MKS HPS 903 Series User manual

Inverted MagnetronTransducer
(IMT)
ColdCathodeIonization
VacuumSensor
OPERATION AND
MAINTENANCE MANUAL
HPSTM Products Series 903

Please Note:
MKS Instruments provides these documents as the latest version for the revision indicated.
The material is subject to change without notice, and should be verified if used in a critical
application.

Cold Cathode Ionization Vacuum Sensor
HPSTM Products Series 903
Inverted MagnetronTransducer
(IMT)
ColdCathodeIonization
VacuumSensor
JUNE 1999
PART #1090300 REV. A

Cold Cathode Ionization Vacuum Sensor
Part#1090300XX
__ __
Serial # __ __ __ __ __ __
Please fill in these numbers and
havethemreadilyavailablewhencalling
forserviceoradditionalinformation.
(The part number can be found on
your packing slip, and both the part
numberandserialnumberarelocatedon
the bottom side of the housing.)
© 1999 MKS Instruments, Inc. HPSTM Products, Inc., All rights reserved.
ALCONOXisaregisteredtrademarkofAlconox,Inc.
IgniTorrisatrademarkofMKSInstruments,Inc.,HPSTM Products,Inc.
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IsaregisteredtrademarkofMKSInstruments,Inc.,HPSTM Products,Inc.
For more information or literature, contact:
MKS Instruments, Inc., HPSTM Products, Inc.
5330 Sterling Drive
Boulder, CO 80301 USA
Phone: [phone]
800-345-1967
FAX: [phone]

Cold Cathode Ionization Vacuum Sensor
Table of Contents
Table of Contents
Package Contents ..................................................................... 1
Symbols Used in this Manual.................................................... 1
Safety Precautions .................................................................... 2
Specifications............................................................................ 3
Feature and Control Locations .................................................. 5
Typical Applications for the Series 903 (IMT) ............................ 6
About the HPSTM Products Series 903 (IMT) ............................. 7
Installing the Series 903 (IMT)................................................... 8
Location .................................................................................................... 8
Orientation ................................................................................................ 8
Contamination........................................................................................... 8
VacuumConnection .................................................................................. 9
ElectricalConnection ................................................................................ 9
Input/OutputWiring ................................................................................... 9
RelayInductive LoadsandArc Suppression ........................................... 11
Operating the Series 903 (IMT) ............................................... 12
Starting the (IMT) ................................................................................... 12
ReadingPressure ................................................................................... 12
Equation for ConvertingVoltage to Pressure ........................................... 13
Using the Set Point ................................................................................. 13
Ventingto Atmosphere............................................................................ 14
Analog-to-Digital(A/D)Converter ............................................................ 14
PreparingforBakeout ............................................................................. 14
LeakDetection........................................................................................ 14
Using the Series 903 (IMT) with Other Gases ......................... 16
CalibratingforOther Gases..................................................................... 17
Maintaining the Series 903 (IMT) ............................................ 18
Troubleshootingand Service ................................................................... 18
Contaminationof the (IMT)Sensor ......................................................... 19
Disassembly .................................................................................................................. 19
Cleaning.......................................................................................................................... 19
Assembly........................................................................................................................ 20

Cold Cathode Ionization Vacuum Sensor
Accessories/Part Replacement ............................................... 22
ProductWarranty ..................................................................... 23
Notes....................................................................................... 24
Appendix A:How the Series 903 (IMT) Works........................ A.1
Theoryof a ColdCathode Ionization Sensor ..........................................A.1
Notes......................................................................................A.3

1
Cold Cathode Ionization Vacuum Sensor
BeforeunpackingyourSeries903InvertedMagnetronTransducer(IMT)
Vacuum Sensor, check all surfaces of the packing material for shipping
damage.
Please be sure that your Series 903 (IMT) package contains these items:
1(IMT)unit (integrated sensortube and electronics)
1female,9-pinsubminiatureD(D-sub)connector
1 Series903InvertedMagnetronTransducer(IMT)Cold
CathodeIonizationVacuumSensor User'sManual.
If any items are missing from the package, call HPSTM Products
CustomerServiceat1-303-449-9861or1-800-345-1967.
Inspect the (IMT) 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 HPSTM.
Package Contents
t
t
t
Symbols Used in this Manual
The first two symbols below, that may be located on your Series 903 (IMT),
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 or useful in achieving optimal performance from the (IMT).
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.
Calls attention to important procedures, practices, or
conditions.
(

