Sierra Monitor Corporation 5100-03-IT User manual

Manual # T12020
Document Revision: D4
Model 5100-XX-IT
IT Series
Toxic Gas Sensor Module
5100-03-IT 5100-04-IT 5100-05-IT (FM Approved) 5100-06-IT 5100-08-IT
5100-10-IT 5100-12-IT 5100-21-IT 5100-25-IT 5100-26-IT 5100-88-IT
APPLICABILITY & EFFECTIVITY
Effective for all systems manufactured after May 2017.

Model 5100-XX-IT Toxic Gas Sensor Module
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©2017 Sierra Monitor Corporation. All rights reserved.
Manual Number: T12020
This manual contains intellectual property that was developed by Sierra Monitor Corporation and is
protected by the copyright laws of the United States, international copyright treaties, and all other
applicable national laws. This manual contains information regarding technology that is protected under
one or more issued or pending United States and foreign patents.
Sierra Monitor and Sentry IT are trademarks of Sierra Monitor Corporation. All other trademarks are the
property of their respective owners.
This manual is licensed to users of Sierra Monitor products and may be copied, in whole or in part.
The offices of Sierra Monitor are located at:
Sierra Monitor Corporation
1991 Tarob Court
Milpitas, CA 95035
USA
Customer Service:
Telephone: [phone]
Fax: [phone]
Toll-Free: [phone]
Email: [e-mail]
Website: www.sierramonitor.com

Model 5100-XX-IT Toxic Gas Sensor Module
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FM PERFORMANCE APPROVAL
ONLY THE FOLLOWING ITEMS, FUNCTIONS AND OPTIONS ARE FM*APPROVED
Model 5100-05-IT Hydrogen Sulfide Gas Sensor Module
Sensor Module
Model 5100-05-IT
Sensor Module - Hydrogen Sulfide
Calibration Equipment
Model 1250-01
Gas Sensor Calibration Kit, Type A
Model 1260-05
Hydrogen Sulfide in N2, 25 ppm Gas Cylinder
Model 1260-45
Hydrogen Sulfide in N2, 10 ppm Gas Cylinder
Model 5358-01
Calibration Adapter
Notes:
1) Apparatus must be installed in accordance with National Electrical Code.
2) FM Comments
*FM Approvals, a subsidiary of FM Global
Project# 3034435

Model 5100-XX-IT Toxic Gas Sensor Module
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TABLE OF CONTENTS
Product Description...................................................................................................................... 7
1.1 General.........................................................................................................................................................7
1.2 Product Configuration ..................................................................................................................................8
1.3 Theory of Operation .....................................................................................................................................8
1.4 Modes of Operation......................................................................................................................................8
1.4.1 Sentry Interface.....................................................................................................................................8
1.4.2 Modbus Operation ................................................................................................................................8
1.4.3 Analog Operation..................................................................................................................................8
1.4.4 Remote Sensor.....................................................................................................................................8
1.4.5 HART Connection.................................................................................................................................9
1.4.6 Remote Alarm Reset.............................................................................................................................9
1.4.7 Optional Integral Relays........................................................................................................................9
1.5 Mechanical...................................................................................................................................................9
1.5.1 Enclosure..............................................................................................................................................9
1.5.2 Transmitter Electronics.......................................................................................................................11
1.5.3 Sensor Assembly................................................................................................................................11
1.6 Interconnect Wiring ....................................................................................................................................11
1.7 Power Requirements..................................................................................................................................11
Cautions & Warnings.................................................................................................................. 12
2.1 Introduction.................................................................................................................................................12
2.2 Gas Sensor Modules –General.................................................................................................................12
2.3 Wiring Warnings.........................................................................................................................................12
2.4 Calibration Frequency................................................................................................................................12
Quick Start................................................................................................................................... 13
3.1 Overview ....................................................................................................................................................13
3.2 Wiring.........................................................................................................................................................13
3.3 Module Installation .....................................................................................................................................13
3.4 Transmitter Installation...............................................................................................................................13
3.5 Startup and Operation................................................................................................................................14
3.6Zero Stabilization .......................................................................................................................................14
Installation................................................................................................................................... 15
4.1 Sensor Module Locations...........................................................................................................................15
4.2 Wiring.........................................................................................................................................................16
4.2.1 Analog 4-20 mA Operation .................................................................................................................16
4.2.2 Modbus Operation Using RS-485 Connection....................................................................................16
4.2.2.1 Termination Resistor Jumpers.................................................................................................... 16
4.2.2.2 Bias Jumpers (BIAS A, BIAS B) ................................................................................................. 16
4.2.3 Sentry Operation Using Sentry Connection........................................................................................16
4.2.4 General ...............................................................................................................................................17
4.3 Enclosure Installation.................................................................................................................................17
4.4Transmitter and Sensor Installation ...........................................................................................................18
4.5 Module Address Switch..............................................................................................................................19
Operation..................................................................................................................................... 25
5.1 Introduction.................................................................................................................................................25
5.2 Data Entry Keypad.....................................................................................................................................25
5.3 Main Menu..................................................................................................................................................26
5.4 Set-Up........................................................................................................................................................27
5.5 Maintenance Sub-Menu.............................................................................................................................29
Calibration ................................................................................................................................... 30
6.1 Calibration Frequency................................................................................................................................30
6.2 Calibration Preparation ..............................................................................................................................30
6.3 Calibration Gas Delivery Methods..............................................................................................................30

