RKI Instruments M2A User manual

RKI Instruments, Inc.
www.rkiinstruments.com
M2A Transmitter
UL 2075 Version
Operator’s Manual
Part Number: 71-0379
Revision: P2
Released: 6/25/21

2M2A 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.

M2A Transmitter Operator’s Manual 3
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

4M2A 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
External Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Internal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Chapter 3: Installation & Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Mounting the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Wiring the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Chapter 4: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Information Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4 - 20 mA Signal Output Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Alarm Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Chapter 5: Configuration Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Viewing & Changing M2A Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Chapter 6: Gas Type Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Selecting the Gas Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

M2A Transmitter Operator’s Manual 5
Chapter 7: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Calibration Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Replacing Components of the M2A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Appendix A: Control Button Quick Reference Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Appendix B: PLC and DCS Device Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

6M2A Transmitter Operator’s Manual
Chapter 1: Introduction
Overview
This chapter briefly describes the M2A Transmitter. This chapter also describes the 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 recording device.
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.
Three operating modes allow you to display and change setup and calibration settings and change the gas type.
They are Calibration Mode, Configuration Mode, and Gas Type 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.

M2A Transmitter Operator’s Manual 7
Specifications
Table 1 lists specifications for the M2A.
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.
Table 1: M2A Specifications
Target Gas/Detection Range CH4: 0 - 100% LEL, 1% LEL increments
Alarm Settings
(Alarm 1/Alarm 2)
10 %LEL/50 %LEL
Construction (housing) Explosion-proof Junction Box, NEMA 4X
Area Classification Explosion-proof for Class I, Groups B, C, and D
Sampling Method Diffusion
Input Power 10 - 30 VDC
Controls • Three push button switches
• Three magnetic switches for non-intrusive calibration
Weight 4.5 lbs.
Signal Output • 4 to 20 mA with impedance maximums listed below
-12 VDC input: 500 ohms impedance max
-24 VDC input: 1000 ohms impedance max
Operating Temperature -40°C to 50°C
Accuracy ± 5% of reading or ± 2% 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 24.

8M2A Transmitter Operator’s Manual
Chapter 2: Description
Overview
This chapter describes external and internal components of the M2A Transmitter.
External Description
This section describes the junction box and all external components of the M2A transmitter.
Figure 1: M2A External Components
Magnetic
Wand
Junction Box Cover
Detector
Window
Mounting Slot (2x)
3/4 NPT Conduit Hub, Plugged
3/4 NPT
Conduit Hub

M2A Transmitter Operator’s Manual 9
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 ports to mount the detector to the junction box
(factory installed in the bottom port) and connect wiring from an external device (left port). The top port 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 port can be used for wiring.
WARNING: If the top conduit port 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 15 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.
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 NPT conduit port on the right bottom side of the
M2A. 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.
The IR detector has a replaceable plug-in sensor inside the detector housing. A sensor gasket seals the sensor
face to the detector housing cap.
Figure 2: Detector Component Location
Cap Gasket
Detector Housing Body
Flame Arrestor
Guard
Detector Housing Cap
Plug-In IR Sensor

10 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.
Figure 3: M2A 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 OLED display and a 4 - 20 mA signal (that is
proportional to the detection range). The 4 - 20 mA signal may be used by a recording device. 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. On the combustible and CO2versions of the
M2A, a factory adjust pot just above the programming connector is used to set the detector current.
NO
Control PCB
Junction Box
Terminal PCB
3/4 NPT Conduit
Opening for Wire Entry
M2A TRANSMITTER
RKI INSTRUMENTS
3/4 NPT Conduit Opening, Plugged

M2A Transmitter Operator’s Manual 11
Figure 4: Terminal PCB Component Location
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 a recording device.
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.
NOTE: The detector is factory-wired to the M2A. See “Wiring the M2A Transmitter” on page 15 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. This terminal strip is not used in this version of the M2A.
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. This jumper
has no function in this version of the M2A and should be left alone.
Relay
Terminal
Strips
Termination Jumper
Ribbon Cable Connector
Detector Terminal Strip
Detector Current Adjust Pot
(Factory Use)
Power/Signal Terminal Strip
Programming Connector
(Factory Use)
Ground Jumper
Modbus Terminal Strip
C NC NO
ALARM 1 C NC NO
ALARM 2
C NC NO FAIL
- S +
A B C
RS 485 PWR/SIG
R W G B
LEL

12 M2A Transmitter Operator’s Manual
Ground Jumper
A two pin header with a jumper installed is located along the left side of the terminal PCB. This jumper has no
function in this version of the M2A and should be left alone.
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 3). 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 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 19).
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)
• Displays the Information Screen
ENTER • Initiates operations
• Enters Configuration Mode (press with UP/YES button)
• Functions as an alarm reset switch

M2A Transmitter Operator’s Manual 13
Status LEDs
The M2A includes five status LEDs that are located above the display (see Figure 3).
• 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 do not have any function in this version of the M2A.

