RKI Instruments 65-2670-XX-04 User manual

RKI Instruments, Inc.
www.rkiinstruments.com
65-2670-XX-04
M2A Transmitter
Operator’s Manual
Part Number: 71-0518
Revision: D
Released: 6/24/21

65-2670-XX-04 M2A 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.

65-2670-XX-04 M2A 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

65-2670-XX-04 M2A Transmitter Operator’s Manual
Table of Contents
Chapter 1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
About the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
About this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Chapter 2: Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
External Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Internal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Chapter 3: Installation & Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Mounting the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Wiring the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Chapter 4: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Information Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4 - 20 mA Signal Output Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Alarm Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Chapter 5: Configuration Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Viewing & Changing M2A Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Chapter 6: Gas Type Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Selecting the Gas Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

65-2670-XX-04 M2A Transmitter Operator’s Manual
Chapter 7: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Calibration Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Replacing Components of the Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Chapter 8: RS-485 Modbus Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Wiring the M2A in a Modbus System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Using the M2A in a 4-wire Modbus System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Modbus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Supported Modbus Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Chapter 9: Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Appendix A: Control Button Quick Reference Guide. . . . . . . . . . . . . . . . . . . . . . . . . 57
Appendix B: PLC and DCS Device Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Appendix C: Function Code 16 Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

6 65-2670-XX-04 M2A Transmitter Operator’s Manual
Chapter 1: Introduction
Overview
This chapter briefly describes the 65-2670-XX-04 M2A Transmitter. This chapter also describes the
65-2670-XX-04 M2A Transmitter Operator’s Manual (this document). Table 1 at the end of this
chapter lists the specifications for the M2A.
About the M2A Transmitter
The M2A 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 M2A displays the current gas reading on an OLED 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 M2A 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 M2A 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.

65-2670-XX-04 M2A Transmitter Operator’s Manual 7
Specifications
Table 1 lists specifications for the M2A.
Table 1: M2A Specifications
Target Gas/Detection Range • Ammonia (NH3): 0 - 75.0 ppm, 0.1 ppm increments
• Ammonia (NH3): 0 - 100 ppm, 1 ppm increments
• Ammonia (NH3): 0 - 200 ppm, 1 ppm increments
• Ammonia (NH3): 0 - 500 ppm, 1 ppm increments
•Chlorine(Cl
2): 0 - 3.00 ppm, 0.01 ppm increments
•Chlorine(Cl
2): 0 - 5.00 ppm, 0.01 ppm increments
•Chlorine(Cl
2): 0 - 10.0 ppm, 0.1 ppm increments
• Chlorine Dioxide (ClO2): 0 - 1.00 ppm, 0.01 ppm increments
• Chlorine Dioxide (ClO2): 0 - 3.00 ppm, 0.01 ppm increments
• Chlorine Dioxide (ClO2): 0 - 3.00 ppm, 0.01 ppm increments
Alarm Settings
(Alarm 1/Alarm 2)*
• Ammonia (0 - 75.0 ppm and 0 - 100 ppm): 12 ppm / 25 ppm
• Ammonia (0 - 200 ppm): 25 ppm / 35 ppm
• Ammonia (0 - 500 ppm): 35 ppm / 300 ppm
• Chlorine (0 - 3.00 ppm): 0.50 ppm / 1.00 ppm
• Chlorine (0 - 5.00 ppm): 0.50 ppm / 1.50 ppm
• Chlorine (0 - 10.0 ppm): 1.0 ppm / 3.0 ppm
• Chlorine Dioxide (0 - 1.00 ppm): 0.10 ppm / 0.30 ppm
• Chlorine Dioxide (0 - 3.00 ppm): 0.30 ppm / 1.00 ppm
• Chlorine Dioxide (0 - 5.00 ppm): 0.50 ppm / 1.00 ppm
Sampling Method Diffusion
Flow Rate for Calibration 0.25 LPM (using a 0.5 LPM regulator that is normally recommended for
M2As will result in an inaccurate calibration)
Input Power 10 - 30 VDC
Controls • Three push button switches
• Three magnetic switches for non-intrusive calibration
Weight 5.5 lbs.
Signal Output • 4 to 20 mA with impedance maximums listed below
-12 VDC: 500 ohms impedance max
-24 VDC: 1000 ohms impedance max
• RS-485 Modbus
Operating Temperature -20°C to 40°C
Accuracy ± 10% of reading or ± 5% of full scale (whichever is greater)
*These are the RKI factory settings. You can change the alarm settings in Configuration Mode. See
“Viewing & Changing M2A Parameters” on page 29.