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6.4 Sensor Exposure to Gas............................................................................................................................31
6.5 Calibration Sub-Menu ................................................................................................................................32
6.5.1 5100-03-IT Oxygen Deficiency ...........................................................................................................33
6.5.2 5100-88-IT Carbon Dioxide.................................................................................................................33
Appendix A. Service.......................................................................................................................... 34
Appendix A.1. Sensor Module Configuration........................................................................................................34
Appendix A.2. Enclosure Replacement ................................................................................................................34
Appendix A.3. Transmitter Replacement..............................................................................................................35
Appendix A.4. Sensor Replacement.....................................................................................................................35
Appendix A.5. Installation Inspection....................................................................................................................36
Appendix A.5.1. Controller Installation..............................................................................................................36
Appendix A.5.2. Cabling Installation .................................................................................................................36
Appendix A.5.3. Sensor Module Installation .....................................................................................................36
Appendix A.5.4. Moisture Traps and Rainshields.............................................................................................36
Appendix A.5.5. Standard Voltages ..................................................................................................................36
Appendix A.6. Inspection and Troubleshooting Guide..........................................................................................36
Appendix A.6.1. Ir Module Does Not Respond to Gas......................................................................................36
Appendix A.6.2. Module Displays “Starting” for more than 1 Hour ...................................................................36
Appendix A.6.3. Module Does Not Display the Correct %PPM........................................................................37
Appendix A.6.4. Display Shows ‘F’ – Sensor Missing or Bad Sensor ..............................................................37
Appendix A.6.5. Module Shows “***Calibration Required***” ...........................................................................37
Appendix A.6.6. Display Shows “H” or “L”.........................................................................................................37
Appendix A.6.7. Display Shows “M” – Not Calibrated.......................................................................................37
Appendix A.6.8. Display Shows “C” – Calibration Mode...................................................................................37
Appendix A.6.9. Display Shows “S” – Sentry Connection.................................................................................37
Appendix A.6.10. Diagnostic LEDs ...................................................................................................................37
Appendix B. Specifications............................................................................................................... 38
Appendix C. Model Numbers and Parts List.................................................................................... 41
Appendix D. Limited 2 Year Warranty .............................................................................................. 42
Appendix E. Remote Sensor Drawing.............................................................................................. 43
Appendix F. Modbus Memory Map................................................................................................... 44
Appendix G. HART............................................................................................................................. 45
Appendix H. Gas Sensor Module Calibration .................................................................................. 52
Appendix H.1. Calibration for 5100-25-IT .............................................................................................................52
Appendix H.2. Calibration for 5100-26-IT .............................................................................................................56
Appendix I. 5100-88-IT Dimensions.................................................................................................. 57
Appendix J. 5100-05-IT FM Performance Approval......................................................................... 58
Appendix K. 5100-XX-IT SIL-2 Certificates....................................................................................... 60
Appendix L. 5100-05-IT ATEX Certificate......................................................................................... 60