14 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.
• Select a site where the M2A 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 5 shows the outline and mounting dimensions. Mount the M2A with the
detector facing down as shown in the figure below.
Figure 5: Outline & Mounting Dimensions
3/4 NPT
Conduit Port,
Plugged
3/4 NPT
Conduit Port
8.6 max
3.4 max
4.59
1.02
5.86
.30 (2X)
5.00
2.41
.47 (2X)
5.23

M2A Transmitter Operator’s Manual 15
Wiring the M2A Transmitter
WARNING: Always verify that the power source is OFF before making any wiring connections.
1. Remove the junction box cover.
2. Grasp the control PCB by its edges.
3. 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.
4. 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.
5. The detector leads are factory wired. Verify that the detector leads are wired to the detector terminal strip as
shown in the figure below.
• Red wire to terminal labeled LEL R, white wire to terminal labeled LEL W, green wire to terminal
labeled LEL G, black wire to terminal labeled LEL B.
Figure 6: Detector Wiring
6. 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.
WARNING: If the M2A is installed in a hazardous location, use appropriately rated conduit, conduit
fittings, and appropriate construction technique that complies with the local electrical code.
In addition, use appropriately rated conduit, conduit fittings, and appropriate construction
technique to maintain the NEMA 4X environmental rating of the junction box and avoid
water entering the junction box at the conduit ports.
Black
Green
White
Red
- S +
A B C
RS 485 PWR/SIG
R W G B
LEL C NC NO
ALARM 1 C NC NO
ALARM 2
C NC NO FAIL

16 M2A Transmitter Operator’s Manual
WARNING: To maintain the explosion proof classification of the M2A, a conduit seal must be used within
18 inches of the junction box conduit hub used for wiring. Do not install the detector in an
environment with acetic acid.
7. Guide multi conductor shielded cable or cables or wires in conduit through the conduit port on the left side
of the junction box.
WARNING: If the top conduit port is used for wiring, be sure to seal the threads to ensure water does not
enter the junction box. A conduit seal, which is normally required to maintain the junction
box’s hazardous location rating, will also help to prevent water from entering through the top
port.
The number of cables or wires needed will depend on whether the M2A is wired to a recording device or just
to power and whether any relays are used.
NOTE: If the M2A is being wired to a PLC or DCS device, see “Appendix B: PLC and DCS Device Wiring”
on page 38, then continue with step 8.
Use the following recommendations to determine how to wire the M2A:
• If 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 connect 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.
NOTE: If shielded cable is used for the PWR/SIG connections, leave the cable shield’s drain wire insulated
and disconnected at the M2A. You will connect the opposite end of the cable’s drain wire at the
recording device.
Table 3: Wire Size for PWR/SIG Connections
Max Distance to Recording
Device or Power
w/18 Gauge Wire
Max Distance to Recording
Device or Power
w/16 Gauge Wire
Max Distance to Recording
Device or Power
w/14 Gauge Wire
2,500 ft. 5,000 ft. 8,000 ft.

M2A Transmitter Operator’s Manual 17
See Figure 7 below for field wiring connections to the M2A.
Figure 7: Wiring the M2A to a Recording Device and Alarm Devices
8. Re-install the control PCB (and ribbon cable if necessary). Be sure the ribbon cable is routed down below
the control PCB so it will not be damaged by the cover when it is screwed back on.
9. Secure the junction box cover to the junction box.
10. Make recording device and relay connections as appropriate. If shielded cable is used for the PWR/SIG
connections, connect the cable shield’s drain wire to an available chassis ground at the recording device.
Start Up
Introducing Incoming Power
1. Complete the installation procedures described earlier in this manual.
2. Verify that all wiring connections are correct and secure.
3. Turn on the incoming power.
4. If necessary, turn on the recording device that is connected to the M2A.
5. The OLED display will indicate the firmware version when the M2A is first powered up and will then count
down a one minute warm-up period before normal operation begins. During normal operation, the display
will indicate the target gas and current gas reading. Verify that the display is indicating the target gas and
current gas reading after the warm-up period is complete and normal operation begins.
NOTE: Allow the M2A’s detector to warm up for 15 minutes before you continue with the next section,
“Adjusting the Fresh Air Reading.”
Alarm Device
Power
Fail Alarm
Device
Alarm 1
Alarm Device
Recording Device
Terminals
Typical Alarm
Wiring Shown
(24 VDC) +
4-20mAIn(S)
(24 VDC) -
- S +
A B C
RS485 PWR/SIG
R W G B
LEL
See
Detector
Wiring
C NC NO
ALARM 1 C NC NO
ALARM 2
C NC NO FAIL
Alarm 2
Alarm Device
METHANE
0 %LEL

