RKI Instruments M2 User manual

RKI Instruments, Inc.
www.rkiinstruments.com
M2 Transmitter
Operator’s Manual
Part Number: 71-0107RK
Revision: D
Released: 10/7/10

M2 Transmitter Operator’s Manual
WARNING
Read and understand this instruction manual before
operating instrument. Improper use of the gas monitor
could result in bodily harm or death.
Periodic calibration and maintenance of the gas
monitor is essential for proper operation and correct
readings. Please calibrate and maintain this instrument
regularly! Frequency of calibration depends upon the
type of use you have and the sensor types. Typical
calibration frequencies for most applications are
between 3 and 6 months, but can be required more
often or less often based on your usage.

M2 Transmitter Operator’s Manual
Product Warranty
RKI Instruments, Inc. warrants gas alarm equipment sold by us to be free from defects in
materials, workmanship, and performance for a period of one year from date of shipment
from RKI Instruments, Inc. Any parts found defective within that period will be repaired
or replaced, at our option, free of charge. This warranty does not apply to those items
which by their nature are subject to deterioration or consumption in normal service, and
which must be cleaned, repaired, or replaced on a routine basis. Examples of such items
are:
Warranty is voided by abuse including mechanical damage, alteration, rough handling, or
repair procedures not in accordance with the operator’s manual. This warranty indicates
the full extent of our liability, and we are not responsible for removal or replacement costs,
local repair costs, transportation costs, or contingent expenses incurred without our prior
approval.
THIS WARRANTY IS EXPRESSLY IN LIEU OF ANY AND ALL OTHER
WARRANTIES AND REPRESENTATIONS, EXPRESSED OR IMPLIED,
AND ALL OTHER OBLIGATIONS OR LIABILITIES ON THE PART OF
RKI INSTRUMENTS, INC. INCLUDING BUT NOT LIMITED TO, THE
WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. IN NO EVENT SHALL RKI INSTRUMENTS,
INC. BE LIABLE FOR INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
LOSS OR DAMAGE OF ANY KIND CONNECTED WITH THE USE OF
ITS PRODUCTS OR FAILURE OF ITS PRODUCTS TO FUNCTION OR
OPERATE PROPERLY.
This warranty covers instruments and parts sold to users by authorized distributors,
dealers, and representatives as appointed by RKI Instruments, Inc.
We do not assume indemnification for any accident or damage caused by the operation of
this gas monitor, and our warranty is limited to the replacement of parts or our complete
goods.
a) Absorbent cartridges d) Batteries
b) Pump diaphragms and valves e) Filter elements
c) Fuses

M2 Transmitter Operator’s Manual
Table of Contents
Chapter 1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
About the M2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
About this Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Chapter 2: Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
External Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Internal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Chapter 3: Installation & Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Mounting the M2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Wiring the M2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Chapter 4: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Information Screen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4 - 20 mA Signal Output Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Alarm Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Chapter 5: Configuration Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Viewing & Changing M2 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Chapter 6: Gas Type Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Selecting the Gas Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

M2 Transmitter Operator’s Manual
Chapter 7: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Calibration Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Calibration, Combustible Gas, CO2, and Toxic Versions . . . . . . . . . . . . . . . . . . . . . 40
Calibration, Oxygen Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Replacing Components of the M2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Chapter 8: RS-485 Modbus Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Wiring the M2 in a Modbus System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Using the M2 in a 4-wire Modbus System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Modbus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Supported Modbus Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Appendix A: Control Button Quick Reference Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Appendix B: Function Code 16 Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
(Appendix B available from RKI Instruments, Inc. Not included in manual as normally
provided with M2 detector head.)

