Positive Displacement Meters: Pros, Cons and Selection

Positive displacement flow meters, sometimes known as PD meters, have been around for more than 100 years. They are commonly used in a wide range of applications, from domestic water measurement to measuring ultra flow rates of chemicals at high subsea pressures.

First off - what is a 'positive displacement' meter? Well, as the name suggests it involves the positive displacement of a volume of fluid - this is usually a liquid but there are some units suitable for gas. There is a chamber and inside the chamber, obstructing the flow, is a rotor.

The shape of the rotor and chamber vary greatly with each meter type but they all provide an output for each rotation. Most meter designs therefore lend themselves to being totalisers. Most can have the flow rate calculated from this primary data.

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