2Cold Cathode Ionization Vacuum Sensor
Install the (IMT) only on a grounded vacuum system.
When using an (IMT) with a flange and an elastomer seal, use an all-metal
clamp to ensure electrical continuity between the( IMT) and the grounded
vacuum system.
When using an ( IMT) with a 1-inch tube, use a ground strap to connect the
sensor to the grounded vacuum system.
Do not connect power to the (IMT) unless its flange is attached to
thevacuum system andtheelectronics assembly isfastened to
thesensorhousing.
Do not exceed voltage requirements as this may damage the electronics
assembly. Refer to the information on page 9 for proper connection
instructions.
The (IMT) may be connected only to devices conforming to
therequirements ofasecondary extralowvoltage inaccordance
withEN61010-1.
Allow only qualified technicians to service the (IMT).
Users should not remove covers, casings, or plug-in components. Injury may
result. Turn off power to the (IMT) before proceeding with maintenance. Only
aqualified technician should replace oradjust electronic components.
As much as 4 kV may be present in the (IMT) during operation. The current is
limited to 100 mA.
The Series 903 (IMT) must be used as instructed by MKS Instruments,
Inc., HPSTM Products Inc., for safe operation. Using or modifying the
equipmentinconsistentwithspecificationsmayrendertheproduct's
inherentprotectionuseless.
Safety Precautions

3
Cold Cathode Ionization Vacuum Sensor
Specifications
MeasuringRange 3.0 x 10-10 to 5.0 x 10-3 Torr
3.9 x 10-10 to 6.5 x 10-3 mbar
3.9 x 10-8 to 6.5 x 10-1 Pa
Set Point Range 1.0 x 10-9 to 1.0 x 10-3 Torr
1.3 x 10-9 to 1.3 x 10-3 mbar
1.3 x 10-7 to 1.3 x 10-1 Pa
Repeatability Approximately±5%
CalibrationGas Air/nitrogen
OperatingTemperatureRange 0°to50°C(32° to 122°F)
BakeoutTemperature 400°C(752°F)maximumforCF
flangedunit; without electronics,
cable,or magnet
RelativeHumidity 80%maximumfor temperatures
lessthan31°C,decreasinglinearly
to 50% maximum at 40°C
Altitude 2000m (6561 ft) maximum
Insulation PollutionDegree2
Controls 1 relay set point
RelayContactRating SPDT, 1 A @ 30 VDC, resistive
RelayHysteresis 150mV*
RelayResponse < 50 msec (0 to 99%)
for DP from 5.0 x 10-8 Torr to
3.0 x 10-4 Torr
PowerRequirement 14 to 30 VDC, 150 mA maximum
Output Voltage 1.5 to 8.7 VDC, linear output,
30Wmaximum outputimpedance
OutputLoad 100kWnominal
10kWminimum
*150 mV is equivalent to a change in pressure of 1.41 (or 100.150) times the set
point, e.g., if the relay is set to activate at 2.0 x 10-6 Torr (5.301 V), it will
deactivate at 2.82 x 10-6 Torr (5.451 V).

