in the HT coil that converts a coil signal into a square wave frequency signal. 


Paddlewheel flowmeters are the best kinds of velocity flow meters that make ideal instruments for measuring clean fluids such as water. However, using these water flow switch types to regulate any other fluid besides clean water may lead to inaccuracies. Since paddlewheel flow sensors have moving parts, using dirty fluids that have particles or debris may damage them and cause flow measurement errors. Corrosive fluids may also damage the moving parts. 

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