18 M2A Transmitter Operator’s Manual
Adjusting the Fresh Air Reading
When the M2A is shipped from RKI Instruments, Inc., it is factory calibrated. If a full calibration is desired at
startup, see “Calibration” on page 32.
Verify that the M2A is in a fresh air environment (environment known to be free of the target gas and
combustible or toxic gas vapors and of normal oxygen content, 20.9%).
CAUTION: If you suspect the presence of combustible gas, CO2, toxic gas, or that the oxygen content is not
normal in the monitoring environment, use the calibration kit and the zero air calibration
cylinder to introduce “fresh air” to the detector and verify an accurate fresh air setting. See the
“Calibration” on page 32 or “Replacing Components of the M2A” on page 34 for instructions
on how to use a zero air cylinder when performing a fresh air adjustment.
Non-Intrusive Fresh Air Signal Adjustment
If the M2A is installed in a classified area and non-intrusive zero adjustment is required, follow the instructions
below, but do not remove the junction box cover. Use the magnetic wand accessory to actuate the magnetic
switches instead of pushing the control switch buttons. To actuate a magnetic switch and perform the same
operation as pressing a control switch button, touch the magnet in the end of the magnetic wand to the M2A’s
glass cover directly over the magnetic switch you wish to actuate. Touching the glass and removing the wand is
the same as pressing and releasing a button. Touching the glass and keeping the wand in place is the same as
pressing and holding a button.
WARNING: The M2A is not an active gas monitoring device during the fresh air adjustment procedure.
The 4-20 mA output signal will “freeze” at 3.5 mA for a toxic, combustible gas, or CO2M2A,
or at 17.4 mA for an oxygen M2A, and all relays will remain in their non-alarm state while
the M2A is in Calibration Mode. The output signal will not indicate current readings and the
relays will not resume operating normally until the M2A is in normal operation again.
NOTE: While in the calibration program, if there is no switch activity for the calibration time-out period the
unit will return to normal operation. The factory set time-out is 15 minutes. If you want a different
time-out period, see “Viewing & Changing M2A Parameters” on page 24 for instructions to change
the calibration time-out.
Adjusting the Fresh Air Reading
1. While in normal operation, press and hold the UP/YES button for 5 seconds to enter Calibration Mode.
Release the button when the following screen appears.
2. Press and release the UP/YES button to continue. The display will indicate the target gas and CAL Mode for
a few seconds before showing FreshAir Adjust?.
3. Press and release the UP/YES button. ENTER will alternate with FreshAir on the top display line and the
current gas reading will be on the bottom display line.
4. Press and release the ENTER button. The M2A will perform a zero operation and the display will indicate
SPAN w/Cal Gas?.
5. Press and release the DOWN/NO button. The display will indicate Leaving CAL Mode and the M2A will
return to normal operation.
Calib?
YES/NO

M2A Transmitter Operator’s Manual 19
Chapter 4: Operation
Overview
This chapter describes the M2A in normal operation. This chapter also describes the M2A in alarm 1, alarm 2,
and fail conditions and suggests responses to these conditions.
Normal Operation
Normal operation is defined as follows:
• The start-up procedure is complete.
• The M2A is not indicating an alarm 1, alarm 2, or fail condition.
• The M2A is not in Calibration, Configuration, or Gas Type modes.
During normal operation, the M2A simultaneously displays the current gas reading, unit of measure, and target
gas. The example below illustrates a typical combustible gas M2A.
Information Screen
The Information Screen displays the M2A’s operating voltage and firmware and hardware information. To
display the Information Screen, do the following:
1. Press and hold the DOWN/NO button for 3 seconds. The Information Screen will appear.
2. Continue holding the DOWN/NO button to keep the Information Screen on the display. The top line
indicates the operating voltage that is connected to the M2A. The second line indicates the firmware that is
running, version 6.0 in this example, and the M2A’s hardware version, version 2A in this example. This
information may be useful if you need to contact the factory with questions about the M2A.
3. Release the DOWN/NO button when you are done viewing the Information Screen. The display will return
to the normal operation screen within a couple of seconds.
METHANE
0 %LEL
24.2V
v6.0L 2A

20 M2A Transmitter Operator’s Manual
4 - 20 mA Signal Output Operation
The output at the S terminal of the power/signal terminal strip is a 4 - 20 mA signal that corresponds to the
detection range of the M2A. During normal operation, this signal tracks the gas concentration on the OLED
display.
There are several circumstances where the signal output will not track the display reading but will behave as
follows:
• When the M2A is in its warm-up period, the signal output will be fixed at 1.2 mA.
• When the M2A’s gas type is changed, the M2A will enter Configuration Mode for you to verify the
parameter settings. When you exit Configuration Mode, the display will indicate NEEDS CALIBRATION
and will continue to indicate this until Calibration Mode is entered and a calibration is performed. In this
situation, the signal output will be fixed at 3.5 mA from the time Gas Type Mode is entered until the M2A is
calibrated and returns to normal operation.
• If you enter Calibration Mode, Configuration Mode, or Gas Type Mode, the signal output will be fixed at 3.5
mA until the M2A returns to normal operation.
• If the M2A’s input power decreases below 9.5 volts so that the M2A is in a low power alarm, the signal
output is fixed below 2.4 mA until the low power alarm is cleared.
• If the M2 goes into a fail condition, after a 30 second delay, the signal output is fixed below 2.4 mA until the
fail alarm is cleared. During the 30 second delay, the signal output follows the detector output. In the case of
a downscale reading, the display and the signal output continue to track the reading down to -99% of full
scale (1.15 mA).