MKS 651C - Chapter One: General Information; Introduction

Chapter One: General Information Introduction
17
Chapter One: General Information
Introduction
The Type 651C instrument is a self-tuning pressure controller for throttle valves. It can supply
±15 Volts to power and provide a readout for an attached capacitance manometer. The self-
tuning feature of the Type 651 unit determines system characteristics necessary for control. This
feature takes into account time constants, transfer functions of the valve and plumbing, valve
gain, pump speed, and many other important parameters when determining the system
characteristics. The 651 unit also includes an adjustable softstart function (to minimize
turbulence in the chamber and contamination of the process), Local/Remote transducer zeroing
capability, and two process limit relays to indicate if the pressure deviates from the desired trip
points.
Located on the front panel is a Key Lock switch used to select front panel or rear panel control.
The switch can lock the front panel controls as a safety measure to prevent accidental command
entries. The default window display on the front panel shows the pressure readout and the valve
position (% open). The pressure readout can be displayed in units of Torr, mTorr, mbar, µbar,
Pascal, kPa, cmH
2
O, or inH
2
O. Five reprogrammable set points are provided, each one having
the option of being setup for pressure or position control. Valve open, close, and stop functions
are also provided on the front panel for use in system setup and diagnostics.
The 651 instrument has a high-powered driver to operate most MKS type throttle valves,
including valves up to 100 mm (4”) with vacuum shut-off capability, giving the unit a control
range from 10
-4
to 760 Torr with the appropriate pressure transducers
Appendix C: Product
Compatibility
, page 117, lists all MKS products that are compatible with the 651 controller. All
MKS unheated and 45° C temperature-controlled, linear Baratron
®
transducers are compatible
with the 651 controller, which is equipped with a low-capacity power supply. The 651 unit can
be optionally equipped with a high-capacity power supply, enabling compatibility with 100° C
temperature-controlled, linear Baratron transducers. The 651 unit contains a battery-backed
memory module which stores configuration and
learned
system information while power is off.
There is also an optional valve failsafe battery backup available. The optional battery backup
allows user-configuration of the 651 instrument to drive a valve open or closed upon an AC
power failure.