1 M2 Transmitter Operator’s Manual
Chapter 1: Introduction
Overview
This chapter briefly describes the M2 Transmitter. This chapter also describes the M2
Transmitter Operator’s Manual (this document). Table 1 at the end of this chapter lists the
specifications for the M2.
About the M2 Transmitter
The M2 transmitter is a fixed mount, continuous-monitoring detector head. All user
adjustable parameters may be accessed using push button switches. In addition,
calibration may be performed non-intrusively by use of a magnetic wand accessory which
activates magnetic switches through a window at the front face of the detector head.
The M2 displays the current gas reading on an LCD display which is visible through the
window in the cover (front face) and provides a 4 - 20 mA signal which indicates the
target gas reading for use by a gas monitoring controller, recording device, or
programmable controller. The M2 also provides an RS-485 Modbus output. Three sets of
relay contacts, two controlled by the gas alarms and one by the fail alarm, rated at 115
VAC 5 amps are available for controlling devices such as lights or horns or for controlling
higher rated relays.
Four operating modes allow you to display and change setup and calibration settings and
change the gas type. They are Calibration Mode, Configuration Mode, Gas Type Mode,
and Modbus Mode.
About this Manual
The M2 Transmitter Operator’s Manual uses the following conventions for notes, cautions,
and warnings.
NOTE: Describes additional or critical information.
CAUTION: Describes potential damage to equipment.
WARNING: Describes potential danger that can result in injury or death.

M2 Transmitter Operator’s Manual 2
Specifications
Table 1 lists specifications for the M2.
Table 1: M2 Specifications
Target Gas/Detection
Range Combustible Gas/Carbon Dioxide (CO2)
• Catalytic LEL: 0 - 100% LEL, 1% LEL increments (CH4calibration
unless otherwise specified. H2specific detector available)
•IR(infrared)CH
4LEL: 0 - 100% LEL, 1% LEL increments
• IR HC LEL: 0 - 100% LEL, 1% LEL increments (propane calibration)
•IRCH
4Volume: 0 - 100 % volume, 1% increments
•IRCO
2ppm: 0 - 5,000 ppm, 20 ppm increments
•IRCO
2Volume: 0 - 5.00 % volume, 0.01% increments
•IRCO
2Volume: 0 - 50.0 % volume, 0.1% increments
•IRCO
2Volume: 0 - 100 % volume, 1% increments
Oxygen
•Oxygen(O
2): 0 - 25.0 % volume, 0.1% increments
CO/H2S
• Carbon Monoxide (CO): 0 - 300 ppm, 1 ppm increments
• Hydrogen Sulfide (H2S): 0 - 100 ppm, 1 ppm increments
ESM-01 Toxic
•Ammonia(NH
3): 0 - 75.0 ppm, 0.1 ppm increments
•Arsine(AsH
3): 0 - 1.50 ppm, 0.01 ppm increments
•Chlorine(Cl
2): 0 - 3.00 ppm, 0.01 ppm increments
• Hydrogen Cyanide (HCN): 0 - 15.0 ppm, 0.1 ppm increments
• Phosphine (PH3): 0 - 1.00 ppm, 0.01 ppm increments
• Sulphur Dioxide (SO2): 0 - 6.00 ppm, 0.01 ppm increments
Alarm Settings
(Alarm 1/Alarm 2) Combustible Gas (%LEL): 10 %LEL/50 %LEL Combustible Gas (%Volume): 100 %/100 %
CO2 0 - 5,000 ppm: 2,500 ppm/5,000 ppm
CO2 0 - 5.00%: 0.50 %/3.00 %
CO2 0 - 50.0%: 50.0%/50.0%
CO2 0 - 100%: 100%/100%
Oxygen: 19.5%(decreasing)/23.5%(increasing)
Carbon Monoxide: 25 ppm/50 ppm
Hydrogen Sulfide: 10 ppm/50 ppm
Ammonia: 12 ppm/25 ppm
Arsine: 0.20 ppm/0.50ppm
Chlorine: 0.50 ppm/1.50 ppm
Hydrogen Cyanide: 5.0 ppm/10.0 ppm
Phosphine: 0.10 ppm/0.30 ppm
Sulphur Dioxide: 1.00 ppm/2.00 ppm
Construction
(housing) Explosion-proof Junction Box, NEMA 4
Area Classification Explosion-proof for Class I, Groups B, C, and D (Combustible, CO2, CSA
Type CO and H2S, and CSA Type oxygen)