8 65-2670-XX-04 M2A Transmitter Operator’s Manual
WARNING: When using the M2A, you must follow the instructions and warnings in this manual
to assure proper and safe operation of the M2A and to minimize the risk of personal
injury. Be sure to maintain and periodically calibrate the M2A as described in this
manual.

65-2670-XX-04 M2A Transmitter Operator’s Manual 9
Chapter 2: Description
Overview
This chapter describes the components of the M2A transmitter. The transmitter is a 4 - 20 mA type
detector head. It consists of the detector, calibration adapter/splash guard, terminal PCB, the M2A
junction box, and the detector junction box. The two-junction-box configuration is intended for
situations where the detector needs to be installed at an inaccessible location. The detector junction
box can be installed at the inaccessible location and the M2A junction box can be installed in a more
readily accessible area.
External Description
This section describes the junction boxes and all external components of the M2A transmitter.
Magnetic
Wand
Terminal
Strip
3/4 NPT Conduit Hub
3/4 NPT
Conduit Hub
Detector
Detector
Junction Box
Calibration Adapter/
Splash Guard
M2A
Junction Box
Mounting Slot (2x)
Window
3/4 NPT
Conduit Hub
Figure 1: M2A External Components

10 65-2670-XX-04 M2A Transmitter Operator’s Manual
M2A Junction Box
The M2A’s cast aluminum junction box is dust and weather resistant. The junction box also protects
the M2A and all connections made to it. Use the three 3/4 NPT conduit hubs to wire the remotely
installed combustible gas detector and connect wiring from an external device, typically an RKI
controller. The top hub is shipped with a factory installed and sealed conduit plug to avoid leaks into
the junction box. If necessary, the conduit plug can be removed and the top hub can be used for wiring.
WARNING: If the top conduit hub is used for wiring, be sure to seal the threads to ensure water
does not enter the junction box. See “Wiring the M2A Transmitter” on page 18 for
complete wiring instructions.
Use the junction box’s two mounting holes to mount the M2A 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 OLED 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.
Detector Junction Box
The detector junction box is intended to be installed remotely from the M2A junction box. The
detector is factory installed in the bottom 3/4 NPT conduit hub. A terminal strip is provided for wiring
connections and the detector is factory wired to one side of this terminal strip. The other side of the
terminal strip is for user-supplied wiring to the detector terminal strip located in the M2A junction box.
This wiring should go through the top 3/4 NPT conduit hub. Three spacers installed on the back of the
junction box controls the distance of the junction box from a mounting surface. A ground boss near the
top conduit hub provides an external earth ground connection.
Detector
The CT-7 style detector consists of the detector housing body, detector housing cap, cap gasket, and
the plug-in sensor.
The table below outlines the M2A part numbers and replacement detector part numbers for the
detectors.
Target Gas, Range M2A Part Number Detector Used
Cl2, 0 - 3 ppm 65-2670-CL2-04 65-2302-CL2
Cl2, 0 - 10 ppm 65-2670-CL210-4 65-2302-CL2-10
ClO2, 0 - 1 ppm 65-2670-CLO2-04 65-2302-CLO2
ClO2, 0 - 3 ppm 65-2670-CLO2-34 65-2302-CLO2-3
NH3, 0 - 100 ppm 65-2670-NH3-1-4 65-2302-NH3-100
NH3, 0 - 500 ppm 65-2670-NH3-5-4 65-2302-NH3-500