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LIST OF FIGURES
Figure 1: Model 5100-XX-IT Toxic Gas Sensor Module –Mounting Options............................................................9
Figure 2: Model 5100-05-IT-S1/S2 Toxic Gas Sensor –Stainless Steel Enclosure, Dimensions.......................... 10
Figure 3: Model 5100-05-IT-A1/A2 Toxic Gas Sensor –Cast Aluminum Enclosure, Dimensions ......................... 10
Figure 4: Specific Gravities...................................................................................................................................... 15
Figure 5: Typical Mounting Options......................................................................................................................... 15
Figure 6: Minimum Wire Gauges............................................................................................................................. 17
Figure 7: Sensor Module Address Switch Positions................................................................................................ 19
Figure 8: Transmitter Face Plate............................................................................................................................. 19
Figure 9: Interface Board Connectors ..................................................................................................................... 20
Figure 10: RS-485 –Termination, BIAS Jumper..................................................................................................... 20
Figure 11: mA Circuit Types.................................................................................................................................... 21
Figure 12: 4-20 mA Circuit Type Connections for 5100-XX-IT................................................................................ 22
Figure 13: Wiring Connections for Modbus and Sentry Interface ........................................................................... 23
Figure 14: Wiring Connections for Remote Alarm Reset ........................................................................................ 24
Figure 15: Face Plate with Operator Keypad .......................................................................................................... 25
Figure 16: Master Menu .......................................................................................................................................... 26
Figure 17: Operation Display Values....................................................................................................................... 26
Figure 18: Set-Up Configuration Part 1................................................................................................................... 28
Figure 19: Set-Up Configuration Part 2................................................................................................................... 29
Figure 20: Maintenance Menu................................................................................................................................. 29
Figure 21: Model 5358-01 Calibration Adapter ....................................................................................................... 30
Figure 22: Calibration Sub-Menu............................................................................................................................. 32
Figure 23: Module Components .............................................................................................................................. 34
Figure 24: Remote Sensor Drawing........................................................................................................................ 43
Figure 25: Wiring Connections Table...................................................................................................................... 45
Figure 26: 4-20 mA Circuits Types 5100-XX-IT –Connections - HART ................................................................. 46
Figure 27: Electrolyte Replacement ........................................................................................................................ 52
Figure 28: Sensor Assembly –Exploded View ....................................................................................................... 54
Figure 29: Model 5100-25-IT-A1/A2 and Model 5100-26-IT-A1/A2........................................................................ 55
Figure 30: Model 5100-25-IT-S1 and Model 5100-26-IT-S1................................................................................... 55
Figure 31: Model 5100-88-IT-A1 Dimensions ......................................................................................................... 57

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PRODUCT DESCRIPTION
1.1 General
The Model 5100-XX-IT Toxic Gas Sensor Module is a smart transmitter and member of the IT Series family and it
offers a broad array of features including:
•Integral alphanumeric LED display
•Up to 180 day calibration frequency
•FM Approval for performance and safety
•SIL-2 Certified
•Optional integral alarm relays (3)
•4-20 mA output
•Modbus®RTU interface
1
•SMC Sentry interface
•Optional HART interface
•316 Stainless steel enclosure option
•Remote sensor option
•Low maintenance and operation costs
•ATEX Approval (5100-05-IT)
The 5100-XX-IT is designed and approved for installation and operation in hazardous locations. Members of the
5100-XX-IT Series Toxic Gas family include:
•5100-03-IT Oxygen Gas Sensor Module
•5100-04-IT Carbon Monoxide Gas Sensor Module
•5100-05-IT Hydrogen Sulfide Gas Sensor Module
•5100-06-IT Chlorine Gas Sensor Module
•5100-08-IT Chlorine Dioxide Gas Sensor Module
•5100-10-IT Sulfur Dioxide Gas Sensor Module
•5100-12-IT Nitrogen Dioxide Gas Sensor Module
•5100-21-IT Hydrogen Chloride Gas Sensor Module
•5100-25-IT Ammonia Gas Sensor Module
•5100-26-IT Hydrogen Fluoride Gas Sensor Module
•5100-88-IT Carbon Dioxide Gas Sensor Module
1
®Registered trademark of Schneider Electric