3 M2 Transmitter Operator’s Manual
WARNING: When using the M2, you must follow the instructions and warnings in
this manual to assure proper and safe operation of the M2 and to
minimize the risk of personal injury. Be sure to maintain and periodically
calibrate the M2 as described in this manual.
Sampling Method Diffusion
Input Power 19 - 30 VDC
Controls • Three push button switches
• Three magnetic switches for non-intrusive calibration
Weight 4.5 lbs.
Signal Output • 4 to 20 mA, 500 ohms impedance max
• RS-485 Modbus
Operating
Temperature • ESM-01 Type: -10°C to 40 °C
• All Others: -20°C to 50°C
Accuracy ± 5% of full scale
*These are the RKI factory settings. You can change the alarm settings in Configuration Mode. See
“Viewing & Changing M2 Parameters” on page 30.
Table 1: M2 Specifications

M2 Transmitter Operator’s Manual 4
Chapter 2: Description
Overview
This chapter describes external and internal components of the M2 Transmitter.
External Description
This section describes the junction box and all external components of the M2 transmitter.
Figure 1: M2 External Components
Junction Box
The M2’s cast aluminum junction box is dust and weather resistant. The junction box also
protects the M2 and all connections made to it. Use the two 3/4 in. conduit hubs to mount
the detector to the junction box (factory installed in the bottom hub) and connect wiring
from an external device (top hub).
Use the junction box’s two mounting holes to mount the M2 to a vertical surface at the
monitoring site. The window in the cover on the front of the junction box allows you to
view the LCD display and use the magnetic wand to actuate the magnetic control
switches so you can perform non-intrusive calibration. Removing the cover allows you to
access the interior of the junction box.
3/4 NPT
Conduit Hub
Junction Box
Cover
Window
Detector
(Catalytic LEL Detector Shown)
Mounting Hole (2) Magnetic
Wand

5 M2 Transmitter Operator’s Manual
Magnetic Wand
The magnetic wand is a short plastic rod with a magnet in one end. It is used to actuate
the magnetic control switches on the control PCB while the junction box cover is still
installed so that non-intrusive calibration can be performed.
Gas Detector
The gas detector senses the target gas and is mounted in a 3/4” conduit hub on the right
bottom side of the M2. A variety of detectors may be used with the M2. Table 2 below lists
the detectors that can be used with the M2.
Table 2: M2 Detectors
Target Gas, Range Detector(s) Used
Combustible Gas, 0 - 100% LEL • 61-0140RK (Catalytic UL version)
• 61-0140RK-05 (Catalytic CSA version)
Hydrogen, 0 - 100% LEL • NC-6205-01 (Catalytic UL version, hydrogen specific)
• NC-6205-05 (Catalytic CSA version, hydrogen specific)
CH4, 0 - 100% LEL • 61-0190RK-CH4 (IR UL)
HC, 0 - 100% LEL (cal. to propane) • 61-0190RK-HC (IR UL)
CH4, 0 - 100% volume • 61-0192RK-CH4 (IR UL)
CO2, 0 - 5,000 ppm • 61-0191RK-02 (IR UL)
• 61-0198RK-02 (IR)
CO2, 0 - 5% • 61-0191RK-03 (IR UL)
• 61-0198RK-03 (IR)
CO2, 0 - 50% • 61-0191RK-05 (IR UL)
• 61-0198RK-05 (IR)
CO2, 0 - 100% • 61-0191RK-10 (IR UL)
• 61-0198RK-10 (IR)
Oxygen, 0 - 25% • 65-2494RK (capillary)
• 65-2510RK (partial pressure)
• 65-2511RK (capillary)
• 65-2514RK (capillary, CSA)
CO, 0 - 300 ppm • 65-2433RK-05 (CSA)
• 65-2496RK
H2S, 0 - 100 ppm • 65-2423RK-05 (CSA)
• 65-2495RK
NH3, 0 - 75 ppm • 65-2300RK-NH3
AsH3, 0 - 1.5 ppm • 65-2300RK-ASH3
CL2, 0 - 3 ppm • 65-2300RK-CL2
PH3, 0 - 1 ppm • 65-2300RK-PH3
SO2, 0 - 6 ppm • 65-2300RK-SO2