4Cold Cathode Ionization Vacuum Sensor
Design and/or specifications subject to change without notice.
InternalOperatingVoltage 4 kV maximum
current limited to 133 mA
InstallationOrientation Any
Internal Volume 0.9 in.3(15.0 cm3) maximum
MaterialsExposed to Vacuum SS 304, SS 302, aluminum, glass,
Inconel®X-750,aluminaceramic
Display LED indicators for set point (red),
highvoltage(yellow),andpower
(green)
ElectronicCasing ABS plastic, UL 94-5V flame rating
(withconductivecoating)
CasingDimensions 5" x 3" x 4.2"
(W x D x H) (127 mm x 76 mm x 108 mm)
TypicalWeight(with CF Flange) 2.3 lb (1.04 kg)
VacuumConnection KF 25
KF 40
2¾"CF(rotatable)
1" tubing
CECertification EMC Directive
GeneralProductSafety Directive

5
Cold Cathode Ionization Vacuum Sensor
Feature and Control Locations
Side View
Front View
LEDPowerOn-OffIndicator(Green)
LEDHighVoltageIndicator(Yellow)
LED Set Point Indicator (Red)
Phillips Head Screws (Access to Sensor Tube)
Set Point Adjustment Potentiometer
Tip Jack for Set Point Monitor
Tip Jack for Common
Male,9-pinD-subConnector
SensorTube Vacuum Port
Top View
l
4l
1l 2l 3
l
5
l
6
l
7
l
8
l
9
l
3
l
9
l
8
l
6
l
5
l
4
l
2
l
1
l
7

6Cold Cathode Ionization Vacuum Sensor
Measurementofhighvacuum chamberpressures
Control of high vacuum systems and process
sequencing using the relay set point
Sensingabnormalpressure andtaking appropriatesecurity
measures using the relay set point
Controlling system pressure usingtheanalog output as
input to an automatic pressure controller
Starting or stopping system processes with the relay set point
Measuringpressures ofbackfilled gases
Leak testing your vacuum system
Typical Applications for the
Series 903 (IMT)
t t
t t
t t
t t
t t
t t
t t

7
Cold Cathode Ionization Vacuum Sensor
About the HPSTM Products
Series 903 (IMT)
TheSeries903InvertedMagnetronTransducer(IMT)is a compact cold cathode
vacuumsensor with anintegrated electronic control circuit.
The (IMT’s) simple modular design, high reliability,
and low cost make it especially attractive
to OEM equipment manufacturers. Its
sensor tube is available with one of four
standard vacuum interfaces.
The (IMT) is designed for applications
whichrequirepressure
measurementin the
range from 5 x 10-3
down to 3 x 10-10 Torr.
Its rapid response and
widemeasurementrange
providetheequipment
designerwithmaximum
flexibility. Because it can
operateautonomouslyor
as part of a control
system, it is adaptable to
several roles, including that
of a monitor or an alarm.
The (IMT) is normally off and
requires shorting its High
Voltage Enable pin to ground
to turn it on. This allows the
(IMT) to be controlled by a
higher pressure sensor such
as the HPSTM Products
SensaVac Series 907 Analog
ConvectionTransducer(ACT).
For process control, the (IMT)
has one adjustable relay set
point. An LED indicates the status
of the set point.
The (IMT) can be located out of sight — pressure is then read from a
standarddigital voltmeteror analog-to-digital converter and computer.

8Cold Cathode Ionization Vacuum Sensor
Installing the Series 903 (IMT)
Location
Locate the (IMT) where it can measure process chamber or manifold
pressure. Install it away from pumps, other vibration sources, and gas
sources to give the most representative values.
Orientation
The (IMT) can be installed with the body set in any
direction. Operating position does not affect accuracy.
Where space is limited, it may be difficult to position an
(IMT) with a CF flange. If the bolts cannot be fed through
the flange toward the electronics assembly, it will first be
necessary to remove the electronics assembly from the
sensor to install the (IMT).
Remove the two Phillips head screws on top of the (IMT)
and remove the electronics assembly. Note the alignment
of the feed through pins with the orientation of the
electronics assembly as shown to the right.
Before assembling the (IMT), inspect the pins to make sure
they have not been bent. Straighten them if necessary. The
sensor is keyed to the electronics assembly. Rotate the
electronics assembly onto the sensor until it is fully seated.
Install the two Phillips head screws.
Contamination
Locate and orient the (IMT) where contamination is least
likely. If it is installed directly above a diffusion pump, for
example, oil vapor could contaminate the cathode, anode, or other vacuum
exposed components, causing the calibration to shift.
Installing it with the vacuum port facing down is preferable as this helps
prevent contaminants falling into it.
Operationat pressures above 10-3 Torr for extendedperiodscan promote the
negative effects of contamination in the sensor.
Alignment of sensor with
electronics assembly
Feedthrough
pins
Key