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1.2 Product Configuration
Various module mounting configurations can be implemented without special fixtures. Where applicable, these
options are factory configured prior to shipment. Mounting configuration can be selected by the installer or field
technician and are fully described in this manual. Sensor must always be oriented downward.
1.3 Theory of Operation
Electrochemical sensors are fuel cell-like devices consisting of an anode, cathode, and electrolyte. The
components of the cell are selected so a subject gas, allowed to diffuse into the cell, will cause a chemical
reaction and generate a current. The cells are diffusion limited so the rate the gas enters the cell is solely
dependent on the gas concentration. The current generated is proportional to the rate of consumption of the
subject gas in the cell.
Sierra Monitor electrochemical sensors provide improved reliability by allowing the gas to diffuse into the sensor
through a capillary port, rather than diffusing through membranes. The result is an extremely stable sensor with
very low temperature and pressure coefficients and the capability to monitor gas as ppm.
1.4 Modes of Operation
1.4.1 Sentry Interface
IT gas sensor modules can be installed on Sierra Monitor Sentry Model 5000 controllers Ver. 6.XX MFD after
9/1/95. When it is installed in a Sentry system the IT module must have a unique address which can be
established by setting an address between 1 and 8 on the Module Address Switch accessible from the cover plate
as illustrated in Figure 8. Figure 13 in this manual provides the wiring terminations for connections to the Sentry
controller.
NOTE: The Model # 5100-88-IT CO2 gas sensor module range is 0-5000 ppm. Therefore, the Sentry
Controller must be configured for a 0-100 % full scale input. The Sentry cannot display
engineering units up to 5000. The alarm set points need to be set as a percentage of full scale. For
example, a 2500 ppm alarm set point is equal to 50% scale.
When the module is operated in conjunction with a Sentry controller, the alarm relay set-up (Section 5.3) should
be set to “Sentry”, allowing the Sentry controller to manage alarm relay action rather than the 5100-XX-IT Gas
Sensor Module.
1.4.2 Modbus Operation
An RS-485 Modbus RTU serial interface allows direct connection to standard PLCs and DCSs. The Module
Address Switch (Section 4.5) allows the user to select up to 15 different Modbus addresses. Also, an additional
254 Modbus addresses are available via menu selection. Figure 13 in this manual provides the wiring
terminations for Modbus connections. The 5100-XX-IT provides the wiring terminations for Modbus connections.
1.4.3 Analog Operation
The analog 4-20 mA interface allows direct connection to standard controller and distributed system. The module
is an active current source.
The standard configuration is set up for a 3-wire non-isolated connection. An optional 4-wire isolated connection
is also available and can be enabled by changing JP1 and JP2. (Figure 12)
1.4.4 Remote Sensor
The Remote Sensor option can be used to remotely mount some sensors up to 15’ from the transmitter. Refer to
Appendix E for allowable distances.

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1.4.5 HART Connection
A HART interface option is available. Refer to Appendix G for information.
1.4.6 Remote Alarm Reset
An input is available for connection of remote alarm reset. Figure 14 provides the wiring termination for
connecting the remote alarm reset. This only resets local alarms, not Sentry alarms.
1.4.7 Optional Integral Relays
The optional relays are integral to the gas sensor module and are rated as SPDT, 250V AC, 5 Amps* for the High
Alarm and Low Alarm relays and SPDT, 250V AC, 0.25 Amp for the Trouble relay.
* HART option alarm relays are all SPDT, 250V AC, 2 Amp
If the gas sensor module is provided with the optional relays, it will include Terminal P4 on the interface board
(Figure 9 and Figure 10). Relay output connections are on P4.
1.5 Mechanical
The sensor module is comprised of the following three primary components:
1.5.1 Enclosure
Standard on the 5100-XX-IT is an explosion-proof, rain-tight cast aluminum electrical housing (Figure 3) with
three ¾” FNPT conduit hubs. The 5100-XX-IT-S has a 316 Stainless Steel enclosure (Figure 2). Both enclosure
covers have a viewing window. The design of the enclosure allows 3-way mounting choices as shown in
Figure 1.
NOTE: Module installation must be such that it is mounted vertically with sensor pointing downward.
Figure 1: Model 5100-XX-IT Toxic Gas Sensor Module –Mounting Options

