Difference between Differential Pressure Flow Meter and Positive Displacement Flow Meter

industry piping

Differential pressure (DP) flow meter and positive displacement (PD) flowmeters are two type of flow rate measuring device. They are worked on a different principle. To know more about these flow meter, please read.
- Differential Pressure Flow Meter Working
- Positive Displacement Type Flow Meter

Here is the quick comparison between DP flow meter and PD flow meter

Differential Pressure Flow Meter
Positive Displacement Flow Meter
The indirect method of measurement. To find flow rate they use Bernoulli’s principle of conservation energy

Flow rate measured directly in volumetric unit
There is no need of mechanical movement of component (no moving parts). Differential pressure head typically measured by using pitot tubes, manometer.

There is a mechanical movement of component of measuring device.
Measure pressure drop across a restriction in passage of fluid

Entrap and release fixed amount sample fluid
Used for low viscous fluid
Used for high viscous fluid, less accurate in low viscous fluid

It cannot use for low flow rate
It can measure low flow rate

Need long straight pipe in upstream and downstream to accurate measurement

No need of long straight pipe in upstream and downstream.
High sensitive to uneven flow(pulsing)
Little sensitive to pulsing

High turndown ratio

Venturi meter,Orifice meter, Dall tube etc
Oscillating piston, Nutating disc, Rotary Vane etc

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