MKS Baratron 122A Series User manual

110448-P1
Rev E, 6/96
MKS Baratron®
Type 122A
Absolute Pressure Gauge
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Copyright©1996 by MKS Instruments, Inc.
All rights reserved. No part of this work may be reproduced or transmitted in any form or by any
means, electronic or mechanical, including photocopying and recording, or by any information
storage or retrieval system, except as may be expressly permitted in writing by MKS Instruments,
Inc.
Baratron®is a registered trademark of MKS Instruments, Inc., Andover, MA
Cajon®, VCR®, VCO®, and Ultra-Torr®are registered trademarks of Cajon Company,
Macedonia, OH
Inconel®is a registered trademark of Inco Alloys International, Inc., Huntington, WV

Table of Contents
iii
Table of Contents
Safety Procedures and Precautions.......................................................................................... 1
Chapter One: General Information......................................................................................... 3
Introduction............................................................................................................... 3
How This Manual is Organized.................................................................................. 4
Customer Support...................................................................................................... 4
Chapter Two: Installation ......................................................................................................5
How To Unpack the Type 122 Unit............................................................................ 5
Unpacking Checklist ..................................................................................... 5
Dimensions................................................................................................................ 6
Setup ......................................................................................................................... 7
Mounting Instructions ................................................................................... 7
Electrical Installation..................................................................................... 7
Cables........................................................................................................... 8
Chapter Three: Overview....................................................................................................... 11
Sensor........................................................................................................................ 11
Signal Conditioner Electronics................................................................................... 13
Chapter Four: Operation........................................................................................................15
How To Adjust the Zero ............................................................................................ 15
Lowest Recommended Pressure Reading....................................................... 16
Lowest Recommended Pressure Control........................................................ 16
Highest Base Pressure for Proper Zero Adjust ............................................... 16
Chapter Five: Maintenance.................................................................................................... 17
General Information................................................................................................... 17
Signal Conditioner Electronics................................................................................... 17
Sensor........................................................................................................................ 17

Table of Contents
iv
Appendix A: Product Specifications.......................................................................................19
Appendix B: Product Code.....................................................................................................21
Index ......................................................................................................................................23

List of Fi
g
ures
List of Tables
v
List of Figures
Figure 1: Dimensions of a 122 Transducer............................................................................. 6
Figure 2: Electrical Connections............................................................................................ 7
Figure 3: Interface Cables for the 122 Transducer.................................................................. 9
Figure 4: Type 122 Transducer.............................................................................................. 11
Figure 5: Cross Sectional View of a 122 Transducer.............................................................. 12
Figure 6: Block Diagram of the 122 Transducer..................................................................... 13
List of Tables
Table 1: Cable Color Codes........................................................................................................8
Table 2: Suggested Pressures for Zero Adjustment....................................................................16

List of Figures
List of Tables
vi

Safety Procedures and Precautions
1
Safety Procedures and Precautions
DO NOT SUBSTITUTE PARTS OR MODIFY INSTRUMENT
Do not install substitute parts or perform any unauthorized modification to the instrument.
Return the instrument to an MKS Calibration and Service Center for service and repair to ensure
that all safety features are maintained.
SERVICE BY QUALIFIED PERSONNEL ONLY
Operating personnel must not remove instrument covers. Component replacement and internal
adjustments must be made by qualified service personnel only.
USE CAUTION WHEN OPERATING WITH HAZARDOUS MATERIALS
If hazardous materials are used, users must take responsibility to observe the proper safety
precautions, completely purge the instrument when necessary, and ensure that the material used is
compatible with sealing materials.
PURGE THE INSTRUMENT
After installing the unit, or before its removal from a system, be sure to purge the unit completely
with a clean dry gas to eliminate all traces of the previously used flow material.
USE PROPER PROCEDURES WHEN PURGING
This instrument must be purged under a ventilation hood, and gloves must be worn to protect
personnel.
DO NOT OPERATE IN EXPLOSIVE ATMOSPHERES
To avoid explosion, do not operate this product in an explosive atmosphere unless it has been
specifically certified for such operation.
USE PROPER FITTINGS AND TIGHTENING PROCEDURES
All instrument fittings must be consistent with instrument specifications, and compatible with the
intended use of the instrument. Assemble and tighten fittings according to manufacturer's
directions.
CHECK FOR LEAK-TIGHT FITTINGS
Before proceeding to instrument setup, carefully check all plumbing connections to the
instrument to ensure leak-tight installation.

