MKS 649B - How To Adjust the Trip Point Values

Chapter One: General Information Introduction
5
Chapter One: General Information
Introduction
The MKS Type 649B is the RoHS-compliant version of the industry standard Type 649
instrument that provides both pressure control and flow metering in one compact unit. The 649
pressure controller includes a Baratron
®
capacitance manometer, proportioning control valve,
closed-loop electronics, and patented thermal mass flow sensor. The closed-loop control circuitry
enables the unit to function as a proportional-integral (PI) controller. The combination of a
pressure controller and mass flow meter in one unit makes the 649 pressure controller the ideal
solution for backside wafer cooling applications. In addition, the unit’s compact size and small
footprint reduce space requirements compared to multi-component systems.
The 649 pressure controller is available with full scale pressure ranges from 10 Torr [1333 Pa] to
100 Torr [13.3 kPa] and full scale flow rates from 10 to 5000 sccm (nitrogen equivalent). The
649 unit is metal sealed; the valve plug material can be metal, Viton
®
, Kel-F
®
, or Kalrez
®
. The
unit can have either Cajon
®
4-VCR
®
male (or equivalent) or 8-VCR male (or equivalent) male
fittings.
One Type “D” connector, located on the top of the unit, accepts the input power and has both the
pressure (input and output) and flow (output) signals. You can connect the 649 controller to an
MKS Type 247 or 246 Mass Flow Controller Power Supply/Readout or a Type 647 Mass Flow
and Pressure Programmer/Display unit.
The 649 pressure controller provides two user-settable alarm trip points. The pressure 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.
Caution
The control valve within the 649 unit is not a positive shutoff valve.
You may need to install a separate positive shutoff valve in your
system.
Design Features of the Integral Mass Flow Meter
The design of the integral mass flow meter incorporates an advanced flow sensor (U.S. Patent
1
;
Foreign Patents Pending) and an optimized bypass. The latest generation two-element sensing
circuit provides accurate, repeatable performance even in low flow ranges (< 10 sccm). Low
temperature effect from ambient temperature change and a low attitude sensitivity effect are also
ensured. The newly optimized sensor/bypass arrangement minimizes the flow splitting error for
1
U.S. Patent 5461913; foreign patents pending.