MKS Baratron 127A User manual

110660-P1
Rev E, 6/97
Instruction Manual
MKS Baratron®
Type 127A and Type 128A
Absolute Pressure Transducers
Six Shattuck Road
Andover, MA 01810-2449
[phone] or [phone]
Fax: [phone]
E-mail: [e-mail]
Web site: http://www.mksinst.com

WARRANTY
Type 127A and 128A Equipment
MKS Instruments, Inc. (MKS) warrants that the equipment described above (the “equipment”) manufactured by
MKS shall be free from defects in materials and workmanship for a period of one year from date of shipment and
will for a period of two years from the date of shipment, correctly perform all date-related operations, including
without limitation accepting data entry, sequencing, sorting, comparing, and reporting, regardless of the date the
operation is performed or the date involved in the operation, provided that, if the equipment exchanges data or is
otherwise used with equipment, software, or other products of others, such products of others themselves correctly
perform all date-related operations and store and transmit dates and date-related data in a format compatible with
MKS equipment. THIS WARRANTY IS MKS’SOLE WARRANTY CONCERNING DATE-RELATED
OPERATIONS.
For the period commencing with the date of shipment of this equipment and ending one year later in the case of
defects in materials and workmanship, but two years later in the case of failure to comply with the date-related
operations warranty, MKS will, at its option, either repair or replace any part which is defective in materials or
workmanship or with respect to the date-related operations warranty without charge to the purchaser. The
foregoing shall constitute the exclusive and sole remedy of the purchaser for any breach by MKS of this warranty.
The purchaser, before returning any equipment covered by this warranty, which is asserted to be defective by the
purchaser, shall make specific written arrangements with respect to the responsibility for shipping the equipment
and handling any other incidental charges with the MKS sales representative or distributor from which the
equipment was purchased or, in the case of a direct purchase from MKS, with the MKS home office in Andover,
Massachusetts, USA.
This warranty does not apply to any equipment which has not been installed and used in accordance with the
specifications recommended by MKS for the proper and normal use of the equipment. MKS shall not be liable
under any circumstances for indirect, special, consequential, or incidental damages in connection with, or arising
out of, the sale, performance, or use of the equipment covered by this warranty.
MKS recommends that all MKS pressure and flow products be calibrated periodically (typically every 6 to 12
months) to ensure accurate readings. When a product is returned to MKS for this periodic re-calibration it is
considered normal preventative maintenance not covered by any warranty.
THIS WARRANTY IS IN LIEU OF ALL OTHER RELEVANT WARRANTIES, EXPRESSED OR IMPLIED,
INCLUDING THE IMPLIED WARRANTY OF MERCHANTABILITY AND THE IMPLIED WARRANTY OF FITNESS
FOR A PARTICULAR PURPOSE, AND ANY WARRANTY AGAINST INFRINGEMENT OF ANY PATENT.
11-98 110660-P1
This warranty is void if the product is installed using single or double metal ferrule compression
type vacuum fittings, shown below. These fittings are commonly tightened incorrectly, causing
damage to the pressure sensor.
SPECIAL NOTICE
Single Ferrule Double Ferrule

110660-P1
Rev E, 6/97
MKS Baratron
Type 127A and Type 128A
Absolute Pressure Transducers

Copyright © 1997 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
Inconelis a registered trademark of Inco Alloys International, Inc., Huntington, WV
Cajon, VCR, and VCOare registered trademarks of Cajon Company, Macedonia, OH

Table of Contents
iii
Table of Contents
Pressure Transducer Safety Information.................................................................................. 1
Symbols Used in This Instruction Manual.................................................................. 1
Symbols Found on the Unit ....................................................................................... 2
Safety Procedures and Precautions............................................................................. 3
Chapter One: General Information......................................................................................... 5
Introduction............................................................................................................... 5
How This Manual is Organized.................................................................................. 6
Customer Support...................................................................................................... 7
Chapter Two: Installation......................................................................................................9
How To Unpack the Type 127/128 Unit..................................................................... 9
Unpacking Checklist ..................................................................................... 9
Interface Cables ......................................................................................................... 10
Generic Shielded Cable Description .............................................................. 11
Example 1: Preferred Method To Connect Cable.......................................... 12
Example 2: Alternate Method To Connect Cable.......................................... 12
Product Location and Requirements........................................................................... 13
Operating Environmental Requirements ........................................................ 13
Setup ......................................................................................................................... 13
Dimensions................................................................................................... 14
Electrical Information................................................................................................ 15
Connector...................................................................................................... 16
Chapter Three: Overview....................................................................................................... 17
Circuit Description..................................................................................................... 17
Labels........................................................................................................................ 18
Chapter Four: Operation........................................................................................................19
How To Zero the Type 127/128 Transducer............................................................... 19
Chapter Five: Maintenance.................................................................................................... 21
General Information................................................................................................... 21

