937B Digital Combination Vacuum Gauge Controller Operation Manual

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MKS
M S Se
eries
s 93
37B
High Vacu
uum
Multi-Sen
nsor S
Syste
em

Opera
O
ation and
a Mainte
M
enanc
ce Ma
anual

1
RevC
Part #: 100016467

Table of Contents
Package Contents .................................................................................................................................. 7
1
1.1
1.2
1.2.1

Safety Information ..................................................................................................................... 8
Symbols Used in this Manual and their definitions ......................................................... 8
Safety Precautions .......................................................................................................... 8
Safety Procedures and Precautions ............................................................................ 8

2
2.1
2.2
2.3

Specifications .......................................................................................................................... 10
Controller ....................................................................................................................... 10
Sensors ......................................................................................................................... 12
Controller Display Messages ........................................................................................ 16

3

Feature, Control Locations and Dimensions ........................................................................... 17

4

Typical Applications for the Series 937B Controller................................................................ 19

5

HPS Products Series 937B Multi-Sensor High Vacuum System .......................................... 20

6
6.1
6.2
6.3
6.3.1
6.3.2
6.4
6.4.1
6.4.2
6.4.3
6.4.4
6.5
6.5.1
6.5.2
6.5.3
6.5.4
6.5.5
6.6
6.6.1
6.6.2
6.6.3
6.7
6.7.1
6.7.2

Operating the Series 937B Controller ..................................................................................... 22
Power ............................................................................................................................ 22
Front Panel Control Lock............................................................................................... 22
Front Panel Display ....................................................................................................... 22
Standard front panel display ...................................................................................... 22
Large font displays ..................................................................................................... 23
System Setup ................................................................................................................ 24
Overview of 937B System setup ................................................................................ 24
Display system setup parameters .............................................................................. 25
Change and save a parameter value ......................................................................... 25
Description of the system setup parameters ............................................................. 26
Channel Setup for Pressure Measurement ................................................................... 30
Overview of 937B Channel setup .............................................................................. 30
Setup for a Capacitance Manometer ......................................................................... 32
Setup for a PR (Pirani)/CP (convection Pirani) sensor .............................................. 34
Setup a Cold Cathode Sensor ................................................................................... 37
Setup a Hot Cathode Sensor ..................................................................................... 40
Power Control of a Pressure Sensor............................................................................. 43
Power (including degas) control of a sensor using front panel control button ........... 43
Power (including degas) control of a sensor via 37 pin AIO Dsub connector ........... 44
Power (including degas) control of a sensor using Serial communication commands.45
Leak Test Using the 937B Controller ............................................................................ 45
Leak test principle applied for the 937B ..................................................................... 45
Procedures for a leak test with the 937B ................................................................... 46

7
7.1
7.1.1
7.1.2
7.1.3
7.1.4
7.1.5

Installing Vacuum Sensors ..................................................................................................... 48
Installing cold cathode sensors ..................................................................................... 48
Locating a Cold Cathode Sensor ............................................................................... 48
Orienting a Cold Cathode Sensor .............................................................................. 48
Managing Contamination in a Cold Cathode Sensor................................................. 48
Connecting the Series 421/422 Sensor ..................................................................... 48
Connecting the 423 I-MAG Sensor ............................................................................ 49

MKS 937B Operation Manual

2

7.2
7.2.1
7.2.2
7.2.3
7.2.4
7.2.5
7.3
7.3.1
7.3.2
7.3.3
7.3.4
7.3.5
7.3.6
7.4
7.4.1
7.4.2

Installing hot cathode sensors ....................................................................................... 49
Locating a Hot Cathode Sensor ................................................................................. 49
Preventing Contamination in a Hot Cathode Sensor ................................................. 49
Orienting a hot cathode sensor .................................................................................. 49
Connecting a Hot Cathode Sensor to the vacuum system ........................................ 49
Connecting a Hot Cathode Sensor to the 937B Controller ........................................ 50
Installing Pirani Sensors ................................................................................................ 52
Locating a Pirani Sensor ............................................................................................ 52
Preventing Contamination in a Pirani Sensor ............................................................ 52
Orienting the Series 317 Pirani Sensor...................................................................... 52
Orienting the Series 345 Pirani Sensor...................................................................... 52
Connecting the Series 317/345 Sensors ................................................................... 52
Preparing the 317 Sensor for Bakeout....................................................................... 54
Capacitance Manometers - MKS Baratron ................................................................... 54
Installing a Baratron Capacitance Manometer ........................................................... 54
Connecting a Baratron™ Capacitance Manometer ................................................... 54

8
8.1
8.1.1
8.1.2
8.1.3
8.2
8.3
8.4
8.4.1
8.4.2
8.4.3

Connecting Relay and Analog Outputs ................................................................................... 56
Connecting 937B relay outputs ..................................................................................... 56
Pin out for the 937B relay output ............................................................................... 56
Proper setting of a relay ............................................................................................. 57
Relay Inductive Loads and Arc Suppression ............................................................. 58
Connecting the 937B Analog Output............................................................................. 58
Buffered analog output .................................................................................................. 59
Logarithmic/Linear and combination analog output ...................................................... 69
Logarithmic/Linear analog output............................................................................... 70
Combination analog output ........................................................................................ 70
Logarithmic/Linear analog output when the gauge power is turned off ..................... 72

9
937B RS232/485 Serial Communication Commands ............................................................. 73
9.1
Communication protocols .............................................................................................. 73
9.2
Pressure reading commands ........................................................................................ 74
9.3
Relay and control setting commands ............................................................................ 75
9.4
Capacitance manometer control commands ................................................................ 76
9.5
Pirani and convection Pirani control commands ........................................................... 76
9.6
Cold cathode control commands ................................................................................... 77
9.7
Hot cathode control commands .................................................................................... 78
9.9
System commands ........................................................................................................ 79
9.10
Error code ...................................................................................................................... 80
9.11
937B ProfiBus communication protocol and commands .............................................. 81
9.11.1
Electrical Connections................................................................................................ 81
9.11.2
ProfiBus GSD protocol ............................................................................................... 81
9.11.3
937 ProfiBus output buffer map ................................................................................. 83
9.11.4
937B ProfiBus input buffer map ................................................................................. 85
10
10.1
10.2
10.3
10.4
10.5

937A Emulated Operation and RS232/485 Serial Communication Commands..................... 88
Operating the 937B controller in 937A emulated operation mode ................................ 88
Communication protocols .............................................................................................. 90
Pressure reading commands ........................................................................................ 91
Relay and control setting commands ............................................................................ 92
Cold cathode control commands ................................................................................... 92

MKS 937B Operation Manual

3

10.6
10.7
10.8

User calibration commands ........................................................................................... 93
System commands ........................................................................................................ 93
ASCII character table .................................................................................................... 94

11
11.1
11.2
11.3
11.4
11.5
11.6

Maintenance of Series 937B Controller modules ................................................................... 95
Removing and Installing a Sensor Module.................................................................... 95
Removing and Installing AIO Module ............................................................................ 96
Communication Module................................................................................................. 97
Power Supply ................................................................................................................ 97
Mounting the 937B controller ........................................................................................ 98
AC Power Cord ............................................................................................................. 99

12
Maintenance and Service of HPS Vacuum Sensors........................................................... 100
12.1
421 Cold cathode sensor ............................................................................................ 100
12.1.1
Cold cathode theory ................................................................................................. 100
12.1.2
Maintenance of Series 421/422 Cold Cathode Sensor............................................ 101
12.2
Maintenance of Series 423 I-MAG® Cold Cathode Sensor ........................................ 104
12.2.1
Connecting the I-MAG Sensor ................................................................................. 104
12.2.2
Disassembling the I-MAG Sensor ............................................................................ 104
12.2.3
Cleaning the I-MAG Sensor ..................................................................................... 106
12.2.4
Assembling the I-MAG Sensor................................................................................. 106
12.2.5
Preparing the Sensor for Bakeout............................................................................ 107
12.3
Maintenance of Low Power Nude and Mini BA hot cathode sensors ......................... 107
12.3.1
Hot cathode theory ................................................................................................... 107
12.3.2
Cleaning the Hot Cathode Sensor ........................................................................... 108
12.3.3
Testing the hot cathode sensor................................................................................ 109
12.4
Maintenance of Pirani Sensors ................................................................................... 109
12.4.1
Theory of a Pirani pressure sensor .......................................................................... 109
12.4.2
Cleaning the Series 345 Sensor .............................................................................. 110
12.4.3
Cleaning the Series 317 Sensor .............................................................................. 111
12.5
Maintenance of Capacitance Manometer ................................................................... 112
12.5.1
Theory of a capacitance manometer ....................................................................... 112
12.5.2
Repairing the Baratron™ Capacitance Manometer ................................................. 113
13

Spare Parts and Accessories ................................................................................................ 114

14
14.1

APPENDIX ............................................................................................................................ 117
Hot cathode gauge gas correction factors .................................................................. 117

15

Product Warranty .................................................................................................................. 120

MKS 937B Operation Manual

4

List of Figures
Figure 3-1 937B front Panel. .................................................................................................................... 17
Figure 3-2 937B rear panel. ..................................................................................................................... 17
Figure 3-3 937B external dimensions (inches). ......................................................................................... 18
Figure 5-1 937B front view. ........................................................................................................................ 20
Figure 6-1 Standard 937B LCD front panel display for pressure measurement under Leak detection
mode. .................................................................................................................................................. 22
Figure 6-2 A comparison between standard display mode and large font display mode for the 937B LCD
display during pressure measurement. .............................................................................................. 24
Figure 6-3 937B system setup parameters, their default values and ranges. ......................................... 24
Figure 6-4 System setup information displayed on 937B LCD screen. ................................................... 25
Figure 6-5 Setting DAC logarithmic and linear analog output..................................................................... 28
Figure 6-6 System firmware and serial number information displayed on 937B LCD screen. ................... 29
Figure 6-11 Hot cathode setup information displayed on 937B LCD screen............................................ 41
Figure 7-1 13 pin D-Sub connector on the back of 937B HC board. ....................................................... 50
Figure 7-2 LPN gauge cable diagram. ..................................................................................................... 51
Figure 7-3 Mini BA gauge cable diagram................................................................................................. 51
Figure 7-4 317/345 cable diagram. .......................................................................................................... 53
Figure 7-5 The wiring diagram for the Capacitance Manometer cable.................................................... 55
Figure 8-1 Definition of the parameters used for relay control................................................................. 57
Figure 8-2 The relay arc suppression network. ....................................................................................... 58
Figure 8-3 Buffered analog output for cold cathode gauges (421/422/423) in N2. .................................. 60
Figure 8-4 Buffered analog output for hot cathode gauges; same as the logarithmic analog output. ..... 62
Figure 8-5 Buffered analog output for a 345 Pirani gauge....................................................................... 63
Figure 8-6 Buffered analog output for the 317 convection Pirani gauge. ................................................ 66
Figure 8-7 Buffered analog output for capacitance manometers. ........................................................... 69
Figure 8-8 Setup screen for setting combination channel parameters. ...................................................... 71
Figure 11-1 Instructions for removing AIO module. ................................................................................. 96
Figure 11-2 Instruction for connecting wire on the back of the power cord receptor. .............................. 97
Figure 11-3 The 937B controller power supply. ....................................................................................... 98
Figure 12-1 A comparison of Inverted Magnetron (left) and Penning (right) cold cathode gauges. ...... 100
Figure 12-2 Electron orbits and ion production in an inverted magnetron. ............................................ 101
Figure 12-3 An exploded view of the 421/422 cold cathode gauge assembly. ..................................... 102
Figure 12-4 An exploded view of the Series 423 I-MAG cold cathode gauge sensor. .......................... 105
Figure 12-5 BA gauge structure and electron process inside the gauge............................................... 108
Figure 12-6 Filament pin locator for LPN and mini BA gauges.............................................................. 109
Figure 12-7 Schematic of a Pirani thermal conductivity sensor. ............................................................ 110
Figure 12-8 Natural convection heater transfer in horizontal (left) and vertical (right) sensor tubes. .... 110
Figure 12-9 Exploded view of a MKS Capacitance manometer sensor. ............................................... 112

MKS 937B Operation Manual

5

List of Tables
Table 6-1 Valid gauges for autozeroing capacitance manometers of different ranges. .......................... 33
Table 6-2 Relative ionization correction factor to N2 for different gases. ................................................ 41
Table 6-3 Pin out for ion gauge remote control. ...................................................................................... 45
Table 7-1 Hot cathode connector pin out. ................................................................................................ 50
Table 7-2 Pin assignment for HC sensor type identification. ................................................................... 51
Table 7-3 Pin out for 317/345 cables. ...................................................................................................... 53
Table 7-4 Pin out of the 9 pin D-Sub connector on CM module. ............................................................. 54
Table 8-1 Pin out for the 937B relay output. ............................................................................................ 56
Table 8-2 Pin out for 937B analog output. ............................................................................................... 59
Table 8-3 Buffered analog output when sensor power is off. .................................................................... 59
Table 8-4 Buffered analog output for the cold cathode gauges (421/422/423) in N2. This is 2.4 higher
than the raw analog output as shown in Table 8-5. ........................................................................... 61
Table 8-5 Equations for Cold Cathode gauges (N2) raw analog output................................................... 61
Table 8-6 Buffered analog output for the 315/345 Pirani sensors. .......................................................... 64
Table 8-7 Equations for the 315/345 Pirani sensors................................................................................. 65
Table 8-8 Buffered analog output for the 317 Convection Pirani sensor. ................................................ 67
Table 8-9 Equations for the 317 Convection Pirani sensor. .................................................................... 68
Table 9-1 937B serial communication wiring diagram. .............................................................................. 73
Table 9-2 937B serial communication command protocol. ........................................................................ 73
Table 9-3 937B pressure reading commands. ........................................................................................... 74
Table 9-4 937B relay and control serial setting commands. ...................................................................... 75
Table 9-5 937B capacitance manometer serial commands..................................................................... 76
Table 9-6 937B Pirani and Convection Pirani control commands. .......................................................... 76
Table 9-7 937B cold and hot cathode control commands. ...................................................................... 77
Table 9-8 937B cold and hot cathode control commands. ...................................................................... 78
Table 9-13 937B system commands. ...................................................................................................... 80
Table 9-14 937B serial communication error codes. ............................................................................... 80
Table 9-15 937B Profibus electrical connections. ....................................................................................... 81
Table 9-16 937B ProfiBus command list..................................................................................................... 82
Table 9-17 937B ProfiBus output buffer map.............................................................................................. 84
Table 9-18 937B ProfiBus input buffer map. ............................................................................................... 87
Table 10-1 Description of pin assignment for adapting 937A 15 pin connector to 937B 25 pin connector
for relay output.................................................................................................................................... 88
Table 10-2 A description of the pin assignments for adapting the 937A 25 pin connector to the 937B 37
pin connector for analog output and gauge control when a dual PR/CM board is installed in slot A. 89
Table 10-3 A description of the pin assignments for adapting the 937A 25 pin connector to the 937B 37
pin connector for analog output and gauge control when a CC board is installed in slot A. .............. 89
Table 10-4 937B serial communication wire diagram. ............................................................................... 90
Table 10-5 The 937A serial communication command protocol.............................................................. 90
Table 10-6 937A pressure reading serial commands. ............................................................................. 91
Table 10-7 The 937A relay and control setting commands. .................................................................... 92
Table 10-8 The 937A cold cathode control commands. .......................................................................... 92
Table 10-9 937A user calibration commands. ......................................................................................... 93
Table 10-10 937A system commands. .................................................................................................... 93
Table 10-11 ASCII character table........................................................................................................... 94
Table 12-1 Resistance readings of a normal HC sensor. ...................................................................... 109
Table 12-2 Bridge resistance value for a normal 345 Pirani sensor. ..................................................... 111
Table 12-3 Resistance values for a normal 317 convection enhanced Pirani sensor. .......................... 112

MKS 937B Operation Manual

6

Package Contents
Before unpacking the 937B high vacuum, multi-sensor system controller, check all
surfaces of the packing material for shipping damage.
Please be sure that the 937B system contains the following items:






1 Series 937B controller (with selected modules installed)
1 female, 25-pin Dsub connector for relay output connection
1 male, 37pin Dsub connector for analog output connection
1 10-foot power cord (US customer only)
1 HPSTM Products Series 937B User’s Manual CD

If any items are missing from the package, call HPS® Products Customer Service
Department at 1-303-449-9861 or 1-800-345-1967.
Inspect the 937B 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.

MKS 937B Operation Manual

7

1 Safety Information
1.1 Symbols Used in this Manual and their definitions
CAUTION: Risk of electrical shock.
CAUTION: Refer to manual. Failure to read message could result
in personal injury or serious damage to the equipment or both.
CAUTION: Hot surface.

Calls attention to important procedure, practice, or conditions.

Failure to read message could result in damage to the equipment.

1.2 Safety Precautions
1.2.1 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 for the 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.

Properly ground the Controller.
This product is grounded through the grounding conductor of the power cord. To avoid electrical shock,
plug the power cord into a properly wired receptacle before connecting it to the product input or output
terminals. A protective ground connection through the grounding conductor in the power cord is essential
for safe operation.
Upon loss of the protective-ground connection, all accessible conductive parts (including knobs and
controls that may appear to be insulating) can render an electrical shock.

