MKS 640A/641A, Manual, Page: 29 / 88

Gas Pressure and Control Chapter Two: Installation
16
Downstream Pressure Control
Gas Flow
Controlled
Volume
Figure 1: Downstream Pressure Control
The 640 Series controllers are shipped from the factory configured for downstream pressure
control. Refer to Table 8, page 31, for the initial configuration of the unit.
Upstream Pressure Control
Upstream pressure control occurs when the 640 Series controller is positioned after the
controlled pressure volume in the gas flow path, so that the controlled volume is upstream of the
640 Series controller. The gas from the pressure system enters the controller on the transducer
side, labeled “Controlled Pressure Port.” Figure 2 shows the gas flow for upstream control.
Gas Flow
Upstream Pressure Control
Controlled
Volume
Figure 2: Upstream Pressure Control
The 640 Series controllers are shipped from the factory configured for downstream pressure
control. To configure the pressure controller for upstream control, you must reposition jumpers
inside the unit. Refer to How To Select Upstream Control, page 51, for instructions.