Table of Contents
iv
Zero Check....................................................................................................21
How To Clean the Unit..................................................................................21
Appendix A: Product Specifications.......................................................................................23
Type 127 Performance Specifications.........................................................................23
Type 127 Physical Specifications ...............................................................................24
Type 128 Performance Specifications.........................................................................25
Type 128 Physical Specifications ...............................................................................26
Appendix B: Model Code Explanation...................................................................................27
Model Code ...............................................................................................................27
Index ......................................................................................................................................29

List of Fi
g
ures and Tables
v
List of Figures and Tables
Figures
Figure 1: Preferred Method To Connect an Overall Metal Braided Shielded Cable................ 12
Figure 2: Alternate Method To Connect an Overall Metal Braided Shielded Cable................ 12
Figure 3: Dimensions of a Low Range Type 127/128 Transducer.......................................... 14
Figure 4: Dimensions of a High Range Type 127/128 Transducer ......................................... 14
Figure 5: Top View of a Type 127/128 Transducer................................................................ 15
Figure 6: Block Diagram of the Circuitry .............................................................................. 17
Figure 7: Serial Number Label .............................................................................................. 18
Tables
Table 1: Definition of Symbols Found on the Unit .....................................................................2
Table 2: Pinout of the Interface Connector................................................................................16
Table 3: Maximum Pressure Reading for Zero Adjustment.......................................................19
Table 4: Lowest Suggested Pressure Reading ...........................................................................20
Table 5: Lowest Suggested Pressure for Control.......................................................................20

List of Figures and Tables
vi

Pressure Transducer Safety Information
1
Pressure Transducer Safety Information
Symbols Used in This Instruction Manual
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.

Pressure Transducer Safet
y
Information
2
Symbols Found on the Unit
The following table describes symbols that may be found on the unit.
Definition of Symbols Found on the Unit
|
On (Supply)
IEC 417, No.5007 Off (Supply)
IEC 417, No.5008 Earth (
g
round)
IEC 417, No.5017
Protective earth
(
g
round)
IEC 417, No.5019
Frame or chassis
IEC 417, No.5020 Equipotentiality IEC 417, No.5021 Direct current IEC 417, No.5031 Alternatin
g
current
IEC 417, No.5032
Both direct and
alternatin
g
current
IEC 417, No.5033-a Class ll equipment
IEC 417, No.5172-a
Three phase
alternatin
g
current
IEC 617-2 No.020206
Caution, refer to
accompanyin
g
documents
ISO 3864, No.B.3.1
Caution, risk of
electric shock
ISO 3864, No.B.3.6 Caution, hot surface
IEC 417, No.5041
Table 1: Definition of Symbols Found on the Unit

Pressure Transducer Safety Information
3
Safety Procedures and Precautions
The following general safety precautions must be observed during all phases of operation of this
instrument. Failure to comply with these precautions or with specific warnings elsewhere in
this manual violates safety standards of intended use of the instrument and may impair the
protection provided by the equipment. MKS Instruments, Inc. assumes no liability for the
customer’s failure to comply with these requirements.
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 the materials in this product, including any 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.

Pressure Transducer Safet
y
Information
4
CHECK FOR LEAK-TIGHT FITTINGS
Before proceeding to instrument setup, carefully check all plumbing connections to the
instrument to ensure leak-tight installation.
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.

