Positive displacement meter

Positive displacement (PD) flow meters measure the volumetric flow rate of a moving fluid or gas by dividing the media into fixed, metered volumes (finite increments or volumes of the fluid).

These devices consist of a chamber(s) that obstructs the media flow and a rotating or reciprocating mechanism that allows the passage of fixed-volume amounts.

Complete sensor systems provide additional capabilities such as an integral display and/or user interface.

For both types of positive displacement flow meters, performance specifications include the minimum and maximum measurable flow rate, operating pressure, temperature range, maximum allowable material viscosity, connection size, and percent accuracy (typically as a percentage of actual reading, not full scale).

Thanks to screw meters, public and independent institutes of metrology worldwide can compare their respective work, facilities, or calibrate other flowmeters (e.g., master metering) or compare flowmeters' performance according to different measurement principles.

By tracking the movements of the spindle, the flow meter determines the number of times the chamber traps and empties fluid.

They are widely used in the custody transfer of oils and liquid fluids (gasoline) and are applied on residential home natural gas and water metering.

Meters that rely on a liquid seal create a relatively low pressure drop.

Because of their high accuracy, PD meters are widely used at residences to measure the amount of gas or water used.