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NOTE: Figure 2 and Figure 3 are valid for all except 5100-25/26-IT. See Appendix H.
Figure 2: Model 5100-05-IT-S1/S2 Toxic Gas Sensor –Stainless Steel Enclosure, Dimensions
Figure 3: Model 5100-05-IT-A1/A2 Toxic Gas Sensor –Cast Aluminum Enclosure, Dimensions

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1.5.2 Transmitter Electronics
Electronic Assembly consisting of one printed circuit board assembly mounted under a cover plate, plugged into
one field termination board. Connectors for wiring for power, signal interface and alarm relays are located on the
bottom of the termination board.
1.5.3 Sensor Assembly
The sensor assembly includes an explosion proof housing containing the gas sensor and a wiring harness for
connection to the transmitter. The sensor assembly threads into one hub of the enclosure. The exposed end of
the sensor assembly is threaded to allow connection of a rain-shield or calibration gas.
1.6 Interconnect Wiring
Not supplied with the sensor module, but necessary to the installation and operation is the shield cable which
connects the module to its power source and controller. Before this wiring is installed it is important to read and
understand the control system installation instructions to determine wiring requirements and alternatives.
1.7 Power Requirements
The modules operate on 24V DC power between 10V DC and 30V DC. Filtered, regulated DC power must be
supplied from a separate source or from an approved Sentry or IT controller.

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CAUTIONS & WARNINGS
2.1 Introduction
Although the IT Transmitter Modules are designed and constructed for installation and operation in industrial
applications including “hostile” environments, caution should be taken to insure that the installation is made in
compliance with this instruction manual and that certain procedures and conditions are avoided. This chapter
discusses the necessary cautions. Read the entire chapter prior to installation of the equipment.
2.2 Gas Sensor Modules –General
Avoid installing sensor modules where they will be unnecessarily exposed to wind, dust, water (i.e. direct hose
down), shock, or vibration. Observe temperature range limitations.
Sensors may be adversely affected by prolonged exposure to certain materials. Loss of sensitivity, or corrosion,
may be gradual if such materials are present in low concentrations. These materials include: Halides (compounds
containing chlorine, fluorine, bromine, iodine), acid vapors, caustic liquids or mists.
Care has been taken by the manufacturer to ship modules in protective packaging to avoid contamination prior to
installation. It is recommended that the modules remain protected during installation and that the covering be
removed immediately prior to system start-up.
During normal use the O2, CO, H2S, and SO2sensors are protected from dirt and oil contamination by a sintered
metal cover. If this cover becomes clogged, the response of the sensor will be reduced. Protect the sensor from
contamination by careful placement, or by use of rain shields and dust shields.
Sensor modules must not be painted. Paint may contain compounds which will contaminate the sensor. Paint will
cause clogging of the sintered metal cover and will cause difficulties during attachment of the calibration head or
other maintenance activity. It is recommended that the module be tagged "DO NOT PAINT".
2.3 Wiring Warnings
The manufacturer recommends that extra caution be taken where the installation is near any sources of
electromagnetic or radio frequency interference. Precautions include:
•Avoid running sensor module cable close to high power cables, radio transmission lines, or cables subject
to pulses of high current.
•Avoid running cables near large electric motors or generators.
•When the sensor module is to be operated in analog (4-20mA output) mode shielded cable is required.
•When shielding is used, it is recommended that shields be grounded at the controller and nowhere else.
•All splices must be via either a termination hardware system or soldered. Improperly spliced cable can
result in corrosion, resistance changes and system errors. The use of wire nuts and crimp-on connectors
is unacceptable.
NOTE: Installation and wiring must be in accordance with the National Electrical Code. Voltage AC
conductors are not to be run in the same conduit as voltage DC conductors.
2.4 Calibration Frequency
The H2S calibration frequency is six months or 180 days. However, prudent gas detector maintenance practices
normally suggest a simple recalibration following incidences of exposure to high levels of gas that would lead to
alarm activation within any system utilizing the output of the gas sensor module.