M2 Transmitter Operator’s Manual 6
The catalytic LEL detectors have a 1/2” NPT thread and require a 3/4”NPT x 1/2”NPT
reducer to install in the detector hub. The rest of the detectors have a 3/4” NPT mounting
thread and are installed directly in the detector hub.
The IR combustible detectors are generally used instead of the catalytic combustible
detectors in applications where there may be catalyst poisons such as silicone present or
where oxygen is not present in the monitoring environment.
Some of the detectors have a replaceable plug-in sensor. These detectors are described and
illustrated below.
There are four types of oxygen detectors available, a non-explosion proof partial pressure
type, a non-explosion proof capillary type, a non-explosion proof capillary type with a
replaceable sensor, and an explosion proof (CSA) capillary type with a replaceable sensor.
The capillary type’s output is less susceptible to variations in atmospheric pressure than
the partial pressure type. The CSA type oxygen detector (65-2514RK) and one of the non-
explosion proof capillary type detectors (65-2494RK) have a replaceable plug-in sensor
inside the detector housing while the entire oxygen detector must be removed if
replacement is required for the other two.
Figure 2: 65-2514RK Oxygen Detector, CSA
Flame Arrestor
Guard
Detector Housing Cap
Oxygen Sensor
Detector Housing Body
Cap Gasket

7 M2 Transmitter Operator’s Manual
Figure 3: 65-2494RK Oxygen Detector, Non-Explosion Proof, Capillary Type
Both types of CO and H2S detectors have replaceable plug-in sensors inside the detector
housing. The CO detector includes a charcoal filter disk which is held onto the sensor with
a rubber retaining boot. The charcoal filter disk scrubs out interfering gases to which the
CO sensor responds such as H2S and certain hydrocarbons.
Figure 4: 65-2433RK-05 CO Detector, CSA
Detector Housing Cap
Plug-In Oxygen Sensor
Detector Housing Body
Cap Gasket
Hydrophobic Membrane
Detector Housing
Cap Gasket
CO Sensor
Detector Housing
Cap
Rubber Boot
w/Charcoal Filter Disk

M2 Transmitter Operator’s Manual 8
Figure 5: 65-2496RK CO Detector Non-Explosion Proof
Figure 6: 65-2423RK-05 H2S Detector, CSA
Hydrophobic
Membrane
CO Plug-in Sensor
Charcoal Filter
w/Rubber Boot
Detector Housing Body
Cap Gasket
Detector
Housing Cap
Detector Housing
Cap Gasket
H2S Sensor
Detector Housin
g
Cap

9 M2 Transmitter Operator’s Manual
Figure 7: 65-2495RK H2S Detector Non-Explosion Proof
The construction of the various ESM-01 detectors is similar. Each of the ESM-01 detectors
has a different replaceable plug-in sensor that protrudes through the detector housing
cap. Although ESM-01 detectors look the same except for the plug-in detector, the detector
housing which includes the detector socket and conditioning circuitry is specific to a
sensor type. For example, a detector housing from a Cl2detector cannot be used with an
NH3detector. One of the two detector wires is color coded for each specific detector type.
The ESM-01 detectors include a removable splashguard that screws onto the detector
housing cap. When it is necessary to apply gas to an ESM-01 detector, remove the
splashguard to allow access to the sensor that protrudes through the detector housing cap.
You can then push the appropriate ESM-01 calibration cup onto the sensor.
Figure 8: ESM-01 Type Detector
Cap Gasket
Detector Housing Body
Hydrophobic
Membrane
H2S Plug-in Sensor
Detector
Housing Cap
Detector Housing Body
(different for each detector type)
Cap Gasket
Splash Guard
(removable)
Detector Housing
Cap
Sensor
(different for each detector type)