65-2670-XX-04 M2A Transmitter Operator’s Manual 11
Detector Housing Body
The detector housing body protects the electronic components within the housing. Use the mounting
threads at the top of the housing to screw the detector into the 3/4 NPT hub on the bottom of the
detector junction box. Two wires extend from the top of the detector housing body. Use these wires to
connect the detector to the terminal strip. One of the wires is color-coded for each detector type.
The housing includes a four-socket pattern. This socket pattern accepts the sensor’s four pins to secure
the sensor within the detector housing. A pre-amplifier, located between the sockets and two
interconnect wires, conditions the sensor’s signal before the signal reaches the controller.
Housing Cap & Cap Gasket
The housing cap screws onto the detector housing. An adhesive backed gasket inside the detector
housing cap helps ensure that the sensor remains plugged into the detector housing body.It retains the
plug-in sensor and protects it from damage. Unscrew the detector cap to access the plug-in sensor for
maintenance or replacement. A cap gasket seals the interface between the housing and cap.
Plug-In Sensor
The sensor is secured within the detector assembly by the housing cap. Through a series of chemical
and electrical reactions, the sensor produces an electrical output that corresponds to the detection range
of the transmitter.
Calibration Adapter/Splash Guard
A calibration adapter/splash guard is installed on the detector. A fitting at the bottom of the calibration
adapter/splash guard allows a length of tubing to be connected for calibration and routed to a more
easily accessible location (near the M2A junction box is optimal for ease of calibration). The
calibration adapter/splash guard also protects the detector from splashing water or direct water spray.
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.
Hydrophobic Membrane
Plug-in Sensor
Detector
Housing Cap
Cap Gasket
Detector Housing Body
(different for each detector type)
Figure 2: Detector Component Location

12 65-2670-XX-04 M2A Transmitter Operator’s Manual
Internal Description
This section describes the internal components of the M2A. The internal components of the M2A
include the terminal PCB which provides for all the wiring connections to the M2A and the control
PCB which displays the gas reading and has the control buttons.
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 OLED
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 M2A 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 M2A. 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 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 M2A.
NO
Control PCB
M2A JunctionBox
Terminal PCB
3/4 NPT Conduit
Opening for Wire Entry
M2A TRANSMITTER
RKI INSTRUMENTS
3/4 NPT Conduit Opening, Plugged
Figure 3: M2A Internal Components

65-2670-XX-04 M2A Transmitter Operator’s Manual 13
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 M2A 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 M2A 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. The two terminals labeled “TOXIC” are used to connect the detector to the
M2A.
NOTE: The detector is factory-wired to the M2A. See “Wiring the M2A Transmitter” on page 18
for all wiring procedures related to M2A.
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 M2A into a Modbus network.
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.
Figure 4: Terminal PCB Component Location
C NC NO
ALARM 1 C NC NO
ALARM 2
C NC NO FAIL
Modbus Terminal Strip
Ground Jumper
Programming Connector
(Factory Use)
Termination Jumper
Relay
Terminal
Strips
RS 485
A B C - S +
PWR/SIG
+
Ribbon Cable Connector
Power/Signal Terminal Strip
Detector Terminal Strip
TOXIC OXY
+

14 65-2670-XX-04 M2A Transmitter Operator’s Manual
Termination Jumper
A two pin header with a termination jumper installed is located below the Modbus terminal strip.
Leave this jumper installed unless directed to remove it for a Modbus installation. See “Chapter 8: RS-
485 Modbus Output” on page 44 for a description of using the M2A in a Modbus system.
Ground Jumper
A two pin header with a jumper installed is located along the left side of the terminal PCB. Leave this
jumper installed unless directed to remove it for a Modbus installation. See “Chapter 8: RS-485
Modbus Output” on page 44 for a description of using the M2A in a Modbus system.
Control PCB
The OLED 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.
OLED Display
The OLED display is located at the top of the control PCB. It indicates the current gas reading and
displays messages and parameters in the M2A’s programs.
Control Buttons
The M2A includes three push button switches that allow you to enter the M2A’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 5). The UP/YES button is
on the left, the DOWN/NO button is in the middle, and the ENTER button is on the right.
Figure 5: Control PCB Component Location
ENTER
DOWN/NO
UP/YES
Push Button
Control Switches
Magnetic Switches
ENTER
UP/YES
DOWN/NO
Alarm 1 LED Alarm 2 LED
Fail LED RX LED
TX LED
M2ATRANSMITTER
RKI INSTRUMENTS
OLED Display