Do not substitute parts or modify the 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.

MKS 937B Operation Manual

8

Use proper electrical fittings.
Dangerous voltages are contained within this instrument. All electrical fittings and cables must be of the
type specified, and in good condition. All electrical fittings must be properly connected and grounded.

The Series 937B Controller contains lethal voltages when on.
High voltage is present in the cable and a cold cathode sensor when the Controller is turned on.

Use the proper power source.
This product is intended to operate from a power source that applies a voltage between the supply
conductors, or between either of the supply conductors and ground, not more than that specified in the
manual.

Use the proper fuse.
Only use a fuse of the type, voltage rating, and current rating specified for your product.

Do not operate in explosive environment.
To avoid explosion, do not operate this product in an explosive environment unless it has been specially
certified for such operation.

Service by qualified personnel only.
Operating personnel must not remove instrument covers. Component replacement and internal
adjustments must only be made by qualified service personnel.

Use proper power cord.
Only use a power cord that is in good condition and that meets the input power requirements specified in
the manual.
Only use a detachable cord set with conductors having a cross-sectional area equal to or greater than
0.75 mm2. The power cable should be approved by a qualified agency such as VDE, Semko, or SEV.

MKS 937B Operation Manual

9

2 Specifications1
2.1 Controller
Pressure measuring range2

1 x 10-11 to 2.0 x 10+5 Torr
1 x 10-11 to 2.6 x 10+5 mbar
1 x 10-9 to 2.6 x 10+7 Pa

Relay set point range3
CC (Cold Cathode)

2.0 x 10-10 to 5.0 x 10-3 Torr
2.7 x 10-10 to 6.5 x 10-3 mbar
2.7 x 10-8 to 6.5 x 10-1 Pa

HC (Hot Cathode)

5.0 x 10-10 to 5.0 x 10-3 Torr
6.5 x 10-10 to 6.5 x 10-3 mbar
6.5 x 10-8 to 6.5 x 10-1 Pa

Pirani

2.0 x 10-3 to 9.5 x 10+1 Torr
2.7 x 10-3 to 1.2 x 10+2 mbar
2.7 x 10-1 to 1.2 x 10+4 Pa

CP (Convection Pirani)

2.0 x 10-3 to 9.5 x 10+2 Torr
2.7 x 10-3 to 1.2 x 10+3 mbar
2.7 x 10-1 to 1.2 x 10+5 Pa

CM (Capacitance Manometer)

1% to 95% of the measurement range of the head (e.g. 1 Torr
head is1.0 x 10-2 to 9.5 x 10-1 Torr)

Allowed range within which a control gauge may switch on a cold or hot cathode
Pirani

5.0 x 10-4 to 9.5 x 10-1 Torr
6.5 x 10-4 to 1.3 x 10-1 mbar
6.5 x 10-2 to 1.3 x 101 Pa

CP (Convection Pirani)

2.0 x 10-3 to 9.5 x 10-1 Torr
2.7 x 10-3 to 1.3 x 10-1 mbar
2.7 x 10-1 to 1.3 x 101 Pa

Protection setpoint4
CC & HC

1.0x10-5 to 1.0x10-2 torr, default setting: 5.0x10-3 Torr

Operating temperature range

5° to 40°C

(41° to 104°F)

Storage temperature range

-10° to 55°C (14° to 131°F)

Relative humidity

80% maximum for temperatures less than 31°C, decreasing
linearly to 50% maximum at 40°C

Altitude

2000 m (6561 ft) maximum

Insulation coordination

Installation (Over-voltage) Category II, Pollution Degree 2

1

Design and/or specifications are subject to change without notice.
The measurement range depends upon the sensor options selected.
3
Relay setpoint values are automatically adjusted when pressure unit is changed.
4
The protection setpoint is always enabled in 937B.
2

MKS 937B Operation Manual

10

Power requirement (nominal)

100 - 240 VAC, 50/60 Hz

Mains voltage

Fluctuations not to exceed ±10% of nominal

Power consumption

150 W maximum

Fuse rating, size

2X2A, 250V, Ø 5 mm x 20 mm

Process control relay

12 nonvolatile relays, (4 for each sensor module)

Relay rating

SPDT, 2 A @ 30 V resistive

Relay response

150 msec maximum

Analog outputs5

One Buffered and one Logarithmic/Linear for each channel, up to
two (2) wide-range combination logarithmic outputs. Output
impedance = 100 ohms

Number of channels

up to 6

Front panel controls

Power on-off switch, setup and operational commands can be
accessed via the keypad.

Display

320x240 color QVGA TFT LCD with back lighting.

Pressure units

Torr, mbar, Pascal or microns

Update rate

LCD display is updated 3 times per second. The pressure/flow
signals are updated every 50 msec.

Leak test

25-segment bar graph with a variable rate audio signal

Sensor module slots

3

Sensor modules

channels/module

Cold Cathode
Hot Cathode
Pirani/Convection Pirani
Capacitance Manometer

single
single
dual
dual

COMM/Control modules
ProfiBus
Pressure Control
Computer interface

Serial – RS-232 and RS-485 9600, 19200, 38400,57600,115200
baud rate selectable

Electronic casing

Aluminum

Dimensions (W x D x H)

9½" x 12¼" x 3½" (241 mm x 311 mm x 88 mm)

Size

½ rack, 2U high

Typical weight

8.0 lb (3.6 kg)

CE certification

EMC Directive: 2004/108/EEC
Low Voltage Directive: 73/23/EEC

5

Logarithmic/linear and combined logarithmic analog outputs can be customized using the system setup
manual.
MKS 937B Operation Manual

11

2.2 Sensors
Sensor type
CC (Cold Cathode)

Series 421 and 422 inverted magnetron
Series 423 I-MAG®

HC (Hot Cathode)

Bayard—Alpert (BA) type ionization gauges including HPS MIG
(Miniature Ionization Gauge, or LPN (Low Power Nude), glass
enveloped gauges and UHV nude type.

Pirani

Series 345 Pirani

CP (Convection Pirani)

Series 317 Convection Pirani

(CM) Capacitance Manometer

MKS unheated Baratron® (622A, 623A, 626A, 722A );
MKS 45 C heated Baratron® (624B,D24B, 627B,D27B);
MKS differential Baratron®

Pressure measurement range
CC (Cold Cathode)

1.0 x 10-11 to 1.0 x 10-2 Torr
1.3 x 10-11 to 1.3 x 10-2 mbar
1.3 x 10-9 to 1.3 x 10+0 Pa

HC (Hot Cathode)

1 .0x 10-10 to 1.0 x 10-2 Torr
1.3 x 10-10 to 1.3 x 10-2 mbar
1.3 x 10-8 to 1.3 x 10+0 Pa

HC with UHV type gauge

2 .0x 10-11 to 1.0 x 10-2 Torr
2.3 x 10-11 to 1.3 x 10-2 mbar
2.3 x 10-10 to 1.3 x 10+0 Pa

Pirani

5.0 x 10-4 to 4.0 x 10+2 Torr
6.5 x 10-4 to 5.2 x 10+2 mbar
6.5 x 10-2 to 5.2 x 10+4 Pa

CP (Convection Pirani)

1.0 x 10-3 to 1.0 x 10+3 Torr
1.3 x 10-3 to 1.3 x 10+3 mbar
1.3 x 10-1 to 1.3 x 10+5 Pa

(CM) Capacitance Manometer

Three decades below full scale of head, (e.g., 10 Torr head is1.0
x 10-2 to 1.0 x 10+1 Torr)

Response time (Buffered analog output)
CC

<40 msec6

HC

<50 msec

Pirani, CP

<80 msec

CM

<40 msec

Response time (Log/Lin analog output)
CC

<50 msec

HC

<50 msec

6

A fast response (<3 msec) cold cathode board is also available. Please consult the factory for details.

MKS 937B Operation Manual

12

Pirani, CP

<80 msec

CM

<80 msec

Resolution7
CC & HC

2 significant digits between 10-10 and 10-3 Torr, 1 significant digit
in 10-11 and 10-2 Torr decades

Pirani

2 significant digits between 10-3 and 99 Torr, 1 significant digit
elsewhere within the gauge’s range

CP

2 significant digits

CM

4 significant digits

Repeatability
CC, HC, Pirani, CP

5% of indicated pressure at constant temperature

CM

0.25% of indicated pressure at constant temperature

Calibration gas
CC, HC

Nitrogen, Argon

Pirani, CP

Air/nitrogen, Argon, Helium

CM

Any (gas independent)

Installation orientation
CC, HC, CM, Pirani

Any (port down suggested for pressure sensor)

CP

Body horizontal only

Materials exposed to vacuum may include
CC

Series 421 and 422 – SS 304, Al 6061, silver-copper brazing
alloy, alumina ceramic, Elgiloy®, OFHC® copper
Series 423 – SS 302, SS 304, glass, Al, Inconel X-750®, alumina
ceramic

HC

304 SS, Inconel® X750, glass, tungsten, platinum clad
molybdenum, tantalum, nickel, braze alloy, either yttria coated
iridium or tungsten filament

Pirani

300 series stainless, platinum, alumina ceramic, silver brazing
alloy, nickel 200

CP

300 series stainless, nickel, glass, platinum

CM

Inconel®

Internal volume8
CC

7
8

Series 421and 422 - 1.8 in3 (30 cm3)
Series 423 - 0.9 in3 (15 cm3)

Trailing zeros displayed on LCD screen do not reflect the resolution of the pressure reading.
Volume will vary with the type of vacuum connection selected

MKS 937B Operation Manual

13

HC

Low power nude tube - zero
Mini BA - 1.4 in3 (23 cm3)

Pirani

0.5 in3 (8 cm3)

CP

2.0 in3 (33 cm3)

CM

Type 622A/623A/626A - 0.38 in.3 (6.3 cm3)
Type 722A -0.3 in.3 (4.9 cm3)

Operating temperature range
CC

Series 421 - 0° to 70°C (32° to158°F)
Series 422--Versions available that operate up to 250°C.
Series 423 - 0° to 70°C (32° to158°F)

Pirani & HC

0° to 50°C (32° to 122°F)

CP

10° to 50°C (50° to 122°F)

CM

0° to 50°C (32° to 122°F)

Maximum bakeout temperature (Without controller or cables)
CC

Series 421 – 250°C (482°F) when backshell subassembly
removed, 125°C (257°F) otherwise
Series 422 and 423 – 400°C (752°F) CF flange version only with
magnet removed

HC

60oC with cable attached
300oC max, with CF, cable removed
150oC, with KF and Viton® seal, cable removed

Pirani

50°C (122°F)

CP

100°C (212°F) RF shielded with coated plastic shell installed
150°C (302°F) Partial shell disassembly required
250°C RF shield via aluminum housing

CM

N/A

Radiation (<107 rad)
CC

Series 422 with Lemo connector

CP

317 with aluminum housing

Hot cathode sensitivity
LPN
Mini BA
Glass BA

9 Torr-1 (20%)
12 Torr-1 (20%)
7.5 to 25 Torr-1 (depend upon the sensor design)

Hot Cathode filament type
LPN & Mini BA
Glass BA

Tungsten (W) or Yittria (Y2O3) coated iridium
Tungsten (W), Yittria (Y2O3) coated iridium or
Thoria (ThO) coated iridium

Hot Cathode degas power (E-beam, at grid)

MKS 937B Operation Manual

14

LPN
Mini BA
Glass BA

20 W max
5 W max
50 W max

Ion gauge operating voltages
HC

Grid: 180 VDC (normal operation); up to 600 V during degas
Filament bias: 30 VDC
Filament: 1.8 VDC @ 2A

CC

4.0 kVDC

Hot Cathode X-ray limit
LPN & Mini BA

3x10-10 Torr9

Dimensions
CC

Series 421 and 422 – 2.26.3 in (56160 mm)
Series 423 – 2.63.4 in (6686 mm)

Mini BA

1.12X2.37 in (2860 mm) with 2-3/4” CF flange

LPN

3.3X1.0 in (83 mm25) with 2-3/4 CF flange, can insert into
NW40 tube.

Pirani

1.3X4.4 in (34112 mm)

CP

1.6X4.4 in (41112 mm)

CM

Types 622A, 623A and 626A - 2.64.8 in. (66121 mm)
Type 722A- 1.53.9 in (3899 mm)

Typical Weight (with 2¾” CF Flange)
CC

421and 422 - 2.4 lb (1.1 kg)
423 - 1.8 lb (0.8 kg)

LPN

0.9 lb (0.40 kg) with CF flange

Mini BA

0.816 lb (0.36 kg) with CF flange

Pirani

0.5 lb (0.2 kg)

CP (w/ KF Flange)

0.5 lb (0.2 kg)

Vacuum Connection

9

CC

KF25, KF40, 2-3/4” CF, 8 VCR® -F (1/2”), 1” tubing

LPN

2-3/4” CF (non-rotatable), KF 40

Mini BA

KF16, KF25, KF40, 2-3/4” CF, 1-1/3” mini CF, 3/4”,1” OD tubing

Pirani, CP

KF16, KF25, 1/8” NPT-M with 1/2” compression seal,
8 VCR®-F, 4 VCR®-F, 1-1/3" CF (non-rotatable),
2-3/4” CF (non-rotatable)

CM

KF16, 8 VCR®-F (1/2”), 8 VCO®-F (1/2”),1-1/3” CF (nonrotatable), ½” tube

The hot cathode X-ray limit can be corrected by using a serial command. See section 9.6 for details.

MKS 937B Operation Manual

15

2.3 Controller Display Messages
X.X0Eee

Normal pressure for the Pirani, CP, CC, and HC

X.XXXEe

Normal pressure for the Baratron

OVER

The pressure is over upper limit (for CC and HC when p > protected
setpoint)

ATM

Atmospheric pressure for the Pirani sensor

>1.100Ee

CM pressure is over 10% of the full scale

LO Setpoint

Definition of the parameters used for relay control.

1. Direction
Direction indicates the direction relative to the setpoint when the relay is activated. There are two
choices: ABOVE and BELOW.
When ABOVE is selected, the relay will be activated when the system pressure is higher than the
setpoint. All relays in the 937B are normally open so ABOVE must be selected to close a relay
when the pressure rises above a defined value. For example, the 937B can be used to control a
normally closed roughing by-pass valve in a vacuum system. If the pressure is above certain
value (defined as the roughing pressure), a relay can be activated (i.e. closed) so that power is
sup plied to the solenoid of the NC roughing valve, opening the valve.
When BELOW is selected, the relay will be activated when the system pressure is lower than the
setpoint. A typical application in this case is the control of a high vacuum chamber isolation valve.
Using relay activation in the BELOW mode, a normally closed isolation valve can be opened only
when the system pressure is below its setpoint.
Since an ion gauge (either hot or cold cathode gauge) is turned off when the
pressure is above its protection or control setpoint, only the BELOW direction is permitted
for ion gauges. It is always dangerous to assume that the pressure is above a defined
setpoint when the ion gauge is turned off.
2. Hysteresis
Hysteresis is designed to prevent chattering of the relay. System pressure may fluctuate slightly,
if the hysteresis is set too close to the setpoint value and there is a potential for undesired relay
activation.
For example, when a main high vacuum isolation valve is opened, a small pressure rise may
occur in the vacuum system. If the hysteresis is close to or identical with the pressure setpoint,

MKS 937B Operation Manual

57

th
he controller will
w try to shutt the valve. Su
uch an operattion is detrime
ental to syste
em control and
d
sh
hould be avoiided. The hys
steresis setting must thereffore be highe
er than the settpoint.
Thus, when dirrection is set to ABOVE, th
he hysteresis must be lowe
er than the se
etpoint, while when
he direction is
s set to BELOW, the hysterresis must be
e higher than tthe setpoint.
th
When
W
Direction
n is changed in the 937B controller,
c
ad
default offset vvalue (about 10%) is given
n to
th
he hysteresis to avoid abov
ve-mentioned
d problem. De
epending on the application
n, this value m
may
ne
eed to be opttimized by the
e user.

8.1.3 Relay
R
Indu
uctive Loa
ads and Arrc Suppre
ession
If the set point
p
relay is used to switc
ch inductive lo
oads, e.g., so lenoids, relayys, transforme
ers, etc., arcin
ng of
the relay contacts
c
may
y interfere with
h the controlle
er operation o
or reduce rela
ay contact life. An arc
suppression network, shown
s
schem
matically in Fig
gure 8-2, is th
herefore recom
mmended.

Figure 8-2
8

The rela
ay arc supprression netw
work.

The value
es of the capa
acitance C and the resistan
nce R are calcculated using
g the equation
ns:

C

E
I2
and
; R
10
10 I a

a  1

500
E

D or ACpeak load
l
current i n amperes, E is the DC o
or ACpeak sourrce
where C is in F, R is in , I is the DC
voltage in volts. Cmin = 0.001 F and Rmin = 0.5 .

