Apex Digital PC - Applications; Forward (Downstream) Pressure Control; Back Pressure Control; Changing the Valve Orientation

8 Getting Started
Applications
Forward (Downstream) Pressure Control
When the valve is located on the upstream side (direct control), the sensor will control
pressure downstream. This configuration follows our standard pressure control algorithm.
Note: the valve opens to increase pressure, and closes to decrease pressure.
Example:
Gas Supply Pressure Regulator Pressure Controller Process Flow Exit Port
Upstream Valve
Back Pressure Control
When the valve is located on the downstream side (inverse control), the sensor will control
pressure upstream. This configuration is referred to as a back pressure controller. This
configuration follows our inverse pressure control algorithm. Note: the valve closes to
increase pressure, and opens to decrease pressure.
Example:
Gas Supply Pressure Regulator Pressure ControllerProcess Flow Exit Port
Downstream Valve
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Note: Back pressure controllers include “DS,” for downstream valve, in their part codes.
Changing the Valve Orientation
The valve position on your pressure controller can be switched in the field. The controller
must also be configured for either forward pressure control (direct control) or back pressure
control (inverse control). If you need to switch from forward to back pressure control, contact
support (page 16).
Dierential Pressure Control
Dierential pressure controllers have two ports for connecting to the points in the system
where the dierential pressure is to be measured. The upstream port is for the higher
pressure, and the downstream port is for the lower pressure. In these devices, the dierential
pressure ports have no flow, and are not connected to the flow path.