Measuring the flow rate of gases or liquids requires special kinds of measurement devices called flow meters. These unique instruments measure flowing substances that run through pipes and sometimes liquids stored in open channels based on volumetric or mass flow rate. Flow meters are categorized based on their varying applications, materials used to make them, and type fluid flow. 

The five main categories of flow meters include positive displacement flow meters, mass flow meters, differential pressure flow meters, velocity flow meters, and open channel flow meters. The paddlewheel flowmeter belongs to the velocity flow meter category. 

This article discusses the paddlewheel flow sensor and how it is used in various applications. This type of flow meter is cost-effective when you want to measure the flow rate of liquids. Read along to get more insights on how the paddlewheel flow meter works. 

Velocity Flow Meter Types 

A velocity flow meter type shows a volumetric flow rate directly related to the fluid’s velocity. This type of flow meter’s sensitivity drops when Reynold’s number of fluid is greater than 10000. Velocity flow meters are further broken down into electromagnetic, vortex shedding, turbine, ultrasonic, and paddlewheel liquid flow meter. 

Working Principle & Classifications of Paddlewheel Flow Meters

The first thing you have to know about flow paddlewheel flow meters is that they function mechanically. This makes them cost-effective since they don’t require power to run. There are two groups of paddlewheel flow meters which both work mechanically. These two kinds of flow meters depend on the liquid flowing through them to measure flow rate. The two groups of paddlewheel flow meters include:

  • The tangential-flow paddlewheel flowmeter – This type of velocity flow meter is built in a structure that looks like a water wheel. 
  • Axis-flow paddlewheel flowmeter – This type of paddlewheel flow meter is structured like a windmill. 

The motion created by the paddle wheel is directly proportional to the flow of the liquid being measured. This means that the liquid flowing inside the flow meter helps to rotate the paddle, which measures the flow rate from the number of rotations made. Paddlewheel flowmeters have impregnated magnets in the revolving axis, which help turn pulses into signals, together with the magnets fitted on the border of the paddle. Flow rate is gotten by transforming the number of rotations. 

A straight pipe needs to be placed before and after the flow sensor to measure the flow rate of water or fluids using the paddlewheel flow sensor accurately. This flow meter comprises three components: the pipe, paddlewheel sensor, and the display/controller. Free rotating wheels are found inside the sensor, with perpendicularly placed encapsulated magnets placed to the flow of the fluid. 

Electric charges are generated by magnates, which are related directly to the flow of the fluid. High voltage frequencies are created when the fluid flows faster through the flowmeter. Various materials are used to make motors that are fitted inside the pipe. The motor can either be made from stainless steel, PVDF, or polypropylene. Due to its high sensitivity, the paddlewheel flow meter is used to measure the flow rate of clean water or fluids to avoid clogging the paddles. 

If you plan to use the paddlewheel flow meter with other fluids besides water, then the compatibility of the fluid needs to be checked first. The chemical composition of the fluid also needs scrutiny to avoid corrosive fluids, which may damage the moving parts of these types of flow meters. 

Pros of Using the Paddlewheel Flow Meter

With a simple structure, the paddlewheel flow meters are quite effective when measuring liquid flow rate. Installing these types of flow meters is also pretty easy, and they also require low maintenance. Its compact design is quite reliable when it comes to measuring huge amounts of water or fluids cheaply. It is an ideal flow meter for measuring gravitational flow because it has no pressure drop. 

The maintenance cost is quite low. However, it has to be done frequently if you want to keep up with the high accuracy measurement. The paddlewheel flow meters are used to regulate output in chemical metering pumps. You can also use a paddlewheel flow meter to alert users of flow fluctuations outside the pre-set parameters. 


With different types of fluids and gases used in various flow processes, flow measurement accuracy is paramount for the safety of users and the quality of the product. Paddlewheel flow sensor types are very easy to install, maintain, and also easy to use when measuring the flow rate of clean liquids such as water. If you want to get value for your money, you need to look for flow meters that match your application. If you are unsure of the application, you need to ask for the manufacturer’s guidance on using it.