8.2 Co
onnecting
g the 937
7B Analog
g Output
Analog ou
utputs are outtput via the 37
7-pin connecttor on the bacck of the AIO module. Thesse analog sig
gnals
can be us
sed to for a va
ariety of proce
ess control an
nd other purpo
oses. In particcular, a comb
bined logarithmic
output cap
pability allows
s two sensor outputs to be
e combined, p
providing the ccontroller with
h a much wide
er
pressure measurement range.
Analog ou
utput signals, which can be
e sent to a data acquisition
n system, are available for each sensor.
These sig
gnals can be accessed
a
from
m the 37 pin D-sub
D
female connector on
n the back of the controllerr.
They inclu
ude buffered, logarithmic, and
a combinattion logarithm
mic output. Buffered and log
garithmic ana
alog
outputs arre simultaneo
ously available
e from all sen
nsors. The de tailed assignm
ment for these pins is
described
d in Table 8-2.

MKS 937B
B Operation Ma
anual

58

Pin
1
2
3
4
5
6
7
8
9
10

Description
Buffered Aout A1
Buffered Aout A2
Buffered Aout B1
Buffered Aout B2
Buffered Aout C1
Buffered Aout C2
Log/Lin Aout A1
Log/Lin Aout A2
Log/Lin Aout B1
Log/Lin Aout B2

Table 8-2

Pin
11
12
13
14
15
16
17
18
19
20
21 to 37

Description
Log/Lin Aout C1
Log/Lin Aout C2
Combination Aout 1
Combination Aout 2
Power A1
Power A2/Degas A1
Power B1
Power B2/Degas B1
Power C1
Power C2/Degas C1
Ground

Pin out for 937B analog output.

8.3 Buffered analog output
A buffered analog signal responds immediately to sensor signal changes; it can therefore be used in
critical fast controlling applications.
Buffered analog signals are non-linear and strongly sensor dependent, use these
signals with due caution.
Normal buffered output for the 937B is 0 to 10 V. If a negative buffered voltage is observed, it may be
caused by


No discharge for a cold cathode, or a pressure reading of less than 1x10-11 torr.



Areading below zero for a capacitance manometer (zero adjustment may be required).

The buffered analog outputs for variety of pressure sensors in an unpowered state are shown in Table 83.
Sensor

Buffered Analog Output when power is off

Cold Cathode (CC)

> 10 V

Hot Cathode (HC)

> 10V

Pirani (PR)

0

Convection Pirani (CP)

0

Table 8-3 Buffered analog output when sensor power is off.
A hot cathode gauge uses different emission currents in different pressure ranges and therefore the
analog output depends on the emission current and pressure. To avoid problems, logarithmic analog
output is used as the buffered analog output.
Buffered analog output for the cold cathode, hot cathode, Pirani, convection Pirani and capacitance
manometers are shown in following figures and tables.

MKS 937B Operation Manual

59

Buffered Cold Cathode Analog Output (N2)
(Series 421 and 423)
10

9

8

Output Voltage, V

7

6

5

4

3

2

1

0
10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

Pressure, Torr
Figure 8-3

Buffered analog output for cold cathode gauges (421/422/423) in N2.

MKS 937B Operation Manual

60

10-2

Pressure, Torr
1.0E-11
1.5E-11
2.0E-11
3.0E-11
4.0E-11
6.0E-11
8.0E-11
1.0E-10
1.5E-10
2.0E-10
3.0E-10
4.0E-10
6.0E-10
8.0E-10
1.0E-09
1.5E-09
2.0E-09
3.0E-09
4.0E-09
6.0E-09
8.0E-09
1.0E-08
1.5E-08
2.0E-08
3.0E-08
4.0E-08
6.0E-08
8.0E-08
1.0E-07
1.5E-07
2.0E-07
3.0E-07
Table 8-4

Buffered Vout, V
0.0000
0.3286
0.5634
0.8994
1.1416
1.4585
1.7035
1.8882
2.3241
2.6299
2.9358
3.1342
3.4587
3.6700
3.8409
4.1006
4.2838
4.5248
4.6807
4.8991
5.0452
5.1579
5.3563
5.4924
5.6809
5.8185
6.0096
6.1423
6.2431
6.4281
6.5683
6.7570

Pressure, Torr
4.0E-07
6.0E-07
8.0E-07
1.0E-06
1.5E-06
2.0E-06
3.0E-06
4.0E-06
6.0E-06
8.0E-06
1.0E-05
1.5E-05
2.0E-05
3.0E-05
4.0E-05
6.0E-05
8.0E-05
1.0E-04
1.5E-04
2.0E-04
3.0E-04
4.0E-04
6.0E-04
8.0E-04
1.0E-03
1.5E-03
2.0E-03
3.0E-03
4.0E-03
6.0E-03
8.0E-03
1.0E-02

Buffered Vout, V
6.8993
7.0871
7.2222
7.3247
7.5140
7.6551
7.8469
7.9769
8.1714
8.3064
8.4136
8.6166
8.7446
8.9177
9.0275
9.1665
9.2614
9.3297
9.4255
9.4826
9.5605
9.6076
9.6708
9.7034
9.7325
9.7703
9.7975
9.8340
9.8575
9.8823
9.8997
9.9178

Buffered analog output for the cold cathode gauges (421/422/423) in N2. This is 2.4
higher than the raw analog output as shown in Table 8-5.

Range

Equation
P  exp( 25.3546  3.3941V  0.9901V 2  0.4259V 3 )

V<2.2V

 V  5.7722 
P  exp

 0.1969 
V  4.2157


P  exp

 0.3161  0.0721557V 

2.2 V< V <3.71 V
V>3.71 V

Table 8-5

Equations for Cold Cathode gauges (N2) raw analog output.

MKS 937B Operation Manual

61

Buffered Hot Cathode Analog Output
6

5

Output Voltage, V

4

3

2

1

0
10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

Pressure, Torr
Figure 8-4

Buffered analog output for hot cathode gauges; same as the logarithmic analog
output.

MKS 937B Operation Manual

62

Buffered Pirani Analog Output
(Series 315 & 345)
He

10

N2

9

Ar

8

Output Voltage, V

7

6

5

4

3

2

1

0
10-4

10-3

10-2

10-1

100

101

102

Pressure, Torr
Figure 8-5

MKS 937B Operation Manual

Buffered analog output for a 345 Pirani gauge.

63

103

Pressure, Torr

Buffered N2 Vout, V

Buffered Ar Vout, V

Buffered He Vout, V

1.0E-04
1.5E-04
2.0E-04
3.0E-04
4.0E-04
6.0E-04
8.0E-04
1.0E-03
1.5E-03
2.0E-03
3.0E-03
4.0E-03
6.0E-03
8.0E-03
1.0E-02
1.5E-02
2.0E-02
3.0E-02
4.0E-02
6.0E-02
8.0E-02
1.0E-01
1.5E-01
2.0E-01
3.0E-01
4.0E-01
6.0E-01
8.0E-01
1.0E+00
1.5E+00
2.0E+00
3.0E+00
4.0E+00
6.0E+00
8.0E+00
1.0E+01
1.5E+01
2.0E+01
3.0E+01
4.0E+01
6.0E+01
8.0E+01
1.0E+02
1.5E+02
2.0E+02
3.0E+02
4.0E+02
6.0E+02
8.0E+02
1.0E+03

0.6323
0.6347
0.6372
0.6420
0.6468
0.6563
0.6656
0.6747
0.6970
0.7185
0.7597
0.7985
0.8707
0.9371
0.9988
1.1376
1.2602
1.4727
1.6557
1.9652
2.2254
2.4526
2.9255
3.3095
3.9177
4.3922
5.1070
5.6323
6.0405
6.7597
7.2342
7.8281
8.1874
8.6026
8.8363
8.9862
9.1992
9.3119
9.4294
9.4846
9.5377
9.5638
9.5795
9.6017
9.6146
9.6319
9.6454
9.6693
9.6925
9.7157

0.6324
0.6339
0.6355
0.6385
0.6414
0.6474
0.6533
0.6591
0.6734
0.6875
0.7147
0.7408
0.7905
0.8371
0.8812
0.9824
1.0735
1.2344
1.3751
1.6162
1.8213
2.0015
2.3794
2.6885
3.1815
3.5686
4.1556
4.5898
4.9289
5.5295
5.9282
6.4295
6.7340
7.0869
7.2858
7.4136
7.5950
7.6909
7.7908
7.8398
7.8835
7.9034
7.9149
7.9306
7.9400
7.9539
7.9664
7.9922
8.0200
8.0502

0.6340
0.6362
0.6384
0.6426
0.6469
0.6553
0.6636
0.6718
0.6919
0.7115
0.7490
0.7847
0.8517
0.9138
0.9718
1.1036
1.2211
1.4271
1.6066
1.9148
2.1788
2.4131
2.9143
3.3370
4.0419
4.6294
5.5955
6.3873
7.0651
8.4399
9.5215
11.1701

Table 8-6

MKS 937B Operation Manual

Buffered analog output for the 315/345 Pirani sensors.

64

Range

Equation
Nitrogen

0.63300 torr

 V  3.512 
p  exp

 0.9177 

1.01

V  8.5032  5.372 10 3

Argon
0.56300 torr

 V  3.063 
p  exp

 0.7436 

1.002

V  7.0422  3.789 10 3

Helium
0.63500 torr full scale), the combined analog output will switch to the capacitance manometer.
When a capacitance manometer and an ion gauge are used in combination, the ion gauge pressure will
be used as the combined analog output. The combined output will switch to the capacitance manometer
only when the ion gauge is turned off.
If a Pirani/Convection Pirani and an ion gauges are use in combination, a smoothing formula is used for
-3
-4
the combined analog output where sensor ranges overlap (10 to 10 torr).
To set the combination analog output from the from panel, press the
to change the Set Combination Ch parameter to On. After pressing
shown below:

MKS 937B Operation Manual

70

System
Setup

Enter

button, then move the cursor

, a setup screen will appear, as

Set Combination Channel Parameter
High

Middle

Low

Enable

Combo #1

C2

B1

A1

Enable

Combo #2

NA

NA

NA

Disable

Figure 8-8 Setup screen for setting combination channel parameters.
Once the combination gauges have been properly selected, enable the combined analog output. If invalid
gauge channels are selected, the Enable parameter will stay in the Disabled mode.
The following rules may be used to simplify the gauge combination configuration.









The combination must include as least two pressure gauges.
NA is used as the parameter when no gauge is assigned
If an ion gauge (either cold cathode or hot cathode) is included in the combination, it must be
assigned as the low pressure range gauge (“Low” in Figure 8.8).
If a Pirani or Convection Pirani gauge is included in the combination, it must be assigned as the
middle pressure range gauge (“Middle” in Figure 8.8).
When a Pirani or Convection Pirani is used in combination, only an ion gauge is allowed to be
assigned as the low pressure range gauge.
Only capacitance manometer is allowed to be assigned as the high pressure range gauge.
When multiple capacitance manometers with same full scale ranges are set to combination, the
output are the average of these gauge outputs.

Pay special attention to the selection of the controlling gauge for the ion gauge;
make sure that both gauges are connected to the same vacuum space at all times, (make
sure no valve is present between these gauges). If a valve between these two gauges is
closed, or if these gauges are connected to different vacuum chambers, it may lead not
only to bad combined pressure readings – it can also destroy an ion gauge sensor.
Combination pressure settings can also be accomplished using following serial commands:


Query the pressure

@254PC1?;FF for corresponding pressure on combined Aout 1 and @254PC2?;FF for the pressure
on combined Aout 2.


Set the gauge combination

MKS 937B Operation Manual

71

@254SPC1!HH,MM,LL;FF and @254SPC2!HH,MM,LL;FF . Here, HH, MM and LL are the gauge
channel (A1, A2, B1, B2, C1, C2, NA) corresponding to the gauge assigned to High, Middle, and Low
range pressure gauges.


Query the gauge combination

@254SPC1?;FF and @254SPC2?;FF .


Enable/disable the combined analog output

@254EPC1!Enable;FF and @254EPC1!Disable;FF .

8.4.3 Logarithmic/Linear analog output when the gauge power is turned off
There are time when the power to a pressure gauge (especially an ion gauge) will be turned off during the
operation. The following table shows the expected logarithmic/linear analog output when the gauge power
is turned off or the combined analog output is disabled.

Gauge type

Condition

Logarithmic/Linear analog output

CM

No CM is connected

0V

PR & CP only

Power off, broken filament

>10.5 V

CC & HC only

Power off, broken filament

>10.5 V

Combined

No gauge is assigned

10 V

Table 8-10. The expected logarithmic/linear analog output values when the sensors are
unpowered.

MKS 937B Operation Manual

72

9 93
37B RS
S232/48
85 Serial Com
mmunication
n
Co
omman
nds
9.1 Co
ommunic
cation pro
otocols
Pin

Description
n

2

RS485(-)/R
RS232TxD/(B
B)

3

RS485(+)//RS232RxD/(A
A)

5

Ground

Table 9-1 937B
9
serial communicati
c
ion wiring diiagram.

Cable length with RS23
32 signals
Cable length with RS48
85 signals
Baud rate
e
Characterr format
Query format

Set forma
at

50 ft (15 m)
4000 ft (1200
0 m)
9600, 19200, 38400, 5760
00, 115200
8 data bits, 1 stop bit, No parity, No ha
ardware handsshaking
@?;F
FF
The correspo
onding respon
nse is
@ACK
K;FF
Here, : Address, 1 tto 254
>: Commandss as describe
ed in 10.2 to10
0.7


> Responses as described
d in 10.2 to10.7
For example, to query pre
essure on cha
annel A1, use
e
@003PR1?;FF
esponding ressponse is
and the corre
@003ACK7..602E+2;FF
mand>=PR1
Here, =003; =7.602E+2
2
@!
;F
FF
The correspo
onding respon
nse is
@ACK
K;FF
Here, : address, 1 tto 254
> Commandss as described
d in 10.2 to10
0.7


> Parameter as described in 10.2 to10.7

> Responses as described
d in 10.2 to10.7
For example, to set new b
baud rate, use
e
@001BR!19200;FF
esponding ressponse is
and the corre
@001ACK19
9200;FF
mand>=BR; 
Here, =001; =19200;
>=192000


Table
T
9-2 937B serial com
mmunication
n command protocol.

MKS 937B
B Operation Ma
anual

73

9.2 Pressure reading commands
Command

Function

PRn
(n=1 to 6)

Read pressure
on Channel n

PRZ

Read
pressures on
all channel

PCn
(n=1 or 2)

Read pressure
on channel n
and its
combination
sensor

Response
Meaning
Single Channels
Pressure in selected units for PR, CP, CC & HC
d.d0Eee
(d,e=0 to 9)
Pressure in selected units for CM
d.dddEe
(d,e =0 to 9)
CM, when CM output is negative.
-d.ddEe
(d,e=0 to 9)
Gauge
e(torr/mbar)
e(Pascal)
e(micron)
LO450 torr
ATM
Cold cathode HV is off, or HC/PR/CP power is off.
OFF
HC and CC power is turned off from rear panel
RP_OFF
control
CC or HC startup delay
WAIT
HC off due to low emission
LowEmis
CC or HC is off in controlled state
CTRL_OFF
CC or HC is off in protected state
PROT_OFF
Sensor improperly connected, or broken filament
MISCONN
(PR, CP only)
6 of above,
Same as above
separated by
spaces
Combination Channels
Combined pressure in selected units
d.d0Eee
(d,e=0 to 9)
NAK181

Combination disabled

Table 9-3 937B pressure reading commands.

MKS 937B Operation Manual

74

9.3 Relay and control setting commands
Command
SPm
(m=1 to 12)

Parameter
d.dd Eee
(d,e=0 to 9)

Response
d.dd Eee
(d,e=0 to 9)

SHm
(m=1 to 12)
SDm
(m=1 to 12)

d.dd Eee
(d,e=0 to 9)
ABOVE or
BELOW

d.dd Eee
(d,e=0 to 9)
ABOVE or
BELOW
NAK162

ENm
(m=1 to 12)

SET,
ENABLE,
or CLEAR

SET,
ENABLE,
or CLEAR

SET or
CLEAR
ddd..ddd
(d=0,1,2)
ddd..ddd

SSm
(m=1 to 12)
ENA
SSA

(d=0,1)

Function
Query or set a setpoint for relay m, response with the
current setting value.
If 0 is used as the parameter, the setpoint will be set as
its low limit value.
Query or set a hysteresis for relay m, response with the
current setting value.
Query or set the direction for relay m, response with the
current setting value. For CC and HC, only BELOW can
be selected.
For CC and HC as the relay direction is fixed to
BELOW.
Query or set status for relay m. Response with current
Enable status. ENABLE enables the relay, its status
depends on the pressure and setpoint value, SET forces
relay activation, regardless of pressure, and CLEAR
disable relay.
Query relay setpoint status, SET is activated, and
CLEAR is disabled.
Query the relay status (relay1 relay 2 …relay 12).
0: clear; 1: set; 2: enable.
Query all 12 relay setpoint status (relay1 relay 2 …relay
12).
0: clear; 1: set.

Table 9-4 937B relay and control serial setting commands.

