The 4 water flow meter types – which is right for your organisation? | Electronics Maker

There are plenty of reasons why you might want to measure the way in which liquids, gases or another materials flow, and for every single one of those reasons, your organisation will need a flow meter.  You can also pick one up at any high-quality supplier e.g. RS Components. However, ‘flow meter’ is a phrase like ‘work clothes’ or ‘sports shoes’ – and we all know there’s a big difference between an astronaut’s suit and boots and a construction worker’s high-viz gear.

Indeed, there’s an awful lot of flow meters out there: ones that measure mass; others that measure volume.  There’s electromagnetic flow meters for conductive liquids, and capillary flow meters that rely on the principle of gas heat transfer.  Vortex shedding meters use vortices, ultrasonic meters rely on sonar-like ultrasound, and the list goes on and on.

In this piece, we’re going to be discussing water flow meters, which are specifically designed for water or water-like liquids.  And just like all of those other flow meter types, not every water flow meter is created alike.  In fact, there are four main types of water flow meter, and they are all unique in the basic working principles, benefits and costs that make them suitable for their highly-specific applications:

1. The mechanical water flow meter

The most affordable, common and simple of the water flow meter types is the mechanical version, which is often referred to as a turbine flow meter.  That’s because it does its measuring with the use of a rotating turbine or propeller, which is a highly effective way to measure the speed of flowing water through a pipe.  Basically, the turbine blades rotate at exactly the same rate as the water that is flowing.

However, because the meter has mechanical moving parts, the presence of dirty water or liquid will ramp up the maintenance cost and frequency and drive down the reliability.  Another issue is that the turbine may not rotate correctly when the water flow is very low.

2. The vortex water flow meter

Another way to measure water flow is with a more sophisticated vortex meter, which operates with the help of a sensor that creates vortices or ‘swirls’ in the liquid which are then turned into proportional frequency outputs.

A big benefit of vortex meters is that they can measure not just volumetric flow, but also mass flow.  Some types will also provide measurements for pressure, temperature and density.

3. The ultrasonic water flow meter

Next up, we have the ultrasonic water flow meter, which works much more like the sonar on a submarine than the simple paddle-wheel of a turbine meter.  In the ultrasonic meter, one ultrasonic pulse is sent downstream, and another is sent upstream – and the difference between the time it takes for the two different pulses to reach their targets is used to calculate how fast the water is really flowing.

Crucially, ultrasonic meters don’t actually need to be inside a pipe to function.

4. The magnetic water flow meter

Finally, let us introduce you to the magnetic flow meter, which exists in the world thanks to a 19th century physicist by the name of Michael Faraday.  He discovered the principle of magnetic induction, which allows the magnetic flow meter to measure the speed of flow with the help of a magnetic field.  Faraday’s Law is the notion that as liquid flows through a magnetic field, voltage is produced – and the faster or slow it is flowing, the more or less voltage is proportionately created.

The big downside to using magnetic fields to measure water flow, however, is that they require conductive liquids – and pure water is not among them.

Hopefully, this summary of the four main types of water flow meter will help guide your selection, based on your specific goals, requirements, conditions and budget.  The flow meter you need will depend on the monitoring site, the water type (and presence of contaminants), the temperature, the basic flow speed (ie. very fast or very slow), the pressure, pipe diameter, and a range of other variables.  Getting the selection spot-on will mean optimal performance, reliability and cost-effectiveness, so always discuss your requirements with an industry expert prior to purchase and set-up.