M2 Transmitter Operator’s Manual 10
Internal Description
This section describes the internal components of the M2. The internal components of the
M2 include the terminal PCB which provides for all the wiring connections to the M2 and
the control PCB which displays the gas reading and has the control buttons.
Figure 9: M2 Internal Components
Terminal PCB
The terminal PCB is encapsulated in epoxy for protection against moisture and physical
damage. It is mounted into the rear of the junction box with three standoffs and rests on a
thin layer of foam. A banana jack is screwed into each of the standoffs and used for
mounting the control PCB. The terminal PCB converts the electrical output from the
detector to a signal which can be displayed by the LCD display, a 4 - 20 mA signal (that is
proportional to the detection range), and an RS-485 Modbus output signal. The 4 - 20 mA
signal may be used by a recording device, gas monitor controller, or programmable
controller. The Modbus output may be used to connect the M2 to a Modbus network. The
terminal PCB also controls three relays, one fail and two gas alarm relays.
Two columns of plug-in style terminal strips are used to make all wiring connections to
the M2. The column on the left consists of the power/signal, detector, and Modbus
terminal strips. The column on the right consists of the relay terminal strips. A 20 position
C NC NO C NC NO C NC NO
ALARM 2 ALARM 1 FAIL
A B C
A B C
RS 485
RS 485
PWR/SIG
PWR/SIG
LEL
LEL
S S
RKI INSTRUMENTS
M2 TRANSMITTER
Control PCB
Push Button
Control Switches
UP/YES
DOWN/NO
UP/YES
DOWN/NO
ENTER
ENTER
Junction Box
Magnetic
Switches
LCD Display
Relay
Terminal
Strips
3/4" NPT Conduit Opening
For Wire Entry
Power/Signal
Terminal Strip
Detector Terminal Strip
(Comb/CO
2
Version Shown)
Modbus
Terminal Strip
Programming
Connector
(Factory Use)
Display Ribbon
Cable Connector
R W G B
R W G B
View with Cover Removed
View With Cover and Control
PCB Removed
Terminal PCB
Termination
Jumper
Fail LED
Alarm 1 LED
Alarm 2 LED
RX LED
TX LED
D
etector Current Pot
(
Comb/CO
2
Type Only,
F
actory Adjust)

11 M2 Transmitter Operator’s Manual
connector at the bottom of the terminal PCB is used to connect the terminal PCB to the
control PCB with a ribbon cable. A 5 position connector on the left side of the terminal
PCB is used by factory or field service personnel to program the M2. On the combustible
and CO2versions of the M2, a factory adjust pot just above the programming connector is
used to set the detector current.
Power/Signal Terminal Strip
The power/signal terminal strip is a three position plug-in style terminal strip located at
the top of the left terminal column. It is used to connect 24 VDC power to the M2 and to
connect the 4 - 20 mA output signal to a device.
The signal output, the S terminal, does not have to be connected for the M2 to function.
The S terminal is used if you want to connect the 4 - 20 mA output signal to another device
such as a gas monitoring controller, chart recorder, or programmable controller (PLC).
Detector Terminal Strip
The detector terminal strip is a four position plug-in style terminal strip and is the middle
terminal strip in the left terminal column. For a combustible or CO2M2, all four terminals
are used to connect the detector to the M2. For a toxic or oxygen M2, only two of the
terminals are used for connecting a detector: two terminals are dedicated for connecting a
toxic detector and two are dedicated for connecting an oxygen detector (only one detector
can be installed).
Figure 10: Detector Terminal Strip
NOTE: The detector is factory-wired to the M2. See “Wiring the M2 Transmitter” on
page 18 for all wiring procedures related to M2.
Modbus Terminal Strip
The Modbus terminal strip is a three position plug-in style terminal strip and is the
bottom terminal strip in the left terminal column. It allows connection of the M2 into a
Modbus network.
C NC NO C NC NO C NC NO
ALARM 2 ALARM 1 FAIL
A B C
RS 485 PWR/SIGLEL S
R W G B
C NC NO C NC NO C NC NO
ALARM 2 ALARM 1 FAIL
A B C
A B C
RS 485
RS 485
PWR/SIG
PWR/SIG
TOXIC OXY
TOXIC OXY S
S
C
omb/CO2Detector
Terminal Strip
Oxy/Toxic Detector
Terminal Strip
A B C
RS 485 PWR/SIG
LEL S
R W G B