MKS 937B Operation Manual

75

9.4 Capacitance manometer control commands
Command
BTn
(n=1 to 6)
RNGn
(n=1 to 6)

Parameter
ABS or
DIFF
0.01 to
20000

Response
ABS or
DIFF
0.01 to
20000

BVRn
(n=1 to 6)

5 ,10, 1U,
5U, 10U,
1B, 2B

5 ,10, 1U,
5U, 10U,
1B, 2B
OK or NAK

VACn
(n=1 to 6)
ATZn
(n=1 to 6)
AZn
(n=1 to 6)

A1, B1,
A2, B2,
C1, C2, NA

OK or NAK

Function
Query or set the type of capacitance manometer.
Default = ABS.
Query or set the full scale pressure measurement range
for a capacitance manometer. Valid range is from 0.01
to 20000, and default range is 1000 torr.
Query or set the full scale voltage output range for a
capacitance manometer. Here, U means unidirectioanl,
and B meads bidirectional. Default = 10V.
Zero an absolute capacitance manometer on channel n.
Execute only when the signal is less than 5% of the full
scale.
Zero a differential capacitance manometer on channel n.

A1, B1,
A2, B2,
C1, C2, NA

Query or set capacitance manometer autozero control
channel n, or disable autozero (NA). Execute only when
the signal is less than 5% of the full scale.

Table 9-5

937B capacitance manometer serial commands.

9.5 Pirani and convection Pirani control commands
Command
ATMn
(n=1 to 6)
VACn
(n=1 to 6)
AZn
(n=1 to 6)
GTn
(n=1 to 6)
CPn
(n=1 to 6)

Parameter
d.ddE+ee
(ambient
pressure)

Response
d.ddE+ee

OK or NAK
A1, B1,
A2, B2,
C1, C2, NA
Nitrogen
Argon
Helium
ON or OFF

Table 9-6

MKS 937B Operation Manual

A1, B1,
A2, B2,
C1, C2, NA
Nitrogen
Argon
Helium
ON or OFF

Function
Send an atmospheric pressure to perform ATM
calibration. The PR/CP must be at atmospheric pressure
when running ATM calibration.
Zero a PR/CP on channel n. Execute only when the
pressure reading is less than 1X10-2 torr.
Query or set an autozero (CC or HC) control channel n
for a PR/CP, or disable autozero (NA). Execute only
when the pressure reading is less than 1X10-2 torr.
Query or set a gas type for PR/CP on channel n.

Query the channel power status for PR, CP, HC or high
voltage status for CC.
Turn on/off the channel power for PR, CP, HC, or high
voltage for CC).

937B Pirani and Convection Pirani control commands.

76

9.6 Cold cathode control commands
Command
PROn
(n=1, 3, 5)

Parameter
d.dd Eee
(d,e=0 to 9)

Response
d.dd Eee
(d,e=0 to 9)

CSPn
(n=1, 3, 5)

d.dd Eee
(d,e=0 to 9)

d.dd Eee
(d,e=0 to 9)

XSPn
(n=1, 3, 5)
CHPn
(n=1, 3, 5)

ON or OFF

ON or OFF

d.dd Eee
(d,e=0 to 9)

d.dd Eee
(d,e=0 to 9)

A1, B1,
A2, B2,
C1, C2,
OFF
AUTO,
SAFE,
OFF
dd.d
(d=0 to 9)
ON or OFF

A1, B1,
A2, B2,
C1, C2,
OFF
AUTO,
SAFE,
OFF
dd.d
(d=0 to 9)
ON or OFF

Nitrogen
Argon
Helium

Nitrogen
Argon
Helium
W, O, G, P,
C, R

CSEn
(n=1, 3, 5)

CTLn
(n=1, 3, 5)
UCn
(n=1,3, 5)
CPn
(n=1,3, 5)

GTn
(n=1,3, 5)
Tn
(n=1,3, 5)

TDCn
(n=1,3, 5)
FRCn
(n=1,3,5)

d
(d=0 to 9)
d.dd Eee
(d,e=0 to 9)

d
(d=0 to 9)
d.dd Eee
(d,e=0 to 9)

Table 9-7

MKS 937B Operation Manual

Function
Query or set protection setpoint value for ion gauge for
channel n. The valid PRO range is 1x10-5 to 1x10-2 torr.
Default value is 5x10-3 torr.
Query and set control setpoint value for an ion gauge on
channel n. Valid CSP range is 5x10-4 to 1x10-2 torr for
Pirani, and is 2x10-3 to 1x10-2 torr for convention Pirani.
Extend the upper control setpoint range from 1x10-2 torr
to 9.5x10-1 torr.
Query and set control setpoint hysteresis value for an
ion gauge on channel n. Valid CHP range is 5.5x10-4 to
1.1x10-2 torr for Pirani, and is 2.2x10-3 to 1.1x10-2 torr
for convention Pirani. Default value is 1.5X the control
setpoint value.
Query, enable/disable the control channel status for an
ion gauge on channel n.

AUTO: ion gauge can be turned on & off by the
controlling gauge. SAFE, ion gauge can be turned off,
but, not be turned on by the controlling gauge.
Query or set a gas correction factor for a CC gauge on
Channel n. Valid range is from 0.1 to 10.
Query the channel power status for PR, CP, HC or high
voltage status for CC.
Turn on/off the channel power for PR, CP, HC, or high
voltage for CC).
Query or set a gas type for HC/CC on channel n.

Ion gauge status query.
W = WAIT
P = PROTECT
O = OFF
C = Control
G = GOOD
R = Rear panel Ctrl off
Time delay for staring CCG, 3 to 300 secs
Query or set the pressure to trigger fast relay control
output. Only available for special CC board with fast
relay, and the setpoint value needs to between 5x10-3 to
2x10-10 torr.

937B cold and hot cathode control commands.

77

9.7 Hot cathode control commands
Command
PROn
(n=1, 3, 5)

Parameter
d.dd Eee
(d,e=0 to 9)

Response
d.dd Eee
(d,e=0 to 9)

CSPn
(n=1, 3, 5)

d.dd Eee
(d,e=0 to 9)

d.dd Eee
(d,e=0 to 9)

XSPn
(n=1, 3, 5)
CHPn
(n=1, 3, 5)

ON or OFF

ON or OFF

d.dd Eee
(d,e=0 to 9)

d.dd Eee
(d,e=0 to 9)

A1, B1,
A2, B2,
C1, C2,
OFF
AUTO,
SAFE,
OFF

A1, B1,
A2, B2,
C1, C2,
OFF
AUTO,
SAFE,
OFF

1 or 2

1 or 2

20UA
100UA
AUTO20
AUTO100
dd.d
(d=0 to 9)
ON or OFF

20UA
100UA
AUTO20
AUTO100
dd.d
(d=0 to 9)
ON or OFF

dd.d
(d=0 to 9)
ON or OFF

dd.d
(d=0 to 9)
ON or OFF

d
(d=5-240)
Nitrogen
Argon
Helium

6
(d=5-240)
Nitrogen
Argon
Helium
W, O, P, D,
C, R, F, N

CSEn
(n=1, 3, 5)

CTLn
(n=1, 3, 5)

AFn
(n=1,3, 5)
ECn
(n=1,3, 5)

GCn
(n=1,3, 5)
CPn
(n=1,3, 5)

SENn
(n=1,3, 5)
DGn
(n=1,3, 5)
DGTn
(n=1,3, 5)
GTn
(n=1,3, 5)
Tn
(n=1,3, 5)

XRLn
(n=1,3,5)

d.dd Eee
(d,e=0 to 9)

d.dd Eee
(d,e=0 to 9)

Table 9-8

MKS 937B Operation Manual

Function
Query or set protection setpoint value for ion gauge for
channel n. The valid PRO range is 1x10-5 to 1x10-2 torr.
Default value is 5x10-3 torr.
Query and set control setpoint value for an ion gauge on
channel n. Valid CSP range is 5x10-4 to 1x10-2 torr for
Pirani, and is 2x10-3 to 1x10-2 torr for convention Pirani.
Extend the upper control setpoint range from 1x10-2 torr
to 9.5x10-1 torr.
Query and set control setpoint hysteresis value for an
ion gauge on channel n. Valid CHP range is 5.5x10-4 to
1.1x10-2 torr for Pirani, and is 2.2x10-3 to 1.1x10-2 torr
for convention Pirani. Default value is 1.5X the control
setpoint value.
Query, enable/disable the control channel status for an
ion gauge on channel n.

AUTO: ion gauge can be turned on & off by the
controlling gauge (PR/CP). SAFE, ion gauge can be
turned off, but, not be turned on by the controlling
gauge. If no PR/CP exists, this function can not be
enabled.
Query or set active filament for HC.
Query or set emission current.

Query or set a gas correction factor for a HC gauge on
Channel n. Valid range is from 0.1 to 50.
Query the channel power status for PR, CP, HC or high
voltage status for CC.
Turn on/off the channel power for PR, CP, HC, or high
voltage for CC).
Query or set a gas sensitivity for a HC gauge on
Channel n. Valid range is from 1 to 50.
Query the HC degas status
Turn on/off degas
Query and set the HC degas time.
Query or set a gas type for HC/CC on channel n.

Ion gauge status query.
W = WAIT
C = Control
O = OFF
R = Rear panel Ctrl off
P = PROTECT
F = HC filament fault
D = DEGAS
N = No gauge
Query or set the X-ray limit for a HC sensor. The valid
range is from 0 to 1X10-9 torr.

937B cold and hot cathode control commands.

78

9.9 System commands

Command
AD

Parameter
aaa
(aaa=001 to
253)
#

Response
aaa
(aaa=001 to
253)
#

DLY

NONE
EVEN
ODD
Enable
Disable
t msec

NONE
EVEN
ODD
Enable
Disable
t msec

DM

STD or LRG

STD or LRG

LOCK
SPM

ON or OFF
Enable
Disable

ON or OFF
Enable
Disable
T1,T2,T3,T4

BR

PAR

CAL

MT

STn
(n=A, B, C)

U
FDn
(n=1 to 6)
FVn
(n=1 to 6)

S1S2

Unit

Unit
OK
d.dd
(d=0 to 9)

SN
SPCn
(n=1 or 2)

HH,MM,LL

10 digit SN
HH,MM,LL

EPCn
(n=1 or 2)

Enable
Disable

Enable
Disable

DLTn
(n=0 to 6)

LIN or LOG

LIN or LOG

DLAn
(n=0 to 6)

d.dd Eee
(d,e=0 to 9)

d.dd Eee
(d,e=0 to 9)

MKS 937B Operation Manual

Function
Query or set controller address (1 to 253)
254 is reserved for broadcasting. Default = 253.
Query or set baud rate
(valid # = 9600, 19200, 38400, 57600, 115200),
default = 9600.
Query or set the parity for the controller.
Default=NONE.
Enable or disable User Calibration, default =
Enable.
485 time delay, t must  1 for reliable 485
communication. Default = 8 msec.
Display mode: either standard display, or large font
display. Default = STD.
Enable (ON) or disable (OFF) front panel lock
Enable or disable parameter setting, default =
Enable.
Display the sensor module type. T1, T2, T3=(CC,
HC, CM, PR, NC). NC= no connection. T4=(NA, PB,
PC)
Display the connected sensor type on the specified
module (A, B, or C).
S1,S2=CC,PR,CP,CM,MB,GB,LN,24, NG. NC=no
connection.
Pressure unit, Unit=Torr, MBAR, PASCAL, Micron
Factory default for Pirani sensor module. This will
reset the user calibration to factory default.
Firmware version
n=1=Slot A; n=2=Slot B; n=3=Slot C
n=4=AIO; n=5=COMM; n=6=Main
Display the serial number of the unit.
Set or query the combination channel setting.
HH: The channel for HP sensor;
MM: The channel for MP sensor;
LL: The channel for LP sensor.
Valid values for HH, MM, or LL are A1, A2, B1, B2,
C1, C2, or NA. Default is NA.
Enable of disable the combination channel. When
the combination channel is disabled, the output is
10 V.
Query or set the type of DAC linear (LIN, V=A*P) of
logarithmic linear (LOG, V=A*LogP+B) output.
Default setting is LOG.
Query or set the DAC slope parameter A. Default
value is 0.6. Use n=0 for combination output.
Valid range is from 0.5 to 5 when DLT is set to LOG,
and 1E-4 to 1E-8 when DLT is set to LIN.

79

DLBn
(n=0 to 6)

d.dd Eee
(d,e=0 to 9)

d.dd Eee
(d,e=0 to 9)

IU

ON or OFF

ON or OFF

TXT or
CODE

TXT or
CODE

XDL

SEM

Table 9-9

Query or set the DAC offset parameter B. Default
value is 7.2. Use n=0 for combination output.
Valid range is from –20 to 20 when DLT is set to
LOG, and always equals to zero when DLT is set to
LIN.
Force the use of international pressure unit
(Pascal).
Erase the first page of the memory for preparing the
firmware downloading using Sam-BA after power
cycle of the controller.
Set the NAK error code response. An error text
string is returned if it is set to TXT, while an error
code is returned if it is set to CODE.
937B system commands.

9.10 Error code
When serial commands are used in communicating with 937B, an error code will be
returned if an invalid command or an invalid parameter is sent. The error code can be
displayed in either in TXT or CODE mode, and can be selected by using
@254SEM!TXT;FF or @254SEM!CODE;FF command, respectively.
CODE
150
151
152
153
154
155
156
157
160
161
162
163
164
168
169
172
173
175
176
177
178
179
181
182
183
195
199

937B Error Code
TXT
WRONG_GAUGE
NO_GAUGE
NOT_IONGAUGE
NOT_HOTCATHODE
NOT_COLDCATHODE
NOT_CAPACITANCE_MANOMETER
NOT_PIRANI_OR_CTP
NOT_PR_OR_CM
UNRECOGNIZED_MSG
SET_CMD_LOCK
RLY_DIR_FIX_FOR_ION
INVALID_CHANNEL
DIFF_CM
NOT_IN_DEGAS
INVALID_ARGUMENT
VALUE_OUT_OF_RANGE
INVALID_CTRL_CHAN
CMD_QUERY_BYTE_INVALID
NO_GAS_TYPE
NOT_485
CAL_DISABLED
SET_POINT_NOT_ENABLED
COMBINATION_DISABLED
INTERNATIONAL_UNIT_ONLY
GAS_TYPE_DEFINED
CONTROL_SET_POINT_ENABLED
PRESSURE_TOO_HIGH_FOR_DEGAS
Table 9-10

MKS 937B Operation Manual

937B serial communication error codes.

80

9.11 937B ProfiBus communication protocol and commands
9.11.1

Electrical Connections

Pin Number
3
8
6
5

Description
RxD/TxD+
RxD/TxDV+ (+5Vdc)
Ground

Table 9-11 937B Profibus electrical connections.
The address for ProfiBus ranges from 00 to 99 (decimal), and can be selected from two switches on the
rear panel of 937B controller

9.11.2

ProfiBus GSD protocol

The GSD File name is 937B0D72.GSD, the ID Number is 0D72 hex. The ProfiBus commands are a
subset of RS232/485 serial commands, and are listed in the following table.
ProfiBus Command
Autozero Ch A1
Autozero Ch A2
Autozero Ch B1
Autozero Ch B2
Autozero Ch C1
Autozero Ch C2
Gas Type Ch A1
Gas Type Ch A2
Gas Type Ch B1
Gas Type Ch B2
Gas Type Ch C1
Gas Type Ch C2
Front Panel
Set Parameter
Unit
Protection SetPoint Ch A1
Protection SetPoint Ch A2
Protection SetPoint Ch B1
Protection SetPoint Ch B2
Protection SetPoint Ch C1
Protection SetPoint Ch C2
Ctrl Chan For Ch A1
Ctrl Chan For Ch A2
Ctrl Chan For Ch B1
Ctrl Chan For Ch B2
Ctrl Chan For Ch C1
Ctrl Chan For Ch C2
Ctrl SetPoint Ch A1
Ctrl SetPoint Ch A2
Ctrl SetPoint Ch B1
MKS 937B Operation Manual

Equivalent
RS232 Cmd
AUTZ1
AUTZ2
AUTZ3
AUTZ4
AUTZ5
AUTZ6
GT1
GT2
GT3
GT4
GT5
GT6
LOCK
SPM
U
PRO1
PRO2
PRO3
PRO4
PRO5
PRO6
CSE1
CSE2
CSE3
CSE4
CSE5
CSE6
CSP1
CSP2
CSP3

Parameter
Data Byte
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
81

Parameter values/range
Disable
Ch A1, CH A2
Ch B1, CH B2
Ch C1, CH C2
Local Setting
Nitrogen
Argon
Helium
Custom (HC only)
Local Setting
Disable/Enable/ Local Setting
Disable/Enable/ Local Setting
Torr/Mbar/Pascal/ Local Setting
1E-5, 2E-5, 4E-5, 8E-5, 1E-4, 2E-4,
4E-4, 8E-4, 1E-3, 2E-3, 4E-3, 8E-3,
1E-2, Local Setting

Disable/Ch A1/Ch A2/Ch B1/Ch
B2/Ch C1/Ch C2, Local Setting

4E-4, 8E-4, 1E-3, 2E-3, 4E-3, 8E-3,
1E-2, Local Setting

Ctrl SetPoint Ch B2
Ctrl SetPoint Ch C1
Ctrl SetPoint Ch C2
Ctrl Enable Ch A1
Ctrl Enable Ch A2
Ctrl Enable Ch B1
Ctrl Enable Ch B2
Ctrl Enable Ch C1
Ctrl Enable Ch C2
Fast Relay Ctrl Ch A1
Fast Relay Ctrl Ch B1
Fast Relay Ctrl Ch C1
HC degas time Ch A1
HC degas time Ch A2
HC degas time Ch B1
HC degas time Ch B2
HC degas time Ch C1
HC degas time Ch C2

CSP4
CSP5
CSP6
CTL1
CTL2
CTL3
CTL4
CTL5
CTL6
FRC1
FRC3
FRC5
DGT1
DGT2
DGT3
DGT4
DGT5
DGT6

33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

Off/Safe/Auto/ Local Setting

1E-7, 2E-7, 4E-7, 8E-7, 1E-6, 2E-6,
4E-6, 8E-6, 1E-5, 2E-5, 4E-5, 8E-5,
1E-4, Local Setting
3 TO 240

Table 9-12 937B ProfiBus command list.