Chapter One: General Information Introduction
5
Chapter One: General Information
Introduction
The MKS Type 127A heated BaratronAbsolute Pressure Transducer and the Type 128A High
Temperature Absolute Pressure Transducer are capacitance manometers designed to provide
accurate, reliable, and repeatable pressure measurements in the range from 1000 Torr (1000
mmHg) to less than 0.1 Torr or micron (10-5 mmHg). These transducers utilize the latest
balanced bridge signal conditioning technology to provide accuracy and stability previously
unavailable in low cost capacitance manometers.
The Type 127 and Type 128 transducers are specifically designed to meet the needs of vacuum
process systems, where environmental and process conditions are particularly demanding. Both
units expose only Inconelto the process, which permits use with corrosive or dirty gases, and
eliminates contamination of the process with gauge materials. Measurements are independent of
gas composition; the 127 and 128 transducers measure true total pressure, regardless of the gas
species or whether it is a pure gas or a gas mixture. Temperature control of the sensor minimizes
the effects of ambient or process temperature variations typically encountered in process line
environments. The 127 transducer has the sensor temperature controlled at 45°C; the 128
transducer has the sensor temperature controlled at 100°C.
RFI shielding is standard to prevent interference from RF or noisy electrical environments. Both
units comply with the European EMC Directive 89/336/EEC which governs electromagnetic
compatibility. The units are protected against damage due to overpressure such as when the unit
is venting to atmosphere between process cycles. The overpressure limit is 35 psia, maximum,
for all ranges except 0.1 Torr range which is 20 psia, maximum. (However, MKS recommends
that you install an isolation valve to achieve the best zero stability.)
Both the 127 and 128 transducers are compatible with the Type PDR-C power supply/readout
units and closed-loop pressure/flow control systems such as the MKS Type 250 Pressure/Flow
Ratio Controller or the Type 152/252 Exhaust Valve Controller. In addition, the 127 and 128
transducers work with many commercial ±15 VDC power supplies, and standard digital volt
meters (DVMs).
The 127 and 128 transducers utilize the same construction and operation procedures and are
discussed interchangeably in this manual. The 127 unit is controlled at 45°C and has a black
case. The 128 unit is controlled at 100°C and has a gray case.

How This Manual is Organized Cha
p
ter One: General Information
6
How This Manual is Organized
This manual is designed to provide instructions on how to set up, install, and operate a Type
127/128 unit.
Before installing your Type 127/128 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 use the instrument and explains all the functions and
features.
Chapter Five, Maintenance, lists any maintenance required to keep the instrument in good
working condition.
Chapter Six, Troubleshooting, provides a checklist for reference should the instrument
malfunction.
Appendix A, Product Specifications, lists the specifications of the instrument.
Appendix B, Model Code Explanation, describes the model code.

Chapter One: General Information Customer Su
pp
ort
7
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
127/128 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.

Customer Support Cha
p
ter One: General Information
8
This page intentionally left blank.

Chapter Two: Installation How To Un
p
ack the T
yp
e 127/128 Unit
9
Chapter Two: Installation
How To Unpack the Type 127/128 Unit
MKS has carefully packed the Type 127/128 unit so that it will reach you in perfect operating
order. Upon receiving the unit, however, you should check for defects, cracks, broken
connectors, etc., to be certain that damage has not occurred during shipment.
Note Do not discard any packing materials until you have completed your
inspection and are sure the unit arrived safely.
If you find any damage, notify your carrier and MKS immediately. If it is necessary to return the
unit to MKS, obtain an ERA Number (Equipment Return Authorization Number) from the MKS
Service Center before shipping. Please refer to the inside of the back cover of this manual for a
list of MKS Calibration and Service Centers.
Unpacking Checklist
Standard Equipment:
•Type 127 or Type 128 Unit
•Type 127/128 Instruction Manual (this book)
Optional Equipment:
•Electrical Connector Accessories Kit - 127A-K1 or 128A-K1 (which includes a mating
connector for the 15-pin Type “D” Interface connector)
•Interface cables
•PDR-C-1C/2C Power Supply/Readout
•RM-6 Rack Mount Kit
•Pressure/Flow Controller