M2 Transmitter Operator’s Manual 12
Relay Terminal Strips
The right column of terminal strips consists of, from top to bottom, the fail, alarm 1, and
alarm 2 relay terminal strips. They are three-position plug-in style terminal strips. The
relay terminal strips are used to connect devices such as lights and horns that are
controlled by the relay contacts. The relay contacts are rated at 115 VAC, 5 amps. The relay
contacts may also be used to control higher rated relays.
Termination Jumper
A two pin header with a termination jumper installed is located below the Modbus
terminal strip. The jumper has no function unless the M2 is wired into a Modbus
installation. See “Chapter 8: RS-485 Modbus Output” on page 50 for a description of using
the M2 in a Modbus system.
Control PCB
The LCD display and control switches are located on the control PCB. It is installed on top
of the terminal PCB by lining up its three spacing standoffs with the banana jacks in the
terminal PCB mounting standoffs and pushing it onto the banana jacks. The jacks retain
the control PCB.
LCD Display
The LCD display is located at the top of the control PCB. It indicates the current gas
reading and displays messages and parameters in the M2’s programs.
Control Buttons
The M2 includes three push button switches that allow you to enter the M2’s operating
modes, navigate through the modes, update settings, and save changes to the settings.
The push button switches are located along the bottom edge of the control PCB (see
Figure 9). The UP/YES button is on the left, the DOWN/NO button is in the middle, and
the ENTER button is on the right.
Just above each push button switch is a magnetic switch with the same function as the
push button switch below it. The magnetic switches are for use in non-intrusive
calibration. They are actuated by bringing the magnetic wand close enough to them to
Table 3: M2 Control Button Functions
Switch Function
UP (YES) • Saves settings
• Changes the displayed setting
• Enters the Calibration Program
• Enters Gas Type Mode (press with DOWN/NO button)
• Enters Configuration Mode (press with ENTER button)
DOWN (NO) • Cancels setting changes
• Changes the displayed setting
• Enters Gas Type Mode (press with UP/YES button)
• Enters Modbus Mode (press with ENTER button)
• Displays the Information Screen
ENTER • Initiates operations
• Enters Configuration Mode (press with UP/YES button)
• Enters Modbus Mode (press with DOWN/NO button)
• Functions as an alarm reset switch

13 M2 Transmitter Operator’s Manual
actuate them. Although the magnetic switches have the same functions as the push button
switches, it is not practical to use them for operations other than calibration because it is
not possible to actuate two magnetic switches at once with only one magnetic wand. Since
displaying the Information Screen only requires the use of one switch, the wand may be
used to show the Information Screen (see “Information Screen” on page 25).
Status LEDs
The M2 includes five status LEDs that are located above the display (see Figure 9).
• Fail LED
The fail LED turns on when the M2 is experiencing a fail condition. A fail condition
can be caused by a detector failure or low detector signal.
• Alarm 1 LED
The alarm 1 LED is on when the M2 is experiencing an alarm 1 condition.
• Alarm 2 LED
The alarm 2 LED is on when the M2 is experiencing an alarm 2 condition.
• RX & TX LED’s
These LED’s indicate data being received (RX) and transmitted (TX) when the M2’s
Modbus output is operating.

M2 Transmitter Operator’s Manual 14
Chapter 3: Installation & Startup
Overview
This chapter describes procedures to mount the M2 Transmitter in the monitoring
environment and wire it to input power and devices.
Mounting the M2 Transmitter
1. Select a mounting site that is representative of the monitoring environment. Consider
the following when you select the mounting site.
• Select a site where the M2 is not likely to be bumped or disturbed. Make sure
there is sufficient room to perform start-up, maintenance, and calibration
procedures.
• Select a site where the target gas is likely to be found first. For lighter gases,
mount the detector near the ceiling; for heavier gases, mount the detector near the
floor.
2. At the monitoring site, use #10 screws through the junction box’s two mounting holes
to secure the junction box to a vertical surface. Figure 11 - Figure 17 show the outline
and mounting dimensions for each version of the M2. Mount the M2 with the detector
facing down as shown in the following figures.
Figure 11: Outline & Mounting Dimensions, Catalytic LEL
4.60
6.10
1
.10
.25 Dia. Mounting
Hole, 2X
3/4 NPT Condu
it
Hu
b
7.7 max
2.75
5.20
1 1/2-20 For
Calibration Cup 2.3 max
5.46

15 M2 Transmitter Operator’s Manual
Figure 12: Outline & Mounting Dimensions, IR Combustible & CO2
Figure 13: Outline & Mounting Dimensions, Oxygen, Partial Pressure Type
1.9 max
.25 Dia. Mounting
Hole, 2X
3/4 NPT Conduit
Hub
3.94
1.1
5.46
2.75
5.2
IR Detector
6
.1
7.3 max
4.60
6.10
1
.10
.25 Dia. Mounting
Hole, 2X
3/4 NPT Condu
it
Hu
b
8.1 max
2.75
5.20
1 1/2-20 For
Calibration Cup 2.6 max
5.46