9
Cold Cathode Ionization Vacuum Sensor
Vacuum Connection
Standard(IMT)vacuuminterfacesareshownabove.
Use an all-metal clamp to mount a KF 25 or KF 40 flanged sensor body.
Electrical Connection
Mount the (IMT) to a grounded vacuum system.
Use a cable with a mating, 9-pin D-sub connector with strain reliefs to ensure
proper electrical connection and to reduce stress on the connectors.
Connect the cable to the (IMT) and to your power supply or measuring device
beforeoperatingthe(IMT).
Ensurea low impedance electrical connectionbetween the
(IMT) and the grounded vacuum system to shield the sensor
fromexternalelectromagneticsources.
Input/Output Wiring
The chart and accompanying figure on the next page identify the pins of the
IMT connector and their functions. Make a cable using this information.
To be in compliance with EN 50082-1 immunity requirements, use a braided,
shielded cable. Connect the braid to the metal hoods at both ends of the
cable with the end for power supply connected to earth ground. The connector
kit shipped with the (IMT) includes a metal shell which provides an easy and
effective means of connecting the braid to it.
KF25KF40
2¾"CF
1"tube

10 Cold Cathode Ionization Vacuum Sensor
The power supply input may range from 14 to 30 VDC. The positive side of
the power supply is connected to pin 3 and the negative side to pin 4 of the
maleD-subconnector.
Damage may occur to the circuitry if excessive voltage is applied
or if a wrong connection is made.
The analog output voltages are pins 5 (+) and 8 (-). Connect them to a
differentialinputvoltmeteroran analog-to-digital (A/D) converter with a
differential input in a system controller.
Do not connect the negative side of the analog output, pin 8, to
the negative side of the power supply input, pin 4, or to any
other ground. Half of the power current would flow through this
wire. Measurement errors in the output voltage may be seen due
to the voltage drop from this current. The longer the cable, the
worse the error will be.
To enable the high voltage with an external switch, connect pin 9 to the power
supply input (-), pin 4.
An open connection turns off the high voltage. The high voltage should be
turned off at pressures above 10-2 Torr to prevent effects of contamination at
higher pressures. An output of greater than 9.5 V indicates the high voltage is
off and an output of less than 0.5 V indicates no power to the transducer or
that discharge has not yet started.
Connect pin 7 to the power supply input (-), pin 4 to disable the set point relay .
Do not connect the set point relay terminals to the analog output.
Male,9-pinD-subconnector
Pin Description
1 Set point relay - normally open contact
2 Set point relay - normally closed contact
3 Power supply input (+)
4 Power supply input (-)
5 Analog output voltage (+)
6 Set point relay - common
7 Set point relay - disable
8 Analog output voltage (-)
9 High voltage - enable
1
96
5

11
Cold Cathode Ionization Vacuum Sensor
Relay Inductive Loads and Arc Suppression
If the set point relay is used to switch inductive loads, e.g. solenoids, relays,
transformers, etc., the arcing of the relay contacts might interfere with
controlleroperationorreducerelay contact life. Therefore an arcsuppression
network, shown schematically below, is recommended. The values of the
capacitance C and the resistance R can be calculated by the equations,
C = I
2/(1 x 107) and
R = E / I
a
where,
C is in farads
R is in ohms
I is DC or ACpeak
load current in amperes
E is DC or ACpeak
source voltage in volts
a = 1 + (50/ E ).
Note that,
R
min
= 0.5 W and C
min
= 1.0 x 10-9 F.
Relayarcsuppressionnetwork