MKS 937B Operation Manual

82

9.11.3

937 ProfiBus output buffer map
OUTPUT Buffer Map
Offset Size Format
Description
0
1
Bit field Bit 0 Enable / Clear Setpoint Relay 1
Bit 1 Enable / Clear Setpoint Relay 2
Bit 2 Enable / Clear Setpoint Relay 3
Bit 3 Enable / Clear Setpoint Relay 4
Bit 4 Enable / Clear Setpoint Relay 5
Bit 5 Enable / Clear Setpoint Relay 6
Bit 6 Enable / Clear Setpoint Relay 7
Bit 7 Enable / Clear Setpoint Relay 8
1
1
Bit field Bit 0 Enable / Clear Setpoint Relay 9
Bit 1 Enable / Clear Setpoint Relay 10
Bit 2 Enable / Clear Setpoint Relay 11
Bit 3 Enable / Clear Setpoint Relay 12
Bit 4 N/A
Bit 5 N/A
Bit 6 N/A
Bit 7 N/A
2
1
Bit field Bit 0 Power CC/HC/PR Channel A1
Bit 1 Power CC/HC/PR Channel A2
Bit 2 Power CC/HC/PR Channel B1
Bit 3 Power CC/HC/PR Channel B2
Bit 4 Power CC/HC/PR Channel C1
Bit 5 Power CC/HC/PR Channel C2
Bit 6 N/A
Bit 7 N/A
3
1
Bit field Bit 0 Setpoint/Close Mode for MFC on Channel A1
Bit 1 Setpoint/Close Mode for MFC on Channel A2
Bit 2 Setpoint/Close Mode for MFC on Channel B1
Bit 3 Setpoint/Close Mode for MFC on Channel B2
Bit 4 Setpoint/Close Mode for MFC on Channel C1
Bit 5 Setpoint/Close Mode for MFC on Channel C2
Bit 6 N/A
Bit 7 PID control enable/disable
4
1
Bit field Bit 0 Degas HC Channel A1
Bit 1 Degas HC Channel A2
Bit 2 Degas HC Channel B1
Bit 3 Degas HC Channel B2
Bit 4 Degas HC Channel C1
Bit 5 Degas HC Channel C2
Bit 6 N/A
Bit 7 N/A
5
1
Bit field Bit 0 Active Filament Select HC Channel A1
Bit 1 Active Filament Select HC Channel A2
Bit 2 Active Filament Select HC Channel B1
Bit 3 Active Filament Select HC Channel B2

MKS 937B Operation Manual

83

6

1

Bit field

7

1

Bit field

8
12

4
4

Float
Float

16
20

4
4

Float
Float

24
28

4
4

Float
Float

32
36

4
4

Float
Float

40
44

4
4

Float
Float

48
52

4
4

Float
Float

Bit 4 Active Filament Select HC Channel C1
Bit 5 Active Filament Select HC Channel C2
Bit 6 N/A
Bit 7 N/A
Bit 0 Manual Zero PR/CM/MFC Channel A1
Bit 1 Manual Zero PR/CM/MFC Channel A2
Bit 2 Manual Zero PR/CM/MFC Channel B1
Bit 3 Manual Zero PR/CM/MFC Channel B2
Bit 4 Manual Zero PR/CM/MFC Channel C1
Bit 5 Manual Zero PR/CM/MFC Channel C2
Bit 6 N/A
Bit 7 N/A
Bit 0 Factory Default Channel A1
Bit 1 Factory Default Channel A2
Bit 2 Factory Default Channel B1
Bit 3 Factory Default Channel B2
Bit 4 Factory Default Channel C1
Bit 5 Factory Default Channel C2
Bit 6 N/A
Bit 7 N/A
Relay Setpoint Pressure for Relay 1
Relay Setpoint Pressure for Relay 2
Flow Setpoint for Channel A1 (MFC only)
Relay Setpoint Pressure for Relay 3
Relay Setpoint Pressure for Relay 4
Flow Setpoint for Channel A2 (MFC only)
Relay Setpoint Pressure for Relay 5
Relay Setpoint Pressure for Relay 6
Flow Setpoint for Channel B1 (MFC only)
Relay Setpoint Pressure for Relay 7
Relay Setpoint Pressure for Relay 8
Flow Setpoint for Channel B2 (MFC only)
Relay Setpoint Pressure for Relay 9
Relay Setpoint Pressure for Relay 10
Flow Setpoint for Channel C1 (MFC only)
Relay Setpoint Pressure for Relay 11
Relay Setpoint Pressure for Relay 12
Flow Setpoint for Channel C2 (MFC only)

Table 9-13 937B ProfiBus output buffer map.

MKS 937B Operation Manual

84

9.11.4

937B ProfiBus input buffer map
INPUT Buffer Map
Offset Size Format
0
4
Float
4
4
Float
8
4
Float
12
4
Float
16
4
Float
20
4
Float
24
1
Byte

Description
Pressure Channel 1
Pressure Channel 2
Pressure Channel 3
Pressure Channel 4
Pressure Channel 5
Pressure Channel 6
Status for Channel 1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

25

1

Byte

NOGAUGE
NEGATIVE
CONTROL
HI
LO
OFF
AA
PROTECT
WAIT
RP_OFF
Degas
FAULT
OPEN (for MFC only)
CLOSE( for MFC only)
SETPOINT( for MFC only)
PID( for MFC only)
Status for Channel 2

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
26

1

Byte

NOGAUGE
NEGATIVE
CONTROL
HI
LO
OFF
AA
PROTECT
WAIT
RP_OFF
Degas
FAULT
OPEN (for MFC only)
CLOSE( for MFC only)
SETPOINT( for MFC only)
PID( for MFC only)
Status for Channel 3

1
2
3

MKS 937B Operation Manual

NOGAUGE
NEGATIVE
CONTROL

85

4
5
6
7
8
9
10
11
12
13
14
15
16
27

1

Byte

HI
LO
OFF
AA
PROTECT
WAIT
RP_OFF
Degas
FAULT
OPEN (for MFC only)
CLOSE( for MFC only)
SETPOINT( for MFC only)
PID( for MFC only)
Status for Channel 4

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
28

1

Byte

NOGAUGE
NEGATIVE
CONTROL
HI
LO
OFF
AA
PROTECT
WAIT
RP_OFF
Degas
FAULT
OPEN (for MFC only)
CLOSE( for MFC only)
SETPOINT( for MFC only)
PID( for MFC only)
Status for Channel 5

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
29

1

Byte

NOGAUGE
NEGATIVE
CONTROL
HI
LO
OFF
AA
PROTECT
WAIT
RP_OFF
Degas
FAULT
OPEN (for MFC only)
CLOSE( for MFC only)
SETPOINT( for MFC only)
PID( for MFC only)
Status for Channel 6

1

MKS 937B Operation Manual

NOGAUGE

86

30

1

31

1

32
36
40
44
48
52
56
60
64
68
72
76
80

4
4
4
4
4
4
4
4
4
4
4
4
1

81

1

2
NEGATIVE
3
CONTROL
4
HI
5
LO
6
OFF
7
AA
8
PROTECT
9
WAIT
10
RP_OFF
11
Degas
12
FAULT
13
OPEN (for MFC only)
14
CLOSE( for MFC only)
15
SETPOINT( for MFC only)
16
PID( for MFC only)
Bit field Bit 0 Setpoint Relay state Relay 1
Bit 1 Setpoint Relay state Relay 2
Bit 2 Setpoint Relay state Relay 3
Bit 3 Setpoint Relay state Relay 4
Bit 4 Setpoint Relay state Relay 5
Bit 5 Setpoint Relay state Relay 6
Bit 6 Setpoint Relay state Relay 7
Bit 7 Setpoint Relay state Relay 8
Bit field Bit 0 Setpoint Relay state Relay 9
Bit 1 Setpoint Relay state Relay 10
Bit 2 Setpoint Relay state Relay 11
Bit 3 Setpoint Relay state Relay 12
Bit 4 N/A
Bit 5 N/A
Bit 6 N/A
Bit 7 N/A
Float
Relay Setpoint Pressure for Relay 1
Float
Relay Setpoint Pressure for Relay 2
Float
Relay Setpoint Pressure for Relay 3
Float
Relay Setpoint Pressure for Relay 4
Float
Relay Setpoint Pressure for Relay 5
Float
Relay Setpoint Pressure for Relay 6
Float
Relay Setpoint Pressure for Relay 7
Float
Relay Setpoint Pressure for Relay 8
Float
Relay Setpoint Pressure for Relay 9
Float
Relay Setpoint Pressure for Relay 10
Float
Relay Setpoint Pressure for Relay 11
Float
Relay Setpoint Pressure for Relay 12
Byte
Reserved
Byte

Reserved

Table 9-14 937B ProfiBus input buffer map.

MKS 937B Operation Manual

87

10 937A Emulated Operation and RS232/485
Serial Communication Commands
10.1 Operating the 937B controller in 937A emulated operation mode
The 937B controller can be operated in 937A emulated operation mode. In this mode, the user can
employ existing cables and connectors to obtain identical relay control and analog output. However, since
significantly more relays (12 relays for the 937B vs. 5 relays for the 937A) and sensors can be connected
to the 937B controller, different connectors are used on the 937B, and adaptors are required for the
smooth transition.
When setting the 937B to the 937A operation mode, a cold cathode card has to be
inserted into slot A (equivalent to CC in the 937A) to ensure that the communications
commands work properly.
When setting the 937B to the 937A operation mode, only 5 relay channels can be
controlled via the serial communication commands. Channels 1,2,3,4 and 5 in the 937A
serial commands correspond to Channels 1, 5,7,9 and 11, respectively, in the 937B. These
relays are highlighted in blue on the Channel Setup screen. See the details in Table 10-1 for
adapting the 937A’s 15pin Dsub connector to the new 937B 25pin relay output connector.
With the 937B, there is no normally closed relay connection available!

Pin
1
2
9
10
14
15
18
19
22
23
Table 10-1

937B (25 pin Dsub)
Description
Relay 1 NO
Relay 1 Common
Relay 5 NO
Relay 5 Common
Relay 7 NO
Relay 7 Common
Relay 9 NO
Relay 9 Common
Relay 11 NO
Relay 11 Common













Pin
2
9
10
11
12
5
13
14
7
15

937A (15 pin Dsub)
Description
CC NO
CC Common
A1 NO
A1 Common
A2 NO
A2 Common
B1 NO
B1 Common
B2 NO
B2 Common

Description of pin assignment for adapting 937A 15 pin connector to 937B 25 pin
connector for relay output.

An adaptor is required to adapt the 937A Controller 25pin analog output accessory cable to the 937B
37pin Dsub connector. Detailed descriptions of the pin assignment for the adaptor are shown in Table 102.

MKS 937B Operation Manual

88


937B (37pin Dsub)
937A (25pin Dsub)
Pin
Description
Pin
Description

1
Buffered Aout A1
2
Buffered Aout, CC

3
Buffered Aout B1
3
Buffered Aout, A1

4
Buffered Aout B2
4
Buffered Aout, A2

5
Buffered Aout C1
5
Buffered Aout, B1

6
Buffered Aout C2
6
Buffered Aout, B2

7
Log Aout A1
7
Log Aout, CC

9
Log Aout B1
8
Log Aout, A1

10
Log Aout B2
9
Log Aout, A2

11
Log Aout C1
10
Log Aout, B1

12
Log Aout C2
11
Log Aout, B2

13
Combination Aout 1
1
Combination, CC

15
Ion Gauge ON A1
13
CC disable

21-37
Ground
14-24
Ground
t 37

21-37
Ground
25
CC disable return
t 37
Table 10-2 A description of the pin assignments for adapting the 937A 25 pin connector to the
937B 37 pin connector for analog output and gauge control when a dual PR/CM board is installed
in slot A.

937B (37pin Dsub)
Pin
Description
1
Buffered Aout A1
3
Buffered Aout B1
4
Buffered Aout B2
5
Buffered Aout C1
6
Buffered Aout C2
7
Log Aout A1
9
Log Aout B1
11
Log Aout C1
12
Log Aout C2
13
Combination Aout 1
14
Combination Aout 2
15
Ion Gauge ON A1
21-37
Ground
t21-37
37
Ground

















937A (25pin Dsub)
Pin
Description
2
Buffered Aout, CC
3
Buffered Aout, A1
4
Buffered Aout, A2
5
Buffered Aout, B1
6
Buffered Aout, B2
7
Log Aout, CC
8
Log Aout, A1
10
Log Aout, B1
11
Log Aout, B2
1
Combination, CC/B1
9
Combination A/B2
13
CC disable
14-24
Ground
25
CC disable return

Table 10-3 A description of the pin assignments for adapting the 937A 25 pin connector to the
937B 37 pin connector for analog output and gauge control when a CC board is installed in slot A.
When setting the 937B to 937A operation mode, the old 937A communication cable has to
be re-wired. Ddetails are shown in Table 10-3

MKS 937B Operation Manual

89

10.2 Communi
C
ication prrotocols

Description
D

New 9
937B
(232&
&485)

Old 937A
RS
S232

Old 937A
RS
S485

RS485(--)/RS232TxD//(B)

2

3

1

RS485(+
+)/RS232RxD
D/(A)

3

2

9

Ground

5

5

5

Table 10-4
4 937B seriall communica
ation wire dia
agram.
Cable length with RS23
32
signals
Cable length with RS48
85
signals
Baud rate
e
Characterr format
RS232 format

RS485 format

Table 10-5

MKS 937B
B Operation Ma
anual

50 ft
f (15 m)
4000 ft (1200 m)
9600, 19200, 384
400, 57600, 1
115200
8 da
ata bits, 1 stop bit, Even orr No parity, No hardware h
handshaking

The
e correspondin
ng response iis

Here:
ommand>: Commands
C
ass described in
n 11.2 to 11.6
6
: Responses
R
ass described in
n 11.2 to 11.6

>: carriage re
eturn)
For example, to query
q
pressurre on channe
el A1, use P1
1
onding respon
nse is 7.6E+0
02
and the correspo
nd>=P1; 
>=7.6E+02
Here, 
and the correspo
onding respon
nse is OK
>
nd>=RLY2; =OK
>
Here,  in
n front of RS2
232 command
d format as de
escribed
above.
A>
$
$1E
and the correspo
onding respon
nse is OK
>
H);
Herre: attention character=$,, =1 (31H
=ECC4; =O
OK
Plea
ase avoid to use
u 0H to 20H
H as address because theyy are nonprintable charactters.
The
e 937A serial communica
ation comma
and protocol..

90

10.3 Pressure reading commands
Command
Pn
(n=1 to 5)

PZ

Cn
(n=1, 2)

Function

Response
Meaning
Read Single Channel pressure
Read pressure
Pressure in selected units (dEee, with 2
d.dEee
on Channel n
leading spaces, in single digit resolution regions
dEee
only)
(d,e=0 to 9)
Above range of 10ee
HI>Eee
At atmosphere (Pirani only, >400 torr, or
AA_ Eee
equivalent)
Below range of 10ee
LO
Read combination pressure
Read pressure
Pressure in selected units
d.dEee
on channel n and
dEee
its combination
(d,e=0 to 9)
sensor
Above combined range
HI
Below combined range
LO
Sensor missing/misconnected
NOGAUGE!
No ion gauge is assigned to the channel.
Disabled!

Table 10-6

MKS 937B Operation Manual

937A pressure reading serial commands.

91

10.4 Relay and control setting commands
Command
RLYn=d.dEee
RLYn =0
RLYn
(n=1 to 5,
d,e=0 to 9)
RLHn=d.dEee
RLHn
(n=1 to 5
d,e=0 to 9)
CTLn=d.dEee
CTLn =0
CTLn
(n=1,2
d,e=0 to 9)

Function
Set relay setpoint for CH n
Disable relay for CH n
Read setpoint for relay CH n

Response
OK
OUT!
d.dEee

Meaning
Action taken
Value to be set is out of range
Present value in selected unit

Set Hysteresis value for CH n
Read Hysteresis value for
relay CH n

OK
d.dEee

Set control setpoint for an ion
gauge on CH n
Disable control for an ion
gauge on CH n
Query control setpoint for an
ion gauge on CH n

OK
OUT!
d.dEee

Action taken
Present hysteresis value in selected
unit. Default is 1.1X the relay
setpoint value.
Action taken
Value to be set is out of range
Present setpoint value in selected
unit. Valid range is 5x10-4 to 9.5x10-1
torr for Pirani, and is 2x10-3 to
9.5x10-1 torr for convention Pirani.
Not an ion gauge.
CC Channel
PR/CP ctrl Channel
CC
A1, or B1
A
B2
B
A2
Action taken
Value to be set is out of range
Present value in selected unit. The
valid range is 1x10-5 to 1x10-2 torr.
Not an ion gauge.
Action taken
Action taken
0: Inactive (NC closed)
1: Active (NO closed)

NOT ION!
n=1
n=2
n=2

PROn=d.dEee
PROn
(n=1,2,4
d,e=0 to 9)
ERn
XRn
Relays

Set ion gauge protection
setpoint for CH n
Query ion gauge protection
setpoint for CH n

OK
OUT!
d.dEee

Enable setpoint for relay n
Disable setpoint for relay n
Read state of relay 1 to 5

NOT ION!
OK
OK
RlyRRRRR
(R=0,1)

Table 10-7

The 937A relay and control setting commands.