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QUICK START
3.1 Overview
The gas sensor module has been supplied factory calibrated and ready for immediate installation and operation.
An installer familiar with installation and operation of gas detection products can use this section to begin
immediate use of the module.
3.2 Wiring
See Section 4.2 to determine if 3-wire or 4-wire operation is necessary.
Provide two conductor twisted shielded wiring from the power supply/control device to the sensor module location.
Use wire that is 18 AWG or larger.
3.3 Module Installation
The sensor can be mounted in a variety of configurations supported by the conduit. See Figure 3 to determine
which configuration is best for your specific application. The default configuration enables the modules to be put in
line with other modules with the sensor element below the transmitter. To change the configuration simply remove
the transmitter and rotate to the appropriate configuration and remount the standoffs and transmitter.
The module is designed to be installed on a ¾” NPT or M20 conduit. During installation heed the following:
•The installation must meet any hazardous environment codes for electrical equipment.
•The sensor module enclosure mounting must be spaced far enough from any vertical surface to allow
removal and replacement of the sensor assembly which is threaded into one ¾” conduit entry.
•Sensor housing must be oriented vertically pointing downward.
•If module is installed outdoors it is recommended that it be sheltered from direct sunlight.
3.4 Transmitter Installation
To install the transmitter printed circuit assembly into the housing, carefully turn the faceplate so that the printing
is in the correct horizontal position for the mounting configuration and slide the assembly over the two stand-offs
in the enclosure.
Hand tighten the two captive panel thumb screws into the stand-offs. Replace the enclosure cover prior to
providing power to the transmitter.
NOTE: If the transmitter is installed in a classified hazardous area, replace the threaded cover prior to
providing power.

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3.5 Startup and Operation
To begin operation of the sensor module, activate the instrument loop with 10-30V DC. Each time the sensor
module is powered up it will perform a warm-up for approximately 1.0 minutes (60 seconds). During this time the
display will read “Starting”. The loop output will be held at 4 mA.
NOTE: If the sensor is uncalibrated, the startup display will state “UNCALIB” instead of “STARTING”.
NOTE: The 5100-06-IT, 5100-08-IT, 5100-25-IT, 5100-26-IT and 5100-88-IT require 300 seconds warm-up
period. After the warm-up period has expired, the display will indicate the gas concentration. Also,
the instrument loop will be released to output current in the range of 4 to 20 mA. The actual
current is linear with the gas concentration and depends on the selected range. For instance,
when the range of 0 to 50 PPM has been selected, a current of 4 mA corresponds to 0 PPM and a
current of 20 mA corresponds to 50 PPM.
3.6 Zero Stabilization
All electrochemical sensors require at least 30 minutes on power prior to calibration. This allows the electrode
potentials to equilibrate, resulting in a stable zero signal level.

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INSTALLATION
4.1 Sensor Module Locations
NOTE: All IT modules are factory pre-configured and calibrated. All modules are tagged to indicate the
configuration including the sensor module number Identify all components during unpacking and
install using the factory configuration.
The gas sensor module utilizes a diffusion type sensor which should be
located close to either the expected source or destination of the gas
hazard. If the gas is heavier than air, the sensor module should be installed
within 24 inches of the ground or floor. If it is lighter than air, move it above
6’.
After optimum locations are determined based on the above
recommendations, consideration should be given to placing the sensor
modules in locations which are accessible for calibration service. Slight
adjustments to the location of the sensor module may have little impact on
effectiveness but major effect on accessibility.
•Modules should be placed close to the potential source of gas.
•Modules should be placed in areas accessible for calibration.
•Sensors should be pointed down and the conduit should include an
inverse trap to reduce moisture (condensation) from accumulating in
the electronics enclosure.
•Remote calibration fitting (5360-00) should be used to facilitate calibration gas delivery. Run polyurethane
tubing (1/4” O.D. x 1/8” I.D.) from fitting to an accessible location.
Model
Gas
Gas Density
N/A
Air
1.00
5100-04-IT
CO
0.97
5100-05-IT
H2S
1.19
5100-06-IT
Cl2
2.49
5100-08-IT
ClO2
3.09
5100-10-IT
SO2
2.26
5100-12-IT
NO2
2.12
5100-21-IT
HCl
1.27
5100-25-IT
NH3
0.60
5100-26-IT
HF
1.86
5100-88-IT
CO2
1.53
Figure 4: Specific Gravities
Figure 5: Typical Mounting Options

