What is a flow sensor and what does it do?

The efficient running of water treatment systems, Industrial washing systems or even just our air conditioning at home is due in the main part to many measuring and monitoring devices. The management of what are sometimes, very complex systems is made much easier with the correct combination of sensors and indicators.

One key function that needs to be measured is the amount of liquid or gas passing through these systems. To do this, a simple device called a flow sensor is used.

What is a flow sensor?

A flow sensor is also known as a flow gauge or liquid meter. They can measure rates of flow within a pipe and, when combined with one or more flow switches, can be used to control that flow.

Flow sensors are, in principle, simple devices. They consist of a transducer which measures the flow of the liquid, gas or vapour flowing through the pipe and a transmitter which delivers an output signal to a monitoring system or alarm.

Despite being a simple device, there is more than one type of flow sensor, each with its own advantages and disadvantages.

Paddlewheel flow sensors.

One of the most common types of the flow sensor is the paddlewheel sensor. They are connected to the pipe, and flow is measured and calculated according to how fast the paddle is turning. Due to its simplicity, this type of sensor can be used for a variety of purposes, especially large capacity measurement.

This type of sensor, however, requires a high level of maintenance due to wear on the moving parts and has a risk of clogging depending on the type of liquid or gas being measured.

Other types of flow sensors.

Rota flow meters, also known as Variable Area Flow Sensors, are another type of flow sensor that is commonly used, this time because of its simple tube and float design. The simple linear output means it is often used to measure the flow of fluids and gases.

For a greater range of output, magnetic-inductive sensors detect volumetric flow quantity, consumed quantity and medium temperature. While this last type of sensor seems to cover all of the functions that are likely to be required, it is not the most commonly used sensor for a variety of reasons.

Selecting the right flow sensor.

This is because there is no one type of flow sensor that will suit every purpose. Every installation will have its own requirements due to many factors. 

As well as any installation requirements and budgetary constraints, other things to be considered include the level accuracy and type of output required. This even is before more normal considerations like durability and reliability are taken into account and whether the flow sensor is to be used for a common purpose like water treatment or something more unusual. 

With all of these different variables, it is easy to see that different combinations of sensors and switches are often required to monitor all but the simplest of applications.

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