10.5 Cold cathode control commands
Command
ECCn
(n=1,2,4)

Function
Enable CC HV
for CH n

XCCn
(n=1,2,4)

Disable CC HV
for CH n

Table 10-8

MKS 937B Operation Manual

Response
OK
PROTECT!
CONTROL!
OK

Meaning
Action taken
Channel is in protected state.
Channel is in controlled state.
Action taken

The 937A cold cathode control commands.

92

10.6 User calibration commands
Command
ATMn=F
ZEROn=F
(n=2 to 5)

Function
Set channel n atmosphere
or zero calibration to factory
setting

ATMn=U
(n=2 to 5)
ZEROn=U
(n=2 to 5)

Set the pressure on
channel n to ATM (760 torr)
Zero the pressure on
channel n

Table 10-9

Response
OK
NO CAL!
CALLOCK!
OUT!
OK

Meaning
Action taken
This module type cannot be calibrated.
Calibration is locked by the XCA
command
Pressure out of range

OK

937A user calibration commands.

10.7 System commands
Command
EFRONT
XFRONT
FRONT

Function
Enable/Disable front panel

Response
OK

Meaning
Action taken

Read state of front panel
lock
Enable/Disable user
calibration

FP FREE
FP LOCK
OK

Front panel is enabled.
Front panel is disabled.
Action taken

Read state of user
calibration lock
Lock the communication
setting including mode,
baud rate, and address
Read state of
communication lock
Set delay in ms for RS-485
time delay

CALFREE
CALLOCK
OK

User calibration is enabled.
User calibration is disabled.
Action taken

COMFREE
COMLOCK
OK
NOT485!

TD
GAUGES

Read time delay
Read sensor module types
presently installed

VER

Read controller module FW
version

t ms
GaT1T2T3
Tn=2
character
module type
in slot CC, A
and B.
c.cc,m.mm
(c,m=0 to 9)

Change of COMM setting is enabled.
Change of COMM setting is disabled.
Action taken
Communication is not in multidrop
mode.
Time delay is t ms.
Cc: Cold cathode
Pr: Dual Pirani
Cm: Dual capacitance manometer
Nc: No module in slot
Wc: Wrong module in CC slot

ECAL
XCAL
CAL
ECOM
XCOM
COM
Tt
(t=0,1,4,8)

Table 10-10

MKS 937B Operation Manual

c.cc: Controller version
m.mm:

937A system commands.

93

10.8 ASCII
A
cha
aracter table

Ta
able 10-11

MKS 937B
B Operation Ma
anual

ASCII character table.

94

11 Maintenance of Series 937B Controller
modules
There are 3 sensor module slots (A, B, and C) available in the 937B controller. Sensor module plug-in
boards (Pirani/CP, capacitance manometer, cold cathode, hot cathode) can be inserted into any available
slot and the controller will automatically recognize the type of the board in the slot. Typically, 937B
controllers are shipped with customer-specified sensor modules and these are tested at the factory.
To change the factory controller configuration or to remove and adjust the appropriate module, follow the
steps shown below.

11.1 Removing and Installing a Sensor Module

Lethal voltages are present in the controller when it is powered. Disconnect the
power cable before disassembly.

Suitable ESD handling precautions should be followed while installing, configuring
or adjusting the instrument or any modules.

To remove a module for modification,
1. Make sure that the 937B power is off, and that the power cord is disconnected
2. Using a #1 Phillips screwdriver, remove the two screws on the top and bottom of the rear
panel of the sensor module.
3. Use a small, flat-blade screwdriver to gently pry the sensor module away from the rear panel
frame until it slides freely.
4. Carefully slide the module out.
5. Place the module on a static-protected workbench.
To installing a module into 937B,
1. Make sure that the 937B power if off, and that the power cord is disconnected
2. Align the module to fit and slide freely in the card guides, with the internal 32-pin DIN
connector end first.
3. Gently slide the module forward (A, B, or C).
4. Using a #1 Phillips screwdriver, tighten two screws on the top and bottom of the rear panel of
the module.
A sensor module (with 32-pin DIN) can only be inserted into slots A, B or C. It will not
fit into the COMM slot!

MKS 937B Operation Manual

95

11.2 Removing and Installing AIO Module
In the 937B controller, the power cord receptor, the RS232/485 communication 9-pin Dsub connector, the
25 pin Dsub Relay output connector, and the 37-pin Dsub Analog output connector are all mounted on
the same AIO back panel.
To remove the AIO module, use the following procedure:

Lethal voltages are present in the controller when it is powered. Disconnect the
power cable before disassembly.

Suitable ESD handling precautions should be followed while installing, configuring
or adjusting the instrument or any modules.

1. Make sure that the 937B power is off and that the power cord is disconnected
2. Using a #1 Phillips screwdriver, remove the four (4) screws on the four corner of the rear
panel of the AIO module.
3. Place a small, flat-bladed screwdriver at the top right corner of the AIO module (as shown
below) and gently pry the AIO module away from the rear panel frame until it slides freely.

Place flat-blade
screw driver here!

AIO

ANALOG

RELAY OUTOUT

RS232/485

100 - 240 VAC
50/60 HZ
150 WATTS
FUSE: 2.0 AT

Figure 11-1

Instructions for removing AIO module.

4. Pull the AIO board out by about 2 inches (5 cm)
5. Use needle-nose pliers to remove the 3 wires (Blue, Brown, and Green/Yellow) connected to
the back of the power cord receptor
6. Carefully slide the module out
7. Place the module on a static-protected workbench

MKS 937B Operation Manual

96

To install the AIO module, please follow the following procedure:
1. Make sure that the 937B power is off and that the power cord is disconnected
2. Align the module to fit and slide freely in the card guides, with the internal 48-pin DIN
connector end first.
3. Gently slide the module forward, and stop when the back end of the module is about 2 inches
(5 cm) away from the back panel frame.
4. Connect 3 wires to the back of the power cord receptor as show below
Back View of the
Power Cord Receptor
Blue wire

Brown wire
Line

Neutral

Green/yellow
wire
Ground

Figure 11-2

Instruction for connecting wire on the back of the power cord receptor.

5. Gently slide the module forward, and make sure the internal 48-pin DIN connector is
engaged.
6. Using a #1 Phillips screwdriver, tighten four (4) screws on the four corners of the rear panel
of the module.

11.3 Communication Module
The communication module is reserved for future ProfiBus, DeviceNet, or EtherNet communication. At
this time, only ProfiBus communication boards are available.
RS232/485 serial communication is always available on the 937B controller. The 9 pin
D-Sub communications connector is located on the back panel of the AIO/Power module.

11.4 Power Supply
Lethal voltages are present in the controller when it is powered. Disconnect the
power cable before disassembly.

Suitable ESD handling precautions should be followed while installing, configuring
or adjusting the instrument or any modules.

MKS 937B Operation Manual

97

The power supply used on the 937B controller is a 150 Watt, open frame switching power supply. This
power supply is mounted on the right-hand side panel using four screws. Do not remove the power
supply.
Contact HPS™ Products Applications Engineering if it becomes necessary to remove or replace the
power supply.

Figure 11-3

The 937B controller power supply.

11.5 Mounting the 937B controller
The 937B controller was designed for both rack mounting and benchtop use. In both cases, leave at least
1 inch open above the perforated panels to ensure adequate ventilation of the controller. Side clearance
is not required.
To accommodate connectors and cables, leave open about 3 inches of clearance behind the rear panel.
Adhesive backed rubber pads are provided for benchtop use. Remove the adhesive backing from each
pad and apply one to each corner of the bottom surface.
Optional mounting hardware is available for mounting the 937B controller in a 19 inch rack.
Mounting a single 937B controller into a 19" rack (HPS® Part # 100005651)

1. Attach the faceplate (3.5"x5.5") to each side of the 937B front panel using the four 10-32
bolts provided. Secure the bolts with the nuts included in the kit.
2. Secure this assembly to the rack using the ¼" screws provided. It may be necessary to
loosen the 10-32 bolts securing the faceplates in order to align the holes with the
mounting holes on the rack.
Mounting the 937B controller with another ½ rack instrument (HPS® Part # 100007700)

1. Attach the ½ rack instrument to the 937B controller using the small splicing plate and the
four 10-32 bolts provided. The splicing plate is used to connect the front panel of each
instrument together.

MKS 937B Operation Manual

98

2. Secure this assembly to the rack using the ¼"screws provided. It may be necessary to
loosen the 10-32 bolts securing the splicing plate in order to align the holes with the
mounting holes on the rack.
All items in the kit may not be necessary, depending on the mounting configuration.
Contact HPS™ Products Applications Engineering for solutions to other mounting configurations.

11.6 AC Power Cord
The 937B controller includes a standard 100-240 VAC, 50/60 Hz power connection with a female IEC
60320 connector. If the power source is different, use only a harmonized, detachable cord set with
conductors having a cross-sectional area equal to or greater than 0.75 mm2. The power cord should be
approved by a qualified agency such as UL, VDE, Semko, or SEV.

Properly ground the controller and vacuum system.
The 937B Controller is grounded through the ground 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.

Do not exceed the manufacturer's specifications when applying voltage. Electrical
shock may result.

MKS 937B Operation Manual

99

12 Mainte
M
nance and Service
S
e of HP
PS Vacuum
Se
ensors
12.1 421
4 Cold cathode
c
sensor
s
12.1.1

Cold
d cathode theory

Ambient gas
g molecules
s are ionized by a high voltage discharg
ge in cold cath
hode sensorss and gauge
sensitivity
y is enhanced by the prese
ence of a mag
gnetic field. H PS Productss Group’s cold cathode sensors
are not sta
andard Penning sensors in
n that they em
mploy an inve
erted magnetrron design tha
at includes an
n
isolation collector,
c
as shown
s
in Figure 12-1. This makes the se
ensor less su
usceptible to ccontamination
n and
allows a wider
w
range of pressure me
easurement.

Figure 12
2-1

A comp
parison of In
nverted Magn
netron (left) a
and Penning
g (right) cold cathode gau
uges.

Cold cathode ionization
n sensors hav
ve inherent ad
dvantages ovver hot cathod
de sensors. T
These include:


No
N filament to break or burn
n out, which makes
m
the gau
uge immune to inrushes o
of air. As well, it is
re
elatively insen
nsitive to dam
mage due to viibration.



No
N X-ray limit for lower pressure measurements.



No
N adjustmentt for emission current or fila
ament voltage
e is needed.



Degassing
D
is not
n needed.



Properly designed sensor tu
ubes can be cleaned
c
and rreused almosst indefinitely.



one current lo
oop, as comp
pared with a h
hot
The control circuit is simple and reliable, having only o
athode senso
or which has three.
t
ca



Le
ess power co
onsumption en
nables the use of significan
ntly longer ca
ables between
n the controlle
er
an
nd the sensorr.

A cold catthode sensor consists of a cathode and
d an anode wiith a potentiall difference off several kilovvolts
between them.
t
The ele
ectrodes are surrounded
s
by
y a magnet, a
arranged so th
he magnetic ffield is
perpendic
cular to the ele
ectric field. Th
he crossed ellectric and ma
agnetic fields cause electro
ons to follow long
spiral traje
ectories within
n the sensor, increasing th
he chance of ccollisions with
h gas molecules, thereby
providing a significant increase in io
onization efficiency over a h
hot cathode ssensor.
on, a near co
onstant circula
ating electrica
al current is tra
apped by the crossed field
ds in which the
In operatio
collisions between elec
ctrons and res
sidual gas mo
olecules prod uce ions thatt are collected
d by the catho
ode.
onship betwe
een sensor cu
urrent and pre
essure is i
The relatio
MKS 937B
B Operation Ma
anual

100

 kkP n , where i is the sensorr ion current, k is

a constant, P is the pressure, and n is a constant (in the range of 1.00 to 1.15). This equation is valid for
pressures ranging from 10-3 to 10-8 torr, depending on the series resistor used. At pressures around 10-6
torr, the sensitivities of 1 to 10A/Torr are not unusual.
The initiation of electron impact events within a cold cathode sensor depends upon certain chance events
such as field emission or cosmic ray production of the first free electron. Electron-molecule collisions
thereafter produce additional electron/ion pairs during the electrons’ transit between the electrodes. The
discharge rapidly builds to a stable value. Start of the discharge normally requires a very short time at 10-6
torr or above, a few minutes at 10-8 torr, and longer times at lower pressures.
Magnetic field
into the page

Cathode

eAnode
e-

Ion+
e-

Figure 12-2

Electron orbits and ion production in an inverted magnetron.

There are issues that should be considered in the design of cold cathode sensors. For instance, at high
pressures the current increases and sputtering of the cathode can become a problem. A large series
resistor reduces sputtering. Voltage across the tube is pressure dependent in the range between 10-4 to
10-2 torr and this can be used to extend the measurement range of the cold cathode to 10-2 torr. Of the
various electrode configurations possible in cold cathode gauges, it has been found that single
feedthrough cold cathodes can suffer from spurious currents due to insulator leakage and field emission
that mask the small, pressure dependent ionization currents.
HPS Products Group cold cathode sensors use an inverted magnetron with separate feedthroughs for
the anode high voltage and the cathode current. This configuration has a cylindrical cathode, a central
wire anode, and an external cylindrical magnet which provides an axial field. The cathode is isolated from
the grounded metal housing. The inverted magnetron geometry produces more stable signal output, and
also works well to low pressure without risk of extinguishing the discharge
.

12.1.2

Maintenance of Series 421/422 Cold Cathode Sensor

12.1.2.1

Disassembling the Series 421/422 Sensor

The Series 421/422 sensor consists of three subassemblies – the backshell; the internal; and the body
subassemblies. Only the internal and body subassemblies are exposed to vacuum.
To disassemble the sensor, remove the backshell subassembly as follows (Steps 1 through 4 are not
necessary when replacing internal parts):
1. Remove the two 4-40 x ¼" Phillips head SEMS screws
the sensor.

MKS 937B Operation Manual

101

2

and slide the backshell

9

off of

Figure 12-3
3

An explo
oded view of the 421/422 cold cathode gauge assembly.

1

2. Remove th
he two 4-40 x ¼" button he
ead screws
3. Use needle
e nose pliers to pull the #2
22 contact
17

.

MKS 937B
B Operation Ma
anual

102

8

.
carefully off of the ion currrent feedthro
ough

4. Pull the #20 contact 7 off of the 5kV feedthrough 12 taking the entire bulkhead
(do not remove the SHV and BNC connectors from the bulkhead).

4

with it

10

and pull the back flange 13 free.
5. Remove the six ¼-28 x 0.875" socket head cap screws
Note that these screws are silver-plated for lubricity and should be used only once. They may
be re-lubricated with a dry lubricant such as molybdenum disulfide, though new silver-plated
screws are recommended. The copper gasket
CF flange gasket.

24

must be replaced with a standard 21/8"

The cathode and anode assemblies are attached to the flange.
Disassembly should proceed from the bottom to the top of the internal
assembly drawing.
6. To remove the cathode 23 , release the two integral, spring-loaded ears that are hooked over
the shoulder of the ceramic insulating support 19 .
7. Gently pull up on the ear until it just clears the outer diameter of the ceramic insulating
support 19 .
18

Position the small Elgiloy® leaf
used to connect the ion current feedthrough 17
to the cathode. The rotational position of the cathode with respect to the leaf is not critical,
however, be careful not to bend the leaf.
8. Slide the cathode

23

and washer

22

off of the insulating support.

9. The insulating support is captured by the guard bolt
wrench and unscrew the guard bolt from the flange

21
13

. Remove this using a spanner

.

20

There is a small curved spring washer
under the head of the guard bolt. This
spring washer holds the insulating support tight, preloads the guard bolt to resist
unscrewing due to possible vibration, and provides compliance for differential thermal
expansion during bakeout.

12.1.2.2

Cleaning the Series 421/422 Sensor

Depending on the degree of contamination and application of the sensor, the internal parts may be
cleaned — either ultrasonically, with mild abrasives, or chemically.
Do not touch any vacuum exposed part after cleaning unless wearing gloves.
Ultrasonic cleaning should use only high quality detergents compatible with aluminum (e. g.
ALCONOX®). Scrub surfaces with a mild abrasive to remove most contamination. Scotch-Brite™ or fine
emery cloth may be effective. Rinse with alcohol.
Clean aluminum and ceramic parts chemically in a wash (not recommended for semiconductor
processing), such as a 5 to 20% sodium hydroxide solution, at room temperature (20°C) for one minute.
Follow with a preliminary rinse of deionized water. Remove smut (the black residue left on aluminum
parts) in a 50 to 70% nitric acid dip for about 5 minutes.