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4.2 Wiring
4.2.1 Analog 4-20 mA Operation
For a 3-wire non-isolated connection, set jumpers, located on the bottom of the transmitter board, to the lower
position as illustrated in Figure 12. Verify that both jumpers are in the position marked by 3-wire. When using a
3-wire connection, a minimum of an 18 AWG, 3-conductor shielded cable must be used. A cable shield must
never be used as a conductor. Larger gauge wire is recommended with distances over 1000’. Connect wires as
shown in Figure 10.
For a 4-wire isolated connection, set jumpers, located on the bottom of the transmitter board, to the upper position
as illustrated in Figure 10. Verify that both jumpers are in the position marked by 4-wire. When using a 4-wire
connection, a minimum of 2 each of an 18 AWG, 2 conductor twisted/shielded pair cable must be used. A cable
shield must never be used as a conductor. Larger gauge wire is recommended with distances over 1000’.
Connect wires as shown in Figure 10.
4.2.2 Modbus Operation Using RS-485 Connection
Use a minimum of 18 AWG, 2-conductor for DC power connection. No shield required. In addition, use a
minimum of 24 AWG, low capacitance, shielded data cable for RS485 half-duplex communication. The installation
may be planned in a manner which provides up to 32 sensor modules on a single home run.
Standard default RS485 Settings are: 38,400 baud, 8 bits, 1 stop bit, no parity
4.2.2.1 Termination Resistor Jumpers
Termination resistors are used in RS-485 wire runs to provide impedance matching. The IT series modules use a
120 Ohm resistor for this function. The cable being used for this RS-485 connection must have a minimum of 100
Ohm impedance with a maximum of 120 Ohms.
Installations where the cable length is under 100’, termination resistors may not be required. In installations where
the cable length is greater than 100’, it is recommended to place the termination jumpers on the first device and
last device on the RS-485 wire run. Termination jumpers must be removed from all other modules connected
between the first and last device. The first device in the RS-485 multiplexed bus is usually a gas controller or
PLC. Factory term resistor setting is “not enabled.”
4.2.2.2 Bias Jumpers (BIAS A, BIAS B)
Bias resistors are used to force RS-485 receiver outputs to a known (fail-safe) state, when the bus is idle. Bias
jumpers are always installed in pairs as the bias must be placed on both the TX A and TX B lines. Sierra Monitor’s
IT series of toxic gas sensors automatically apply the bias jumpers, and are factory installed so that the bias is
always enabled.
4.2.3 Sentry Operation Using Sentry Connection
See Figure 13. Use a minimum of 18 AWG, 3-conductor cable up to 2000’. The cable may or may not be
shielded. We recommend shielded cable in circumstances that there could be RF or EM interference present.
Shield to be terminated and grounded only at the Sentry controller. Shield must be cut and dressed at the module
end so that no part of it comes in contact with the conduit or ground.
NOTE: Be sure to follow all local electric code and safety requirements when installing the 5100-XX-IT
Gas Sensor Module.

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4.2.4 General
Install conduit as required by local code or construction specifications. Provide for splice boxes where multiple
modules will be wired to a single run. Pull conductors of the correct gauge wire from the controller to each splice
box and from the respective splice box to each planned module location. See for proper wire termination in the
splice box. Twisted wire secured with wire nuts is not an acceptable splice.
NOTE: The drain wire of shielded cable must NOT be used as one of the conductors. Installation and
wiring must be in accordance with the National Electrical Code. Temperature rating of cable wire
must be at least 75°C. If cable runs through higher temperature environments, it must be specified
for that environment.
4.3 Enclosure Installation
To protect the transmitter and sensor assembly they should be removed from the enclosure and preserved until
final installation and wiring termination.
Number
of
Modules
Maximum Length of Wire Run (feet)
500
1,000
2,000
3,000
5,000
1
18
18
16
16
14
2
18
18
14
12
xx
3
18
16
12
xx
xx
4
16
14
12
xx
xx
Figure 6: Minimum Wire Gauges
Prior to installation and wiring complete the following steps.
1. Remove the transmitter from the module housing by:
a) Unscrew the two captive panel screws on the faceplate.
b) Lift the transmitter out of the enclosure.
c) Unplug the sensor cable from transmitter connector P2.
d) Remove the sensor assembly from the enclosure hub.
2. Install the module enclosure onto the end of the supply conduit and/or bolt into position as required.
NOTE: When enclosure earth grounding is required for the installation a grounding lug is located in the
base of the enclosure. Install the earth ground under the green ground screw.

