Difference between Fixed Area & Variable Area FlowMeters

In this article, you will learn the difference between a fixed area flow meter and a variable flow meter.

Difference between Fixed Area and Variable Area Flow Meters

With orifice plates flow meters

• As the rate of flow increases, so does the differential pressure.
• By measuring this pressure difference it is possible to calculate the flow rate through the flow meter.
• The pass area (for example, the size of the hole in the orifice plate) remains constant.

With any type of variable area flow meter

• The differential pressure remains almost constant as the flow rate varies.
• The flow rate is determined by the position of the float.
• The pass area (the area between the float and the tube) through which the flow passes increases with increasing flow.

Source: spiraxsarco

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