65-2670-XX-04 M2A Transmitter Operator’s Manual 15
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 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 24).
Status LEDs
The M2A includes five status LEDs that are located above the display (see Figure 5).
• Fail LED
The fail LED turns on when the M2A 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 M2A is experiencing an alarm 1 condition.
• Alarm 2 LED
The alarm 2 LED is on when the M2A is experiencing an alarm 2 condition.
• RX & TX LED’s
These LED’s indicate data being received (RX) and transmitted (TX) when the M2A’s Modbus
output is operating.
Table 2: M2A 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

16 65-2670-XX-04 M2A Transmitter Operator’s Manual
Chapter 3: Installation & Startup
Overview
This chapter describes procedures to mount the M2A Transmitter in the monitoring environment and
wire it to input power and devices.
Mounting the M2A Transmitter
1. Select a mounting site that is representative of the monitoring environment. Consider the
following when you select the mounting site.
• For the M2A junction box, select a site where the junction box is not likely to be bumped or
disturbed. Make sure there is sufficient room to perform start-up, maintenance, and calibration
procedures. The site should be easily accessible.
• For the detector junction box, 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.
• The junction boxes should be mounted no further than 200 feet from each other.
2. Use #10 screws through the M2A junction box’s two mounting slots to secure the junction box to a
vertical surface. Figure 6 shows the outline and mounting dimensions the M2A junction box.
Figure 7 shows the outline and mounting dimensions for the detector junction box. Mount the
detector junction box with the detector facing down as shown in Figure 7.
Figure 6: M2A Junction Box Dimensions
.30 (2X)
4.59
5.86
1.02
3/4 NPT
Conduit Hub,
3X
5.00
2.41
.47 (2X)
5.23

65-2670-XX-04 M2A Transmitter Operator’s Manual 17
3. Tubing from the calibration adapter/splash guard must be 1/8 inch I.D. x 1/4 inch O.D. Teflon.
Install a small piece of 3/16 inch I.D. flexible polyurethane tubing to each end of the Teflon tubing.
Use the flexible tubing on one end to connect to the calibration adapter/splash guard. Route the
Teflon tubing to an accessible area that is close to the M2A junction box. Use the flexible tubing
on the other end to connect to a regulator during calibration. See the “Chapter 9: Parts List” on
page 55 for available tubing.
.382.70
Detector
Calibration
Adapter/
Splash
Guard
Ø3.65
3/4 Conduit Hub
9.70 Max
5.25
1.13
Rubber
Spacer,
3X
Figure 7: Detector Junction Box Dimensions

18 65-2670-XX-04 M2A Transmitter Operator’s Manual
Wiring the M2A Transmitter
Wiring the Detector to the M2A
WARNING: Always verify that the power to the M2A is off before you make wiring connections.
1. Confirm that no power is being applied to the M2A.
2. Remove the detector junction box’s cover from the junction box.
3. Remove the M2A junction box’s cover from the junction box.
4. Grasp the control PCB by its edges.
5. Gently pull until the control PCB is pulled away from the banana jacks. Take care not to pull too
hard and damage the cable which connects the control and terminal PCBs.
6. Let the control PCB hang by the cable. The terminal strips are now visible on the terminal PCB.
The control PCB may be left hanging while wiring is done. If desired, the control PCB may be
disconnected from the cable and set aside while wiring.
7. To maintain the M2A junction box’s NEMA 4X environmental rating and prevent water from
entering the junction box through the conduit hubs, use appropriate construction technique.
8. Guide a two-conductor, shielded cable or two wires in conduit through the top conduit hub of the
detector junction box. To make wiring more convenient, use wire colors that correspond to the
detector wire colors: red and black.
9. Connect the wires to the terminal block in the detector junction box.
10. Secure the detector junction box’s cover to the junction box.
11. Guide the other end of the two-conductor, shielded cable or two wires in conduit through the
bottom conduit hub of the M2A junction box.
WARNING: If the top conduit hub is used for wiring, be sure to seal the threads to ensure water
does not enter the junction box.
12. To gain access to a plug-in terminal strip for wiring, pull it out of its socket by grasping the wall
between two terminal positions with needle nose pliers and pulling. Be careful not to exert too
much force on the wall to avoid damage to the terminal strip. The detector terminal strip and the
alarm 1 relay terminal strip may be removed by grasping them with your fingers if the adjacent
terminal strips have been removed.
Max Distance to M2A
w/18 Gauge Wire
Max Distance to M2A
w/16 Gauge Wire
Max Distance to M2A
w/14 Gauge Wire
500 ft. 1,000 ft. 2,000 ft.

