MKS HPS 945 Series User manual

HPS®Products Series 945
DigitalPirani
Vacuum Sensor System
OPERATION AND
MAINTENANCE MANUAL

Digital Pirani Vacuum Sensor System
HPS®Products Series 945
DigitalPirani
Vacuum Sensor System
July 1999
Part #109450020 Rev. A1

Digital Pirani Vacuum Sensor System
Part#945-X-XXX-XX
–__– ____ __–____
Serial # __ __ __ __ __ __
Please fill in these numbers and have
themreadilyavailablewhencallingfor
serviceoradditionalinformation.
(The part number can be found on your
packing slip, and the serial number is
located on the back panel of the
controller.)
© 1999 by MKS Instruments, Inc. HPS®Products, Inc., All rights reserved.
IsaregisteredtrademarkofMKSInstruments,Inc.,HPSTM Products,Inc.
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VCRisaregisteredtrademarkofCajonCo.
Formore information or literature, contact:
MKS Instruments, Inc., HPS®Products, Inc.
5330SterlingDrive
Boulder,CO80301USA
Phone: [phone]
800-345-1967
FAX: [phone]

Digital Pirani Vacuum Sensor System
Table of contents
Table of contents
Package Contents ..................................................................... 1
Symbols Used in this Manual.................................................... 2
Safety Precautions .................................................................... 3
Specifications............................................................................ 5
Controller................................................................................................. 5
SensorTube ...................................................................................... 6
Feature and Control Locations .................................................. 7
Typical Applications for the Series 945 Pirani System .............. 8
About the SensaVac® Series 945 Pirani Vacuum
Sensor System .......................................................................... 9
Installing the Series 945 Pirani System................................... 10
Pirani Sensor Installation .......................................................................10
Location ...........................................................................................10
Orientation .......................................................................................10
Contamination..................................................................................10
Vacuum Connection .........................................................................10
PiraniController Installation....................................................................11
ControllerMounting ..........................................................................11
Connectingthe Sensorto theController...........................................12
AC PowerCord ................................................................................12
FuseReplacement...........................................................................13
AccessoryConnector.......................................................................13
Relay Inductive Loads and Arc Suppression ...................................14
Operating the Series 945 Pirani System.................................. 15
Reading Pressure ...................................................................................15
SensorAdjustment.................................................................................16
Calibratingfor Zero and Atmosphere ......................................................17
Adjusting the Set Point...........................................................................17
Venting to Atmosphere ...........................................................................17
BufferedAnalog Output ..........................................................................18
Usewith Computers ...............................................................................18
LeakDetection .......................................................................................18

Digital Pirani Vacuum Sensor System
Using the Series 945 Pirani System with Other Gases............ 20
Nitrogen Equivalent Pressure .................................................................20
Calibratingfor OtherGases ....................................................................21
Maintaining the Series 945 Pirani System............................... 22
Troubleshootingand Service...................................................................22
Cleaningthe Pirani Controller Front Panel ..............................................22
Cleaning the Pirani Sensor .....................................................................23
Testing the Pirani Sensor .......................................................................23
Accessories............................................................................. 24
ProductWarranty ..................................................................... 25
Notes....................................................................................... 26
Appendix A: How the Series 945 Pirani System Works..........A.1
Theory of aThermal Conductivity Sensor............................................. A.1
Measurement Limits............................................................................. A.1
The Series 945 Pirani System Design Overview .................................. A.2
Amplifier ........................................................................................ A.2
Output............................................................................................ A.2
Set Point Relays ............................................................................A.2
Comparator .................................................................................... A.2
Notes......................................................................................A.3

1
Digital Pirani vacuum Sensor System
Before unpacking your Series 945 Digital Pirani Vacuum Sensor System, check
all surfaces of the packing material for shipping damage.
Please be sure that your Series 945 Pirani System package contains
these items:
1Series 945PiraniController
1 female, 9-pin, subminiature D (D-sub) Accessory connector
1powercord
1 Series 945 Digital Pirani Vacuum Sensor System User's Manual.
The Series 945 System's Pirani Sensor and its connecting cable are sold
separately.Please referto page 24 for necessary ordering information.
If any items are missing from the package, call HPS®Products
CustomerServiceat1-303-449-9861or1-800-345-1967.
Inspect the Series 945 Pirani System for visible evidence of damage. If it has
been damaged in shipping, notify the carrier immediately. Keep all shipping
materials and packaging for claim verification. Do not return the product to
HPS®Products.
Package Contents

2Digital Pirani vacuum Sensor System
The first two symbols below, located on your Series 945 Controller and/or
Sensor, identify critical safety concerns. They are used throughout this
manual to further define the safety concerns associated with the product.
The last two symbols identify other information in this manual that is
essential to highlight or useful in achieving optimal performance from your
Series 945 Pirani System.
CAUTION: Risk of electrical shock.
CAUTION: Refertomanual.
Failure to heed message could result in personal injury
or serious damage to the equipment or both.
Failure to heed message could result in damage to the
equipment.
Informationcallingattentiontoimportantprocedures,
practices, or conditions.
Symbols Used in this Manual

3
Digital Pirani vacuum Sensor System
Safety Precautions
Do not use the Series 945 Pirani System's Sensor with
explosive gas mixtures or gases that are combustible in air.
If the control circuit fails or an exothermic catalytic reaction occurs at the
sensor wire, the wire could ignite the gas mixture.
When using the Series 945 Pirani System with gases other
thanair or nitrogen, avoid overpressure to prevent any
possibility of explosion.
Since the Sensor is calibrated for air/nitrogen, the measured pressure of
another gas will differ from its true pressure. Calibrations diverge widely at
higher pressures. Since the different gases are not linearly related, a gas
correctionfactorcouldleadtohazardousoverpressure.Capacitance
manometersand mechanical dial gauges are best suitedfor higherpressures.
Refer to page 20 for use with other gases.
In a system which is filled from a pressurized source, install a safety relief
valve or burst disc to safely limit pressure.
Turn off power to the Controller before connecting or
disconnecting a cable to the Sensor.
Connecting or disconnecting cables while the Controller is on may damage
the Sensor.
Properlyground the Controller.
The Controller is grounded through the conductor of the power cord. If the
protective ground connection is lost, all accessible conductive parts may
pose a risk of electrical shock. Plug the cord into a properly grounded
outlet only.
When applying a voltage or current to the ports on the rear of the panel, do
not exceed manufacturer's specifications. Electrical shock or Controller
damagemayresult.
Allow only qualified technicians to service the Series 945
Pirani System.
Users should not remove covers, casings, or plug-in components. Injury may
result. Any part replacement or internal adjustments must be performed by a
qualified technician only.

4Digital Pirani vacuum Sensor System
TheSeries 945 Pirani Controller contains lethal voltages
within the casing.
Avoid danger of electrical shock. Unplug the power cord before
opening the casing.
To prevent damage to the Series 945 Pirani Controller,
use the correct line voltage.
Use the Controller with the specified line voltage only. Use a fuse of the
correct type, voltage, and current rating. Only qualified personnel should
change line voltage or fuse ratings if required.
Outside of the U.S., use only a detachable cord set that has conductors with
a cross-sectional area equal to or greater than 0.75 mm2. Power cables
should have agency approval, for example, VDE, Semko, or SEV.
The Series 945 Pirani System and all its accessories must be used as
instructed by MKS Instruments, Inc., HPS®Products Inc., to ensure safe
operation. Use or modification of the equipment in a manner not
consistentwithspecificationsmayrendertheproduct'sinherent
protectionuseless.