12.1.2.3

Assembling the Series 421/422 Sensor

To reassemble the sensor, reverse the order of procedures used during disassembly. Note the following
tightening procedure for the guard bolt. The bolt has a 3/8" 40 thread design that is delicate.

MKS 937B Operation Manual

103

1. Finger tighten the guard bolt to compress the spring washer and then back off one turn.
Do not overtighten as this will remove all compliance from the spring washer and possibly
damage the aluminum 3/8"-40 thread.
2. Verify that the anode

14

is well-centered within the bore of the guard bolt.

3. If it is off center, carefully bend it back into position and continue with the assembly.

12.1.2.4

Preparing the Sensor for Bakeout

The 421/422 sensor, including the LEMO connectors in the bulkhead, will withstand bakeout up to 250°C.
Additionally, the sensor may be operated during bakeout if cables and connectors with appropriate
temperature ratings are used. Cables or connectors rated to temperatures less than the bakeout
temperature need to be disconnected from the sensor for bakeout. In applications requiring repeated
bakeouts, the use of bakable connectors and cables is suggested. To prepare the sensor for bakeout up
to 125°C, remove the high voltage and ion current cables only.

12.1.2.5

Testing a Cold Cathode Sensor

HPS cold cathode sensors contain anode and cathode (collector) electrodes. Test the sensor with an
ohmmeter. There should be no shorts between the electrodes or from the electrodes to the sensor body.

12.2 Maintenance of Series 423 I-MAG® Cold Cathode Sensor
12.2.1

Connecting the I-MAG Sensor

Mount the Sensor to a grounded vacuum system.
If the I-MAG Sensor has a CF flange, remove the magnet to allow clearance for bolt installation. When
replacing the magnet, note that it is keyed to the sensor body to protect the feedthrough pins from
damage. The pins should be straight and centered.
For grounding, use a conductive, all-metal clamp to mount a KF 25 or KF 40 flanged sensor body.
Connect the cable to the sensor and to the 937B Controller before turning on your system. Tighten the
thumbscrew on top of the cable to make sure it is securely in place.

12.2.2

Disassembling the I-MAG Sensor

1. Clean tweezers and clean smooth-jaw, needle-nose pliers are required.
2. Turn off the power to the 937B controller.
3. Loosen the thumbscrew on top of the sensor cable and remove the cable.
4. Loosen the two flat head screws
5. Remove the magnet

14

15

.

.

6. Using the smooth-jaw, needle-nose pliers, firmly grab the compression spring
tip closest to the flange.
7. Pull on the compression spring
sensor body

9

3

8

. Continue to pull until the compression spring

) from the sensor body.

MKS 937B Operation Manual

at the

while rotating to free it from the formed groove of the
3

is completely free.

8. With the vacuum port facing up, carefully remove the remaining components (
through

3

104

4

2

1

High Voltage
Feedthrough Pin

Leaf Spring

Figure 12-4

Flathead Screw (2)

15

Magnet

14

Ion Current
Feedthrough Pin

13

Glass Insulator

12

Locating Collar

11

Anode

10

Sensor Body

9

Ground Shield

8

Ceramic Spacer, Small

7

Cathode

6

Grid Washer

5

Ceramic Spacer, Large

4

Compression Spring

3

An exploded view of the Series 423 I-MAG cold cathode gauge sensor.

10

or the leaf spring
Do not bend the anode
pin when assembling or disassembling the Sensor.

MKS 937B Operation Manual

105

1

on the ion current feedthrough

12.2.3

Cleaning the I-MAG Sen
nsor

Depending on the degrree of contam
mination and the application
n of the senso
or, the interna
al parts may b
be
sonically, with
h mild abrasiv
ves, or chemiccally.
cleaned — either ultras
Do not touch any va
acuum-exposed part afte
er cleaning u
unless wearin
ng gloves.
cally clean surfaces using only
o
high qua
ality detergentts compatible
e with aluminu
um (i.e.
Ultrasonic
®
ALCONOX ).
h a mild abras
sive to remov
ve most conta
amination. Sco
otch-Brite™ o
or fine emery cloth may be
e
Scrub with
effective. Rinse with alcohol.

Clean aluminum
a
and ceramic pa
arts chemica
ally in a wash
h such as a 5 to 20% sod
dium
om temperatu
ure (20°C) fo
or one minute
e (not recom
mmended for
hydroxide sollution, at roo
emiconducto
or processin
ng). Follow with
w a prelimi nary rinse w
with deionized
d water. Rem
move
se
sm
mut (the blac
ck residue le
eft on alumin
num parts) in
n a 50 to 70%
% nitric acid d
dip for aboutt 5
minutes.
m
Chemical cleaning
g should not be used to c
clean the ano
ode; mild ab
brasives or
ultrasonic cle
eaning are ac
cceptable.

Do not damage the leaf spring

1

while cle
eaning the S
Sensor.

he cleaning methods
m
descrribed above should
s
be follo
owed with mu
ultiple rinses o
of deionized w
water.
Each of th
Dry all inte
ernal compon
nents and the
e sensor body
y
spacers, 4 and
absorbed water.

12.2.4

7

9

in a clea
an oven set a
at 150°C. The
e two ceramicc

, are slightly porous
p
and will
w require lon
nger drying tim
me in the oven
n to drive off tthe

Asse
embling th
he I-MAG Sensor
Wear glloves and as
ssemble with
h clean tools .

1. Roll
R the sensor body
po
ort, check the
e anode

9
10

on
n a flat surfac
ce and, lookin g down the
fo
or any radial runout motion
n. It should be
e

sttraight and ce
entered with th
he sensor body
2. In
nstall the grou
und shield
grround shield

8

8

hield
sh

drops into
o the locating
g collar
7

11

.

over the
t small end of the ground

.

4. Check
C
that the
e leaf spring
6

for prroper operatio
on.

using tweez
zers. Make su
ure that the

3. Slide the smalll ceramic spa
acer
8

9

1

will contac
ct the base off the cathode

, as shown to the right. If
I not, remove
e the small ce
eramic spacerr

MKS 937B
B Operation Ma
anual

106

7

and the ground shield

8

, and gently bend the leaf spring

then replace the ground shield
5. Slide the cathode
5

grid washer

6

8

and ceramic spacer
5

, the grid washer

7

1

towards the anode

4

into place. The

has a concave shape. Refer to the figures to see its installation orientation.
3

9

into the sensor body

7. Using your thumbs, push the larger end of the spring into the sensor body
within the tube's inside diameter.
8. Using the smooth-jaw, needle-nose pliers, work the compression spring
body

and

.

, and the large ceramic spacer

6. Insert the small end of the compression spring

9

10

3

.
9

until it is contained

down into the sensor

until it is fully seated in the formed groove.
8

9. Inspect the ground shield
the anode

10

and the grid washer

5

to verify they are centered with respect to

.

10. If adjustment is needed, gently reposition the grid washer/cathode assembly, taking care not to
scratch the grid washer

5

.

It is recommended that the resistance between the ion current feedthrough pin
5

1

13

and the grid washer

6

be measured to verify that the leaf spring
is in contact with the cathode
. The measurement
should indicate a short circuit between them. There should be an open circuit between the ion current
feedthrough pin

13

and both the high voltage feedthrough pin

2

and the sensor body

9

.

Once this procedure is complete, the I-MAG Sensor is ready for installation. If it is not to be installed
immediately, cover the flange with clean, vacuum grade aluminum foil and cap with a flange protector.

12.2.5

Preparing the Sensor for Bakeout

To prepare the sensor for bakeout at up to 400°C, remove the sensor cable and magnet assembly as
described in "Disassembling the I-MAG sensor".

12.3 Maintenance of Low Power Nude and Mini BA hot cathode
sensors
12.3.1

Hot cathode theory

Hot cathode ionization gauges use the electrons emitted from a hot filament (thermionic electrons) to
create ions in a surrounding gas. The ion numbers are in proportion to the ambient gas pressure.
Electrons are accelerated through the gauge by a potential difference between the hot, emitting filament
and a positively charged surrounding grid (anode). The energy acquired by the electrons as they are
accelerated by the electric field in the gauge is sufficient to ionize resident ambient gas molecules. The
positively charged ions created by this collision ionization are attracted to the negatively biased ion
collector within the gauge where they are neutralized by an electron current. The gas molecules are
singly ionized and there is a one–to-one correspondence between the number of ions neutralized and the
magnitude of the neutralizing electron current. Hence the electron current is often called the “ion current”
and this is proportional to the pressure in the gauge. The “ion current” is measured by the electrometer
and converted to a pressure indication on 937B display.
The Bayard Alpert (BA) gauge is one of the most popular types of hot cathodes gauges. They are
available in glass envelopes, or mounted on a flange (the latter configuration is often referred to as a

MKS 937B Operation Manual

107

nude gaug
ge). The main
n advantage of
o the BA con
nfiguration is iits reduced su
usceptibility to
o X-ray inducced
errors. Th
his is achieved
d through the adoption of a small diame
eter ion collecctor that minim
mizes the area
exposed to
t the soft X-rray emitted fro
om the grid. X-ray
X
emissio
on from the grrid is an undesirable side e
effect
of electron
n impact upon
n the grid surface since so
ome of these X
X-ray strike th
he ion collecto
or, releasing
electrons by the photoe
electric effectt. This photoe
electric curren
nt is not relate
ed to the pressure but is
ess added to the measurement of curre
ent determine d by the electtrometer. The
e photoelectric
neverthele
current ca
an fully mask the ion curren
nt at low pres
ssure (around
d 1x10-10 torr) and this limitts the pressurre
measurem
ment capabilitties of the BA
A gauge.
Ion Colle
ector
Elecctron
Collector
(Grid
d)

Electron Source
e
(Filament)

+30V

A

Figure 12-5

+180V

BA gau
uge structure
e and electro
on process inside the ga
auge.

The collec
ction ion curre
ent i is relatted to the pressure

P and emission currrent i by thee equation

i  kPi where, k is the gauge seensitivity which depends sttrongly upon tthe gauge strructure and
operating condition. Ty
ypical gauge sensitivity forr nitrogen is a
around 7.5 to 15 Torr-1.
e the outgassing in gauge to a negligible
e level, and m
minimize the e
effect of ESD (electron
To reduce
stimulated
d desorption) on high vacu
uum measurement, high te mperature de
egassing tech
hniques are used
to drive offf any adsorbe
ed gas molec
cules from the
e surface of th
he anode grid
d. Electrode h
heating during
g the
degas pro
ocess is accomplished eith
her by electron
n bombardme
ent (EB degass) or by passing a high currrent
through th
he grid (I2R de
egas). EB deg
gas technique
e is accomplisshed in the 93
er by increasin
ng the
37B controlle
emission current from the
t hot cathode.

12.3.2

Cleaning the Hot
H Catho
ode Senso
or

Roughing pump oils an
nd other fluids
s that condense and/or deccompose on ssurfaces with
hin the gauge (i.e.
c
surfa
aces) contamiinate the sens
sor and can ccause calibrattion shift. Deg
gassing of the
e
grid and collector
gauge can
n remove surface contamination on the of grid and ccollector, how
wever, severe contamination of
the grid sttructure may require a replacement of th
he sensor.
Although the feedthrou
ugh insulators
s are shielded
d, in some app
plications con
nducting filmss or other form
ms of
y conductive pathways ma
ay be formed on insulator ssurfaces. Wh
hen this happe
ens it createss a
electrically
leakage path
p
on the ins
sulator that ca
an produce fa
alse low presssure reading. In these casses the senso
or
may have
e to be replace
ed.
Unlike with
w
cold catthode gauge
e, it is not adv
visable to th
he clean the h
hot cathode
ensor. Attem
mpts to clean
n the sensor it may eitherr deform or b
break the gau
se
uge structurre.

MKS 937B
B Operation Ma
anual

108

12.3.3

Testing the hot cathode sensor

This test will only identify a non-functional sensor. It will not detect damage from
contamination, misuse or rough handling that can affect the calibration of a hot cathode
gauge.
The most common cause of sensor failure is filament failure. To check for this failure mode, test the
sensor using an ohmmeter with less than 5 mA of current. The resistance readings of a normal hot
cathode sensor are show in table 12-1. The resistance between the two pins of each filament is of
particular importance. This test may be applied to any hot cathode sensor operated by 937B.
Pin Numbers
Between F1 pins
Between F2 pins
Any pin to ground/shell
Table 12-1

Resistance ( ) for a good
sensor
0-5
0-5
>106

Resistance ( ) for a bad
sensor
Open (>100 )
Open (>100 )
<106

Resistance readings of a normal HC sensor.

F1 and F2 are identified on the Low Power Nude gauge. For a Mini BA, use the drawing in Figure 12-6 to
located F1 and F2.
F2

F1

Locator
Key Slot

Figure 12-6

Filament pin locator for LPN and mini BA gauges.

12.4 Maintenance of Pirani Sensors
12.4.1

Theory of a Pirani pressure sensor

Both standard Pirani and convection enhanced Pirani gauges can be used with the 937B Controller. In
both cases, measurement is based on gas-dependent thermal conductivity of the gas in the vacuum
environment. A wire suspended from supports (as shown in Figure 12-7) is heated and maintained at a
constant temperature during the measurement process.

Heated Wire

To Vacuum
System

MKS 937B Operation Manual

109

Electrical
Leads

Figure 12-7

Schematic of a Pirani thermal conductivity sensor.

The amount of heat exchanged between the hot wire and cold environment is a function of the pressure
when the distance between the hot wire and the cold environment is comparable to the mean free path of
the gas molecules (less than about ~20X of the mean free path). When gas pressure is higher, the gas
thermal conductivity becomes pressure insensitive and natural convective heat transfer must be
employed to improve the gauge sensitivity. This demands the horizontal placement of the sensor tube (as
shown in Figure 12-8) for a convention enhanced Pirani used to measure pressures greater than 100 torr.

Figure 12-8

Natural convection heater transfer in horizontal (left) and vertical (right) sensor
tubes.

The size (diameter) of gas molecules has significant impact on the Pirani sensor. Since smaller molecules
(such as helium) move faster in the gas, this gas can transfer more heat energy under the same pressure
as compared with a gas composed of heavy molecules (e.g. Argon). This explains why helium is
saturated when the pressure is less than 10 torr.
The standard Pirani sensor will read continuously between 5 x 10-4 to 100 Torr, and, with lower
resolution, up to atmospheric pressure.
The Convection Pirani sensor design enhances heat transfer at higher pressures through convection.
This sensor will read continuously with full resolution from 1.0 x 10-3 to 1000 Torr.

12.4.2

Cleaning the Series 345 Sensor

Roughing pump oils and other fluids condensing or decomposing on the heated filament can contaminate
the sensor. This changes the emissivity of the filament, which in turn can cause the calibration to change,
especially at low pressure.

It is not advisable to clean the sensor. Attempts to clean it may either deform or
break the filament. The deformed filament can cause gauge errors arising from a shift in
the sensor output.
Replace the sensor if it becomes contaminated (see Spare Parts and Accessories).

MKS 937B Operation Manual

110

12.4.2.1

Testing the Series 345 Sensor

This procedure tests function only. Lower levels of sensor damage that are due to
contamination or rough handling can affect calibration, but the tube may still be
functional.
The most common cause of sensor failure is a broken filament (checked from pin 4 to pin 6) due to
improper handling.
Test the sensor using an ohmmeter with less than 5 mA of current. The resistance readings of a normal
Series 345 Sensor measured at atmospheric pressure and at room temperature (20°C) are shown in
Table 12-2.
345 D-Sub Pin #
4 to 7
4 to 8
6 to 7
6 to 8
5 to 6
3 to 5
Table 12-2

12.4.3

Resistance ( )
39
114
31
114
62
345

Bridge resistance value for a normal 345 Pirani sensor.

Cleaning the Series 317 Sensor

Roughing pump oils and other fluids condensing or decomposing on the heated filament can contaminate
the sensor. This changes the emissivity of the filament, which in turn can cause the calibration to change,
especially at low pressure.

It is not advisable to clean the Sensor. Attempts to clean it may either deform or
break the filament. The deformed filament would then cause additional error due to a shift
in the sensor's output.
Replace the sensor if it becomes contaminated (see Spare Parts and Accessories).

12.4.3.1

Testing the Series 317 Sensor

The most common cause of sensor failure is a broken filament. This might be caused by physical abuse
or sudden venting of the sensor to atmosphere at the inlet port.
1. Using a #1 Phillips head screwdriver, remove the two screws to separate the
connector/electronics subassembly from the end of the sensor.
2. Check the resistance on the sensor's pins listed in the first column in Table 12-3. Test the sensor
using an ohmmeter with less than 5 mA of current. The resistance readings for a normal sensor
measured at atmospheric pressure and at room temperature (20°C) are listed in the middle
column. If the condition shown in the right column exists, the sensor should be replaced.

12.4.3.2

Preparing the 317 Sensor for Bakeout

Remove the cable from the sensor. Using a #1 Phillips head screwdriver remove the two screws at the
end of the connector/electronics subassembly to separate it from the sensor. The standard Convection
Pirani sensor can be baked up to 150°C and the Shielded Convection Pirani sensor can be baked up to
100°C.
A 317 sensor is also available with an aluminum housing. With the electronics removed, It is bakable to
250°C.