65-2670-XX-04 M2A Transmitter Operator’s Manual 19
13. Pull out the detector terminal strip and connect the two wires to the terminal strip as follows (see
Figure 8).
• Connect the wire corresponding to the detector’s red wire to the TOXIC “+” terminal.
• Connect the wire corresponding to the detector’s black wire to the TOXIC “-” terminal.
CAUTION: If shielded cable is used, leave the cable shield’s drain wire disconnected and
insulated at the detector junction box. You will connect the opposite end of the cable’s
drain wire to the M2A junction box’s chassis (earth) ground.
14. Reinstall the detector terminal strip into its socket.
See
Table
PWR/SIG
Detector
Terminal
Strip
C NC NO
ALARM 1 C NC NO
ALARM 2
C NC NO FAIL
+
- S +
+ TOXIC OXY
Cl2
Gas Type + Wire
Black
Cable
Shield
Detector J-Box
See
Table
Detector
Gas Type Table
Black
violetCLO2 red
yellow
NH3
M2A
J-Box
Calibration Adapter/Splash Guard
RS 485
A B C
Figure 8: Wiring the Detector to the M2A

20 65-2670-XX-04 M2A Transmitter Operator’s Manual
15. If shielded cable is used between the detector junction box and the M2A junction box, connect the
cable’s drain wire to an available chassis (earth) ground at the M2A junction box. Do not connect
the shield drain wire at the detector junction box.
Wiring the M2A to a Controller and Alarm Devices
1. Guide multi conductor shielded cable or cables or wires in conduit through the left conduit hub of
the M2A junction box. The number of cables or wires needed will depend on whether the M2A is
wired to a gas monitoring controller or just to power, whether any relays are used, and whether the
Modbus output is used.
WARNING: If the top conduit hub is used for wiring, be sure to seal the threads to ensure water
does not enter the junction box.
NOTE: If the M2A is being wired to a PLC or DCS device, see “Appendix B: PLC and DCS Device
Wiring” on page 58, then continue with step 8.
Use the following recommendations to determine how to wire the M2A:
• If Modbus connections will not be used and only the PWR/SIG connections will be used, use a
two or three conductor shielded cable or two or three wires in conduit for connections to the
power/signal terminal strip depending on whether or not the signal (S) terminal is used. The S
terminal has a 4 - 20 mA output, but if you do not need to monitor this signal and do not con-
nect to the S terminal to access this signal, the M2A will still function completely.
• If the PWR/SIG connections and one or more relays are used, route the connections to the
M2A in conduit. Use shielded cable in the conduit for the PWR/SIG connections and
unshielded cable or individual wires for the relay connections. Make sure any wire or cable
used for relay wiring is appropriately rated for the power that it will carry.
CAUTION: If shielded cable is used for the PWR/SIG connections, leave the cable shield’s drain
wire insulated and disconnected at the M2A junction box. You will connect the
opposite end of the cable’s drain wire at the controller or device.
• If the M2A will be wired into a Modbus network, see “Chapter 8: RS-485 Modbus Output” on
page 44.
See Figure 9 below for field wiring connections to the M2A.
Table 3: Wire Size for PWR/SIG Connections
Max Distance to Controller
w/18 Gauge Wire
Max Distance to Controller
w/16 Gauge Wire
Max Distance to Controller
w/14 Gauge Wire
2,500 ft. 5,000 ft. 8,000 ft.