Appendices
January 2023
•
Rev. 0
• Standard Devices User Manual
46
Back Pressure Control
When the valve is located on the downstream side (inverse control), the sensor controls pressure upstream. This configuration
is referred to as a back pressure controller. This configuration follows our inverse pressure control algorithm. The valve closes to
increase pressure, and opens to decrease pressure.
✓
Note:
Back pressure controllers include “DS,”
for downstream valve, in their part codes.
Dual Valve Pressure Control
The port on the face of the PCD unit is connected to the closed volume you want to control pressure in. The valve on the supply
side opens to increase the pressure in the closed volume, and the valve on the exhaust side opens to decrease pressure.
Differential Pressure Control
Differential pressure controllers have two ports for connecting to points in the system where the differential pressure is measured.
The upstream port is for the higher pressure, and the downstream port is for the lower pressure. In these devices, the differential
pressure ports have no flow and are not connected to the flow path. A PCD-Series is used in closed volume applications.
Gas Supply
Pressure Regulator
Pressure Controller
Process
Flow Exit Port
Downstream Valve
Gas Supply
or Atmosphere
Alicat
Controller
Pressure
Regulator
Flow in both directions
Closed Volume
at Setpoint Pressure
Exhaust to
Vacuum or
Atmosphere
Gas
Supply
Alicat
Controller
Flow
Exhaust
Process line
(port is in the back of the unit)
P1 Sensor
(no flow)
P2 Sensor
(no flow)
Process/Device under Test
P1
P2
Pressure
Regulator
15PSID pressure controller
with two differential pressure
detector ports in front and
a DB-9 serial connector.