MKS 937B Operation Manual

111

Check
F1 to F2

Resistance ( )

Results

20

If higher, filament is broken or
burned out.

>20x106

If lower, sensor is damaged or
contaminated.

TC1
F1

F1 to sensor port
F2 to sensor port

F2
TC2

TC1 to TC2
Sensor Tube

27

TC1 to sensor port

>20x106

TC2 to sensor port
Table 12-3

If higher, temperature
compensation winding is
broken.
If Lower, temperature
compensation winding is
broken.

Resistance values for a normal 317 convection enhanced Pirani sensor.

12.5 Maintenance of Capacitance Manometer
12.5.1

Theory of a capacitance manometer

Figure 12-9

Exploded view of a MKS Capacitance manometer sensor.

MKS capacitance manometers contains a sensor and signal conditioner. The sensor is made up of a
tensioned metal diaphragm, one side of which is exposed to the media whose pressure is to be
measured. The other (reference) side contains an electrode assembly placed in a reference cavity (see
Figure 12-9). Absolute transducers have the reference side factory-sealed under high vacuum (10-7 torr).
The diaphragm deflects with changing pressure — force per unit area — causing a capacitance change
between the diaphragm and the adjacent electrode assembly. The high level output signal, current, or DC
voltage is linear with pressure, amplified, and self-compensated for thermal stability with ambient
temperature changes. Capacitance manometers should be zeroed on installation. This zero adjustment
has no effect on the actual calibration.

MKS 937B Operation Manual

112

12.5.2

Repairing the Baratron™ Capacitance Manometer

Repair by the user is not recommended since replacement or movement of PC board components may
require complete calibration of the unit. Return to MKS for repair.

MKS 937B Operation Manual

113

13 Spare Parts and Accessories
Part #
Accessories
USA power cable
Half rack mounting kit
Full rack mounting kit
937B Instruction Manual
Rebuild kit for Series 421
Spanner Wrench for 421 tube rebuild
Rebuild kit for Series 423 I-MAG®
Adapter, SMA-F to BNC-M
Adapter, Connector, SMA-M to BNC-F
Fuse (2X) inside the inlet power connector

103150001
100005651
100007700
100016467
100006734
100005279
100002353
100016120
100016121
100015755

Module, plug-in
Cold Cathode
Hot Cathode (MIG/LPN)
Dual Capacitance Manometer/Piezo
Dual Standard Pirani/Convection Pirani
ProfiBus

100015185
100015641
100015267
100015132
100015940

Serial Firmware Download Adaptor
Adaptor

100016642

Cable for Capacitance Manometer, Type 722B
10 ft (3.0 m)
25 ft (7.6 m)
50 ft (15.2 m)

100016951
100016952
100016953

Cable for Capacitance Manometer, Type 626B/627D
10 ft (3.0 m)
25 ft (7.6 m)
50 ft (15.2 m)
Custom to 50 ft (15.2 m)

100007555
100007556
100007557
100007558

Cable for Cold Cathode Sensor, Series 431
10 ft (3.0 m)
25 ft (7.6 m)
50 ft (15.2 m)
100 ft (30.5 m)
Custom to 300 ft (91.4 m)

100016217
100016218
100016219
100016220
100016221

Cable for Cold Cathode Sensor, Series 423 I-MAG®
2 ft (0.6 m)
10 ft (3.0 m)
25 ft (7.6 m)
50 ft (15.2 m)
Custom to 300 ft (91.4 m)

100016295
100016296
100016297
100016298
100016299

Cable for Hot Cathode, Mini BA Gauge
10 ft (3.0 m)
25 ft (7.6 m)
50 ft (15.2 m)

100011106
100011107
100011108

Cable for Hot Cathode, Low Power Nude
10 ft (3.0 m)
25 ft (7.6 m)
50 ft (15.2 m)

100010909
100010910
100010911

Cable for 317 Convection Pirani & 345 Pirani Sensor
10 ft (3.0 m)
25 ft (7.6 m)
50 ft (15.2 m)

103170006SH
103170007SH
103170008SH

MKS 937B Operation Manual

114

100 ft (30.5 m)
Custom to 500 ft (152.4 m)

103170017SH
103170009SH

Cable for Series 902 Transducer
10 ft (3.0 m)
25 ft (7.6 m)
50 ft (15.2 m)
Custom (maximum length 50 ft)

100011869
100011870
100011871
100011872

Capacitance Manometer
626B/627B with male Type D connector
Range torr (XXX)
0.1
1
2
10
20
100
500
1000
Fitting (Y)
1/2” tube
Swagelok 8 VCR female
Mini-CF, rotatable
NW 16 KF
Swagelok 8 VCO female
2-3/4” CF, rotatable
NW 25 KF
Accuracy (Z)
Std, 0.25% of Rdg (optional 0.1 torr)
Std, 0.50% of Rdg, 0.1 torr
Optional: 0.15% of Rdg
(10, 100, 1000T only)

626BXXXYZ/627BXXXYZ
.1T
01T
02T
11T
21T
12T
52T
13T
A
B
C
D
E
L
Q
E
F
D

722B Compact Absolute Capacitance Manometer
Range torr (XXX)
10
100
1000
10000
Fitting (YY)
1/2” tube
Swagelok 4 VCR female
Swagelok 8 VCR female
Swagelok 8 VCO female
mini CF, rotatable
NW 16 KF
Input/Output (W)
+13 to +32 VDC input, 0-10 VDC output
Accuracy (G)
Std, 0.5% of Rdg
Connector (Z)
9-pin Type D

722BXXXYYWGZ
11T
12T
13T
14T
BA
CD
CE
DA
HA
GA
2
F
A

Sensor, Series 431 Cold Cathode
KF 25
KF 40
2¾" CF
1" tube
8 VCR®-F (½")

104310004
104310001
104310002
104310003
104310005

Sensor, Series 423 I-MAG® Cold Cathode
KF 25

104230004

MKS 937B Operation Manual

115

KF 40
2¾" CF
1" tube

104230001
104230002
104230003

Sensor, Hot Cathode MIG Gauge, Yr Coated Ir filament
1” OD tube
Mini CF
2¾" CF
KF 25
KF 40
KF 16
3/4" OD tube

100011085
100011111
100011112
100011113
100011114
100011118
100011127

Sensor, Hot Cathode, Low Power Nude
KF 40, W filament
2¾" CF, W filament
KF 40, Yr coated Ir filament
2¾" CF, Yr coated Ir filament

100005987
100005980
100006841
100006842

Sensor, Convection Pirani, Shielded (317)
KF 16
KF25
1/8" NPT-M with ½" Compression Seal Option
8 VCR®-F (½")
4 VCR®-F (¼")
11/3" CF (non-rotatable)
2¾" CF (non-rotatable)
Ø 15 mm x 30 mm Tubing
Ø 18 mm x 30 mm Tubing

103170010SH
103170027SH
103170011SH
103170012SH
103170029SH
103170013SH
103170014SH
103170016SH
103170018SH

Sensor, Pirani (345)
KF 16
1
/8" NPT-M with ½" Compression Seal Option
8 VCR®-F (½")
11/3" CF (non-rotatable)
2¾" CF (non-rotatable)
KF25
Ø 15 mm x 30 mm Tubing
Ø 18 mm x 30 mm Tubing

103150010
103150011
103450012
103450013
103450014
103450015
103450016
103450018

Sensor, Series 902 Piezo Transducer
902 Transducer, NW16KF, RS485
902 Transducer, 4 VCR®-F, RS485
902 Transducer, 8 VCR®-F, RS485
902 Transducer, NW16KF, RS232
902 Transducer, 4 VCR®-F, RS232
902 Transducer, 8 VCR®-F, RS232
902 Transducer, NW16KF, 0-10V
902 Transducer, 4 VCR®-F, 0-10V
902 Transducer, 8 VCR®-F, 0-10V

902-1112
902-1212
902-1312
902-1113
902-1213
902-1313
902-1105
902-1205
902-1305

Please call the HPS® Products Customer Service Department of MKS Vacuum Products Group at 1-303-449-9861 or
1-800-345-1967 to order any of these parts or to receive catalogs for other MKS products.

MKS 937B Operation Manual

116

14 APPENDIX
14.1 Hot cathode gauge gas correction factors
Substance

Acetaldehyde
Acetone

Formula

Relative ionization
Gas correction factor

C2H4O

2.6

(CH3)2CO

3.6

4.7

4.0

4.8

3.6
Acetylene

C2H2

Air

Substance

Carbon disulfide

Carbon monoxide

Formula

Relative ionization
Gas correction factor

CS2

5.0

CO

1.9

1.05

2.0

1.1

1.0

Carbon tetrachloride

CCl4

0.98
Ammonia

iso-Amylene
cyclo-Amylene
Argon

Benzene

NH3

1.3

6.0
6.3

Cesium

Cs

4.3

1.2

2.0

1.3

4.8

Iso-C5H10

5.9

cyclo-C5H10

5.8

2.6

Ar

1.3

1.6

C6H6

Chlorine

Cl2

0.68

1.1

Chlorobenzene

C6H5Cl

7.0

1.2

Chloroethane

C2H5Cl

4.0

0.9

Chloroform

CHCl3

4.7

5.9

4.8

5.8

4.8

5.7

Benzoic Acid

1.05

Chloromethane

CH3Cl

2.6

5.9

3.2

6.0

3.1

C6H5COOH

5.5

Br

3.8

3.6

Bromomethane

CH3Br

3.7

2.7

n-Butane

n-C4H10

4.9

Bromine

Cyanogen

Cyclohexylene

(CN)2

C6H12

4.7
Iso-Butane

iso-C4H10

4.6

Cd

2.3
3.4

Carbon dioxide

CO2

MKS 937B Operation Manual

1.42

7.9
6.4

Deuterium

D2

4.9
Cadmium

2.8

0.35
0.38

Dichlorodifluoromethane

CCl2F2

Dichloromethane

CH2Cl2

2.7
4.1
3.7

1.4

Dinitrobenzene

1.5

o-

7.8

1.5

m-

7.8

1.4

p-

7.6

117

C6H4(NO2)2

Ethane

Ethanol

Ethyl acetate
Ethyl ether

Ethylene

Ethylene oxide
Helium

C2H6

C2H5OH

2.6

Iodomethane

2.8

Isoamyl alcohol

2.5

Isobutylene

3.6

Krypton

CH3I

4.2

C5H11OH

2.9

C4H8

3.6

Kr

1.9

2.9

1.7

CH3COOC2H5

5.0

1.7

(C2H5)2O

5.1

Lithium

Li

1.9

5.1

Mercury

Hg

3.6

2.3

Methane

CH4

1.4

C2H4

2.4

1.5

2.2

1.6

2.2 to 2.5

1.4 to 1.8

(CH2)2O

2.5

1.5

He

0.18

1.5

0.15

Methanol

CH3OH

0.13

1.9

0.12

Methyl acetate

C7H16

8.6

Methyl ether

1,5-Hexadiene

1,5-C6H10

6.4

Cyclo-Hexadiene

Cy-C6H10

6.0

Naphthalene

C6H14

6.6

Neon

1-C6H12

5.9

Cy-C6H10

6.4

Nitrobenzene

H2

0.46

Nitrogen

0.38

Nitrotoluene (o-,m-,p-)

0.41

Nitric oxide

Heptane

Hexane
1-Hexane
Cyclo-hexane
Hydrogen

1.8

CH3COOCH3

4.0

(CH3)2O

3.0
3.0

C10H8

9.7

Ne

0.30
0.31

C6H5NO2

7.2

N2

1.0

C6H4CH3NO2

8.5

NO

1.3

0.45

1.2

0.44

1.0

Hydrogen Bromide

HBr

2.0

Hydrogen chloride

HCl

1.5

1.7

1.6

1.7

2.0

1.3 to 2.1

1.5
Hydrogen cyanide

HCN

Nitrous oxide

Oxygen

N2O

O2

1.5

1.0

1.5

1.1

1.6

0.9
0.9

Hydrogen fluoride

HF

1.4

Hydrogen iodide

HI

3.1

Hydrogen sulfide

H2S

2.2

6.0

2.2

5.7

Iodine

I2

MKS 937B Operation Manual

n-Pentane

n-C5H17

6.2

2.3

Iso-Pentane

i-C5H17

6.0

2.1

Neo-Pentane

(CH3)4C

5.7

5.4

Phenol

C6H5OH

6.2

118

Phosphine

PH3

2.6

Potassium

K

3.6

C3H8

4.2

Propane

Sulfur dioxide

SO2

2.3
Sulfur hexafluoride

SF6

3.7
3.7 to 3.9

2.1

2.3
2.8

Toluene

3.6

Trinitrobenzene
Water

C6H5CH3

6.8

C6H3(NO2)3

9.0

H2O

1.1

Propene oxide

C3H6O

3.9

n-Propene

n-C3H6

3.3

1.0

3.2 to 3.7

0.8

cyclo-Propene

cy-C3H6

3.6

Rb

4.3

2.2

AgClO4

3.6

2.4

Sodium

Na

3.0

o-Xylene

o-C6H4(CH3)2

7.8

Stannic iodide

SnI4

6.7

p-Xylene

p-C6H4(CH3)2

7.9

Rubidium
Silver perchlorate

MKS 937B Operation Manual

Xenon

119

Xe

2.87

15 Product Warranty
Extent of the Warranty
MKS Instruments, Inc., Vacuum Products Group (MKS), warrants the HPS® Products Series 937B High Vacuum, Multi-Sensor System and its
accessories to be free from defects in materials and workmanship for one (1) year from the date of shipment by MKS or authorized
representative to the original purchaser (PURCHASER). Any product or parts of the product repaired or replaced by MKS under this
warranty are warranted only for the remaining unexpired part of its one (1) year original warranty period. After expiration of the applicable
warranty period, the PURCHASER shall be charged MKS’ current prices for parts and labor, plus any transportation for any repairs or
replacement.
ALL EXPRESS AND IMPLIED WARRANTIES, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE, ARE LIMITED TO THE WARRANTY PERIOD. NO WARRANTIES, EXPRESS OR IMPLIED, WILL APPLY AFTER THIS
PERIOD.
Warranty Service
The obligations of MKS under this warranty shall be at its option: (1) to repair, replace, or adjust the product so that it meets applicable
product specifications published by MKS or (2) to refund the purchase price.
What Is Not Covered
The product is subject to above terms only if located in the country of the seller from whom the product was purchased. The above
warranties do not apply to:
I.
Damages or malfunctions due to failure to provide reasonable and necessary maintenance in accordance with MKS operating
instructions.
II.
Damages or malfunctions due to chemical or electrolytic influences or use of the product in working environments outside the
specification.
III.
Fuses and all expendable items which by their nature or limited lifetime may not function for a year. If such items fail to give
reasonable service for a reasonable period of time within the warranty period of the product; they will, at the option of MKS, be repaired or
replaced.
IV.
Defects or damages caused by modifications and repairs effected by the original PURCHASER or third parties not authorized in
the manual.
Condition of Returned Products
MKS will not accept for repair, replacement, or credit any product which is asserted to be defective by the PURCHASER, or any product for
which paid or unpaid service is desired, if the product is contaminated with potentially corrosive, reactive, harmful, or radioactive materials,
gases, or chemicals.
When products are used with toxic chemicals, or in an atmosphere that is dangerous to the health of humans, or is environmentally unsafe,
it is the responsibility of the PURCHASER to have the product cleaned by an independent agency skilled and approved in the handling and
cleaning of contaminated materials before the product will be accepted by MKS for repair and/or replacement.
In the course of implementing this policy, MKS Customer Service Personnel may inquire of the PURCHASER whether the product has been
contaminated with or exposed to potentially corrosive, reactive, harmful, or radioactive materials, gases, or chemicals when the
PURCHASER requests a return authorization. Notwithstanding such inquiries, it is the responsibility of the PURCHASER to ensure that no
products are returned to MKS which have been contaminated in the aforementioned manner.
Other Rights and Remedies
I. These remedies are exclusive. HPS SHALL NOT BE LIABLE FOR CONSEQUENTIAL DAMAGES, FOR ANTICIPATED OR LOST PROFITS,
INCIDENTAL DAMAGES OR LOSS OF TIME, OR OTHER LOSSES INCURRED BY THE PURCHASER OR BY ANY THIRD PARTY IN
CONNECTION WITH THE PRODUCT COVERED BY THIS WARRANTY, OR OTHERWISE. Some states do not allow exclusion or limitation of
incidental or consequential damage or do not allow the limitation on how long an implied warranty lasts. If such laws apply, the limitations
or exclusions expressed herein may not apply to PURCHASER.
II. Unless otherwise explicitly agreed in writing, it is understood that these are the only written warranties given by HPS. Any statements
made by any persons, including representatives of MKS, which are inconsistent or in conflict with the terms of the warranty shall not be
binding on MKS unless reduced to writing and approved by an authorized officer of MKS.
III. This warranty gives PURCHASER specific legal rights, and PURCHASER may also have other rights which vary from state to state.
IV. For MKS products sold outside of the U.S., contact your MKS representative for warranty information and service.
Warranty Performance
To obtain warranty satisfaction, contact the following: MKS Instruments, Inc., Vacuum Products Group, 5330 Sterling Drive, Boulder, CO
80301, USA, at phone number (303) 449-9861. You may be required to present proof of original purchase.

MKS 937B Operation Manual

120



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