What is a flow meter?

A flow meter is simply defined as a device used to measure the speed at which a gas or liquid is moving through a pipe.

This definition is deceptively simple, as the method with which that flow is measured varies greatly from measuring technology to application. Nevertheless, the definition is always applicable.

The basis ethos that we follow today is based on the statement from Lord Kelvin (1824 -1907) who stated ‘what you can measure you can manage’.

If we don’t measure accurately then how can we possible expect to manage accurately. To achieve this the flowmeter becomes the most important element in any measuring, monitoring or batching system.

How do flow meters work?

Unfortunately, there’s no such thing as a ‘universal’ flow meter. Every application needs to be assessed to understand which metering technology will be best.

There are essentially two measuring techniques for flow:

Volumetric

Only offered by positive displacement meters that measure the actual volume of fluid. Volumetric flowmeters are not affected by turbulent flow therefore there is no need for straight pipe lengths or conditioners. This is the best technology for low flow rates.

Velocity

Most flowmeters are velocity devices where the volume is inferred via a mechanism that measures the fluid velocity (or speed). For this technique to be accurate smooth, laminar flow is required upstream & down stream of the flowmeter which can be achieved with straight pipe length. 

Velocity Technologies Include:

• Turbine (Helical Vane, Single Jet, Multijet)
• Electromagnetic (Mag)
• Ultrasonic