Alicat P Series Pressure Gauge - Manual (Page 32)

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DIFFERENTIAL PRESSURE CONTROLLERS:
The differential pressure controller is designed to change the flow to allow the
control of a pressure ratio between two points in the line. There are a variety of
applications for this device.
One of the most common is to control the difference in pressure across some
sort of element that changes resistance to flow over time, such as a filter
or one that changes area with time as would happen with orifice testing. To
accomplish differential pressure control, the controller has two sensing ports
which are piped to the upstream and downstream sides of the pressure drop in
the system.
These two ports run either to two separate pressure sensors or for low
differential pressures – they may be run to the two legs of a single differential
pressure sensor. The controller itself changes the flow to the two sensing ports
until the difference between the two pressures matches the set-point.
P2 P1
P2 P1
P2 P1
Differential Pressure Controller Application