Safet
y
Procedures and Precautions
2
OPERATE AT SAFE INLET PRESSURES
This unit should never be operated at pressures higher than the rated maximum pressure (refer to
the product specifications for the maximum allowable pressure).
INSTALL A SUITABLE BURST DISC
When operating from a pressurized gas source, a suitable burst disc should be installed in the
vacuum system to prevent system explosion should the system pressure rise.
KEEP THE UNIT FREE OF CONTAMINANTS
Do not allow contaminants of any kind to enter the unit before or during use. Contamination
such as dust, dirt, lint, glass chips, and metal chips may permanently damage the unit.
Definitions of WARNING, CAUTION, and NOTE messages used throughout the manual.
Warning The WARNING sign denotes a hazard. It calls attention to a
procedure, practice, condition, or the like, which, if not
correctly performed or adhered to, could result in injury to
personnel.
Caution The CAUTION sign denotes a hazard. It calls attention to an
operating procedure, practice, or the like, which, if not correctly
performed or adhered to, could result in damage to or destruction of
all or part of the product.
Note The NOTE sign denotes important information. It calls attention to a
procedure, practice, condition, or the like, which is essential to highlight.

Chapter One: General Information Introduction
3
Chapter One: General Information
Introduction
The MKS Baratron®Type 122A Absolute Pressure Transducer marks the beginning of a new era
in low cost pressure measurement. Using a latest-generation single-sided dual-electrode Inconel®
sensor coupled with a new fixed-frequency bridge signal conditioner, the 122 provides operation
which is inherently temperature stable at zero pressure, capable of withstanding high overpressure
conditions with minimal or no shifts in output over its range, and high resistance to corrosive
environments.
The variable-capacitance sensor is the result of over 25 years of research, development and
customer experience in total pressure measurement. The design incorporates a tensioned metal
diaphragm (Inconel), one side of which is exposed to the gas whose pressure is to be measured.
The other (reference) side of the diaphragm contains a dual electrode assembly (previously found
in premium transducers only) sealed in a high vacuum reference cavity which is maintained by a
chemical getter system.
The signal conditioning electronics board contains a fixed-frequency oscillator, balance-sensing
circuit, linearization circuitry and amplifiers which provide a 0 to 10 Volt DC full scale output.
The signal conditioner is inherently temperature stable at balance (pressure = 0 Torr) and is self-
compensating with temperature changes at other pressures.
A drawn aluminum can forms the protective cover for the transducer and a PC board mounted
removable terminal block allows connections to be easily made for ± 15 VDC power inputs and
the 0 to 10 VDC pressure signal output. In addition, the aluminum cover works in conjunction
with an inner PC shield board with RF bypass capacitors to virtually eliminate RFI and EMI.
Refer to Figure 5, page 12, for a cross sectional view of the 122 transducer.

How This Manual is Organized Cha
p
ter One: General Information
4
How This Manual is Organized
This manual is designed to provide instructions on how to set up, install, and operate a Type 122
unit.
Before installing your Type 122 unit in a system and/or operating it, carefully read and
familiarize yourself with all precautionary notes in the Safety Messages and Procedures
section at the front of this manual. In addition, observe and obey all WARNING and
CAUTION notes provided throughout the manual.
Chapter One: General Information, (this chapter) introduces the product and describes the
organization of the manual.
Chapter Two: Installation, explains the environmental requirements and describes how to mount
the instrument in your system.
Chapter Three: Overview, gives a brief description of the instrument and its functionality.
Chapter Four: Operation, describes how to operate the instrument.
Chapter Five: Maintenance, describes repair and return policies for the 122 transducer.
Appendix A: Product Specifications, lists the specifications of the instrument.
Appendix B: Product Code, describes the instrument’s product code.
Customer Support
Standard maintenance and repair services are available at all of our regional MKS Calibration and
Service Centers, listed on the back cover. In addition, MKS accepts the instruments of other
manufacturers for recalibration using the Primary and Transfer Standard calibration equipment
located at all of our regional service centers. Should any difficulties arise in the use of your Type
122 instrument, or to obtain information about companion products MKS offers, contact any
authorized MKS Calibration and Service Center. If it is necessary to return the instrument to
MKS, please obtain an ERA Number (Equipment Return Authorization Number) from the MKS
Calibration and Service Center before shipping. The ERA Number expedites handling and
ensures proper servicing of your instrument.
Please refer to the inside of the back cover of this manual for a list of MKS Calibration and
Service Centers.
Warning All returns to MKS Instruments must be free of harmful,
corrosive, radioactive, or toxic materials.