Model 5100-XX-IT Toxic Gas Sensor Module
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4.4 Transmitter and Sensor Installation
When all pre-wire is complete:
1. Install sensor assembly in the open hub on the module enclosure. The sensor assembly thread must be fully
seated into the hub and tightened to maintain explosion proof assembly.
2. Connect the wires which return to the controller to interface board connectors P1, P2, P3 and P4 according to
Figure 9 and as detailed in the connector tables below.
3. Connect the sensor assembly cable to top transmitter board connector P2.
4. Align the headers between the top transmitter board and the lower interface board then push together.
5. Turn the rotary switch to correct sensor address if required.
6. Carefully return the transmitter to the enclosure, installing it over the two stand-off’s. Tighten the retaining
screws into the stand-offs.
7. Cycle power to accept module address change.
8. Establish the module address according to Section 4.5.
NOTE: The starting delay period normally takes approximately 3 minutes but under some circumstances
can take longer. For optimum performance, it is recommended that a calibration be performed
after 24 hours of operation.
P1
PCB Label
Function
1
Switch
IN +
Digital Input SW +
2
IN -
Digital Input SW -
3
4-20
IN +
4-20 mA Input +
4
IN -
4-20 mA Input -
5
GND
Ground
6
4-20
OUT +
4-20 mA Output +
7
OUT -
4-20 mA Output -
P2
1
RS 485
+
RS 485 (+) (A)
2
-
RS 485 (-) (B)
3
S
RS 485 shield (Isolated GND)
4
+
RS 485 (+) (A)
5
-
RS 485 (-) (B)
6
S
RS 485 shield (Isolated GND)
P3B
1
P
V DC Power
2
S
Sentry Signal or
Communication
3
G
V DC Ground
P3A
4
P
V DC Power
5
S
Sentry Signal or
Communication
6
G
V DC Ground
P4*
PCB Label
Function
1
WARNING
N/C
Low Alarm Relay NC
2
COM
Low Alarm Relay COM
3
N/O
Low Alarm Relay NO
4
ALARM
N/C
High Alarm Relay NC
5
COM
High Alarm Relay COM
6
N/O
High Alarm Relay NO
7
TRBL**
N/C
Trouble Alarm Relay NC
8
COM
Trouble Alarm Relay COM
9
N/O
Trouble Alarm Relay NO
*P4 Connections are installed only when the optional
Relays are included
** Trouble relay is a fail-safe so it is energized for normal
operation, functions are labeled for normal operation.

Model 5100-XX-IT Toxic Gas Sensor Module
Page 19 of 62
4.5 Module Address Switch
For digital interface applications the module address switch (or Modbus node) Figure 8 must be set per the table
below.
Position
Address
Position
Address
1
Sensor 1
9
Sensor 09
2
Sensor 2
A
Sensor 10
3
Sensor 3
B
Sensor 11
4
Sensor 4
C
Sensor 12
5
Sensor 5
D
Sensor 13
6
Sensor 6
E
Sensor 14
7
Sensor 7
F
Sensor 15
8
Sensor 8
0
Software Menu
Figure 7: Sensor Module Address Switch Positions
NOTE: For Sentry (PSG) applications only sensor addresses 1-8 are allowed. If using Modbus output
sensor addresses 1-15 are available. Position 0 allows the Modbus Address to be set by software
menu, in the range 16-254.
Figure 8: Transmitter Face Plate

Model 5100-XX-IT Toxic Gas Sensor Module
Page 20 of 62
Figure 9: Interface Board Connectors
Figure 10: RS-485 –Termination, BIAS Jumper