12 Cold Cathode Ionization Vacuum Sensor
123456789
Pressure(Torr)
OutputVoltage(VDC)
Operating the Series 903 (IMT)
Starting the (IMT)
The (IMT) starts quickly in low vacuum. In the UHV pressure range,
starting may be delayed by several minutes. The SensaVac IgniTorr™
Cold Cathode Starting Device may be used to reduce starting time
(seeAccessories,p.22).
Reading Pressure
To measure nitrogen gas pressure with the (IMT), turn the power on and start
the high voltage. Refer to the graph below, showing pressure as a function of
output voltage for nitrogen. To independently convert voltage to pressure, use
the equation in the next section.
When using the graph, remember that the pressure scale is
logarithmic, and the voltage scale is linear. Equal increments of
distance along the pressure scale do not correspond to equal
pressurechanges.
10-2
10-3
10-4
10-5
10-6
10-7
10-8
10-9
10-10

13
Cold Cathode Ionization Vacuum Sensor
Cold cathode ionization systems are gas dependent and the Series 903
(IMT's) output is defined for air/nitrogen. Refer to page 16, Using the Series
903 (IMT) with Other Gases, to determine the true pressure of another gas.
Equation for Converting Voltage to Pressure
Thefollowingequationconvertsthe(IMT)voltage reading V toapressurereading
P when using air or nitrogen. The voltage must be within the domain of the
equationor anincorrectpressurereading willresult.
Where,
P is in Torr, mbar, microns, or Pascal (depending on K)
V is in volts for 1.5 < V < 8.7
K = 11.000 for Torr, 10.875 for mbar,
8.000 for microns, 8.875 for Pascal.
Using the Set Point
Attach a digital voltmeter to the Common tip jack and the Set Point tip jack
on the (IMT) as shown below. Adjust the potentiometer with a small
screwdriver until the voltage reading coincides with the desired set point
pressure. This pressure is shown on the graph on the previous page or is
calculatedfromtheequationabove.
When the set point LED is on, the measured pressure is below the set
point value, the normally open relay contact is closed, and the normally
closed contact is open. When the LED is off, the measured pressure is
above the set point value, the normally open relay contact is open, and the
normally closed contact is closed. If a power failure occurs, the set point
and its LED will turn off.
Set Point
Potentiometer
TipJacks
Set Point LED
P = 10 (
V-K )

14 Cold Cathode Ionization Vacuum Sensor
The set point can be turned off by connecting pin 7 (set point disable) to pin 4
(powersupplyinput(-)).
If the high voltage is started in high vacuum and the sensor
discharge has not yet begun, the (IMT) will indicate too low of a
reading, possibly tripping the set point. In this case, you should
deactivate the set point, monitor the reading until the sensor
starts,andactivatethesetpointthereafter.
Venting to Atmosphere
Whilethe (IMT)can withstand rapid venting to atmosphere without damage,
prolongedoperation at pressuresabove10-3 Torrincreases thenegative
effects of contamination in the sensor. Contamination can result in
measurementerrorsand,inseverecases,instabilitiesrequiring more frequent
cleaning of the (IMT).
Analog-to-Digital (A/D) Converter
To take full advantage of the (IMT’s) capabilities, an A/D converter with an
input voltage span of 0 to 10 V may be used. A resolution of 12 bits is
needed, corresponding to 2.44 mV per bit. The A/D converter should have a
differentialinputtoensureaccuratemeasurements.
Preparing for Bakeout
Shut off power to the (IMT) and remove its cable. Remove the two Phillips
head screws holding the electronics assembly to the sensor body. The
remainder of the Sensor is ready to be baked out to 400°C if using a CF
flange or to 150°C if using a KF flange.
Leak Detection
Its inherent sensitivity to gas type makes the Series 903 (IMT) useful for
detecting leaks in vacuum systems. It is a good complement to a mass
spectrometer leak detector, which locates smaller leaks.
Probe the suspected leak areas with a gas that has an ionization potential
different than that of the system gas. Helium or argon gas is suitable for
probinga system pumping air or nitrogen.