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How to choose the correct flow meter


Before you can make the right choice, you need to know what a flow meter is. A flow meter is an instrument that is used to measure the amount of liquid, gas or vapor passing through the indicator. Flow meters can also be known as flow indicators, flow gauges or liquid meters. The meters go by different names because they could be used for multiple purposes.

How does a flow meter work

How a flow meter works depends on how the measurement is displayed. But all flow meters work on the same principle. Flow creates movement in the instrument, such as a ball or paddlewheel spinning, so the flow can be measured. If there isn’t a moving mechanism, there will be a transparent or glass tube through which you can check if there is a flow. That’s when you call it a flow indicator, it gives an indication of the flow. The advantage of a moving mechanism is that they can be read from a further distance.

A flow meter can, for example, be used as time measuring units (these measure flow rates over a set time). They can also be totalising flow meters that continually measure the medium passed through.

Types of flow meters

Flow meters can have different applications and measurement techniques. The most important meters are discussed below.

The most commonly used types of flow meters are paddlewheel or turbine flow meters. Paddlewheel meters are connected to a process with the liquid passing through and turning a paddle wheel. The primary device calculates the speed as the paddle is turned. This simple structure is compact and can perform a large-capacity measurement.

Electromagnetic flow meters work according to Faraday’s law of induction. According to Faraday’s law, a conductor placed in a magnetic field generates an electric voltage proportional to its speed. Electrical voltage can be generated based on electromagnetic induction because a conductor moves in the magnetic field. In a flow measurement, the liquid becomes the conductor, so the higher the flow rate, the higher the generated voltage.

The bypass flow meter consists a bypass chamber, which is laterally connected to a tank as a communication tube with two connections. Due to this connection, the level in the bypass chamber corresponds to the level in the vessel. The float with built-in permanent magnet system, assembled in the bypass chamber, indicates the liquid level by the magnetic display assembled on the outside of the bypass chamber.

A Coriolis flow meter contains a tube that is supplied with a fixed vibration of energy. When liquid passes through the tube, it will cause a change in the vibration of the tube. The tube will rotate and the phase difference can be measured. A Coriolis flow meter provides accurate information about liquids or gases flowing through a pipe.



Flow measurement are used in a wide variety of applications including measuring of boiler fuel oil and diesel oil, as well as for transactions for kerosene, light oil and heavy oil. There are totalizing or current flow options available in a wide range of flow volumes, with different connections available to suit the process. Totalizing flow meters show the total volume of the liquid that has passed through the flow meter since the start of operations. Current flow meters indicate the flow through the instrument in the current moment. Both versions come with temperature sensing options to also measure the temperature of the liquid flowing through the flow meter.



Water flow meters are used to measure the volume of water used. Water meters may also be used at water sources or throughout the water system to calculate the flow rate of a part of the system. Water flow meters may also measure the flow rate of slurries or fluids in closed pipes. The flow rate of water is measured in cubic metres (m3), litres per minute of litres per hour on an electronic or mechanical register.


Service of Flow meters

GMS Instruments is a specialised and authorised maintenance partner of a.o. Aqua Metro. This means that all our service technicians are properly trained and educated by the manufacturer before handling your instrumentation. Because we are an authorised maintenance partner of leading manufacturers, we can keep a large stock of original spare parts. By continuing a large inventory of original spare parts, we can react correct and swift at your service requests. All our service technicians are well trained to perform repairs on site, to minimize downtime for your process.

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