MKS 640A/641A, Manual, Page: 18 / 88

Chapter One: General Information Introduction
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Chapter One: General Information
Introduction
The 640A Series Pressure Controllers include the Type 640 absolute pressure controller and the
Type 641 gage pressure controller. The 640 Series Controllers consist of a Baratron®
capacitance manometer (either absolute or gage pressure), a normally closed proportional control
valve, and closed-loop control electronics. The closed-loop control circuitry enables the unit to
function as a proportional-integral (PI) controller. The unit’s compact size and small, three-inch
footprint reduce space requirements.
The 640 Series offers a variety of options including the seal material, full scale range, and
calibration. The seal material is available in an elastomer (Kalrez®, Viton®, Kel-F®, or
Chemraz®, refer to Appendix D: Model Code Explanation, page 67, for information) or all-
metal material. Full scale ranges are available from 10 Torr to 100 psi with a flow capacity of 50
sccm (standard cubic centimeters per minute) to 50 slm (standard liters per minute).
The 640 Series Pressure Controller can be used in either upstream or downstream pressure
control applications. The transducer inlet port is identified as the “Controlled Pressure Port” to
ensure that you install the 640 Pressure Controller into your system correctly.
The 640 Series Controllers provide two user-settable alarm trip points. The trip points can be set
from 1 to 100% of full scale. Each trip point controls an open collector transistor. An LED light
located on the top of the unit, indicates the trip point status.
Note
The proportional control valve in the 640 Pressure Controller is not a
positive shutoff valve. Depending upon your application, you may need
to install a separate positive shutoff valve.