Interface Cables Cha
p
ter Two: Installation
10
Interface Cables
As of January 1, 1996, most products shipped to the European Community must comply with the
EMC Directive 89/336/EEC, which covers radio frequency emissions and immunity tests. In
addition, as of January 1, 1997, some products shipped to the European Community must also
comply with the Product Safety Directive 92/59/EEC and Low Voltage Directive 73/23/EEC,
which cover general safety practices for design and workmanship. MKS products that meet
these requirements are identified by application of the CE Mark.
To ensure compliance with EMC Directive 89/336/EEC, an overall metal braided shielded cable,
properly grounded at both ends, is required during use. No additional installation requirements
are necessary to ensure compliance with Directives 92/59/EEC and 73/23/EEC.
MKS offers a full line of cables for all MKS equipment.
Note 1. An overall metal braided shielded cable, properly grounded at both
ends, is required during use to meet CE specifications.
2. To order a metal braided shielded cable, add an “S”after the cable
type designation. For example, to order a cable to connect a 127 unit
to a PDR-C unit, order CB127S-1 for an overall metal braided
shielded cable; order CB127-1 for a non-shielded cable.
Interface Cables
To Connect To A . . . Use Cable . . .
PDR-C-1C/2C, PDR-5B CB127S-1-XX; CB127-1-XX
244, 250, 252, 152 260 Series CB258S-1-XX; CB258-1-XX
146, 186, 651, 652, 660 CB259S-5-XX; CB259-5-XX
where XX indicates the cable length

Chapter Two: Installation Interface Cables
11
Generic Shielded Cable Description
Should you choose to manufacture your own cables, follow the guidelines listed below:
1. The cable must have an overall metal braided shield, covering all wires. Neither aluminum
foil nor spiral shielding will be as effective; using either may nullify regulatory compliance.
2. The connectors must have a metal case which has direct contact to the cable’s shield on the
whole circumference of the cable. The inductance of a flying lead or wire from the shield to
the connector will seriously degrade the shield’s effectiveness. The shield should be
grounded to the connector before its internal wires exit.
3. With very few exceptions, the connector(s) must make good contact to the device’s case
(ground). “Good contact”is about 0.01 ohms; and the ground should surround all wires.
Contact to ground at just one point may not suffice.
4. For shielded cables with flying leads at one or both ends; it is important at each such end, to
ground the shield before the wires exit. Make this ground with absolute minimum length.
Refer to Figures 1 and 2, page 12. (A ¼inch piece of #22 wire may be undesirably long
since it has approximately 5 nH of inductance, equivalent to 31 ohms at 1000 MHz). After
picking up the braid’s ground, keep wires and braid flat against the case. With very few
exceptions, grounded metal covers are not required over terminal strips. If one is required, it
will be stated in the Declaration of Conformity or in the instruction manual.
5. In selecting the appropriate type and wire size for cables, consider:
A.The voltage ratings;
B.The cumulative I2R heating of all the conductors (keep them safely cool);
C.The IR drop of the conductors, so that adequate power or signal voltage gets to the device;
D.The capacitance and inductance of cables which are handling fast signals, (such as data
lines or stepper motor drive cables); and
E.That some cables may need internal shielding from specific wires to others; please see the
instruction manual for details regarding this matter.

Interface Cables Cha
p
ter Two: Installation
12
Example 1: Preferred Method To Connect Cable
(shown on a transducer)
Transducer
Overall Insulation
(if present)
Bare Metal Cable Clamp
Makin
g
Firm Contact To Braid
Braid Here Is Desirable
(but not usually necessary)
Keep Wires and Braid
Flat A
g
ainst Case
Metal Cable Clamp
Screw
Split Lock Washer
External Tooth Lock Washer
Transducer Housin
g
Optional Plastic or Metal Cable
Clamp (For Physical Strain Relief)
Figure 1: Preferred Method To Connect an Overall Metal Braided Shielded Cable
Example 2: Alternate Method To Connect Cable
(shown on a transducer)
Transducer
Overall Insulation
(
if present
)
Braid Strands Twisted
Under Washer
Keep Wires Flat
A
g
ainst Case
Optional Plastic or Metal Cable
Clamp
(
For Ph
y
sical Strain Relief
)
Screw
Split Lock Washer
Flat Washers
External Tooth Lock Washer
Transducer Housin
g
Figure 2: Alternate Method To Connect an Overall Metal Braided Shielded Cable
Use this method when cable clamp is not available