RKI Instruments 65-2649RK-CH4-4 User Manual

65-2649RK-CH4-4

M2A Transmitter

Operator’s Manual

Part Number: 71-0318RK

Revision: P1

Released: 5/16/14

RKI Instruments, Inc.

www.rkiinstruments.com

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 6 and 12 months, but can be required more
often or less often based on your usage.

65-2649RK-CH4-4 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 fr o m date of shipment
from RKI Instruments, Inc. Any parts found defective withi n tha t 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 ser v ice, and
which must be cleaned, repaired, or replaced on a routine basis. Examples of such items
are:

W arranty 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 , a nd we are not r esponsible for removal or r eplacement costs,
local repair costs, transportation costs, or contingent expenses incurred without our prior
approval.

a) Absorbent cartridges d) Batteries
b) Pump diaphragms and valves e) Filter elements
c) Fuses

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 indemnificatio n f o r any accident or da ma g e c au sed by the operat io n of
this gas monitor, and our warranty is limited to the replacement of parts or our complete
goods.

65-2649RK-CH4-4 M2A Transmitte r Op erato r’ s Manu al

Table of Contents

Chapter 1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

About the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

About this Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Chapter 2: Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

External Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Internal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Chapter 3: Installation & Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Mounting the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Wiring the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Chapter 4: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Information Screen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4 - 20 mA Signal Output Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Alarm Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Chapter 5: Configuration Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Viewing & Changing M2A Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Chapter 6: Gas Type Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Selecting the Gas Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Chapter 7: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Calibration Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Determining Response Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Replacing the IR LEL Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Chapter 8: RS-485 Modbus Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Wiring the M2A in a Modbus System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Using the M2A in a 4-wire Modbus System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Modbus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Supported Modbus Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Appendix A: Control Button Quick Reference Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Appendix B: PLC and DCS Device Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Appendix C: Function Code 16 Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

(Appendix C available from RKI Instruments, Inc. Not included in manual as normally
provided with M2A detector head.)

65-2649RK-CH4-4 M2A Transmitte r Op erato r’ s Manu al

Chapter 1: Introduction

Overview

This chapter briefly describes the 65-2649RK-CH4-4 M2A Transmitter. This chapter also
describes the 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual (this document).
Table 1 at the end of this chapter lists the specifications for the M2A.

About the M2A Transmi tter

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 OL E D d isplay which is visible through
the window in the cover (front face) and provides a 4 - 20 mA sign al which indicates the
target gas reading for use by a gas monitoring controller, recording device, or
programmable controller. The M2A also pro vides an RS- 485 Mo dbus output. Thr ee 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 info rmation.

CAUTION: Describes pote ntial damage to equip ment.

WARNING: Describes potential danger that can result in injury or death.

1 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Specifications

Table 1 lists specifications for the M2A.

Table 1: M2A Specifications

Target Gas/Detection Range Methane: 0 - 100% LEL, 1% LEL increments
Alarm Settings (Alarm 1/Alarm 2) 10 %LEL/50 %LEL
Construction (housing) Explosion-proof Junction Box, NEMA 4
Area Classific ati on Explosion-pr oo f 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 5.5 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

• RS-485 Modbus
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

“Vi ew ing & Changi n g M2A Para mete rs” on page 22.

WARNING: When using the M2A, you must follow the instructions and war ni ngs in

this manual to assure proper and safe operation of the M 2A and to
minimize the risk of personal injury. Be sure to maintain and periodically
calibrate the M2A as described in this manual.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 2

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 IR LEL detector, calibration adapter/splash
guard, terminal PCB, the M2A junction box, and the detector junction box. The two
junction box configuration is in tended 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.

Mounting Slot (2x)

Magnetic
Wand

Window

3/4" N PT C onduit

Hu b, Pl ugged

3/4" N PT

Conduit Hub

3/4" NPT Conduit Hub

Terminal
Strip

M2A

Junction

Detector

Junction Box

Box

IR LEL D ete ctor

3/ 4" NP T
Conduit Hub

Calibration Adapter/

Sp lash Gua rd

Figure 1: M2A External Components

3 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

M2A Junction Box

The M2A’ s cast aluminum junction box protects the terminal PCB and wiring connections
made to the terminal PCB. Use the three 3/4 in. conduit hubs to wire the remotely installed IR

LEL detector and connect wiring from an external device, typ ically an RKI co ntroller. 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 e nsure

water does not enter the junction box. See “Wiring the M2A Transmitter” on
page 11 for complete wiring instructions.

Use the junction box’s two mounting slots 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 IR LEL 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” conduit hub. Three spacers installed on the back of the junction box controls
the distance of the junction box from a mounting surface.

Infrared LEL Detector

The infrared LEL detector is made up of a miniature infrared combustible gas LEL
detector housed and encapsulated in a pipe nipple. The pipe nipple has 3/4” NPT thr eads
on each end and a 1 1/4” hex that allows removal or installation of the detector with a
wrench. A por ous flame arr e stor t hat is coat ed wit h a hydr o phobic f ilm that re pels liquids
is on one end of the detector and al lows samp le gas to enter the detector. Four color coded
leads, red, white, green, and black, extend from the other end of the detector. The leads
allow you to connect the detector to the terminal strip.

Calibration Adapter/Splash Guard

A calibration adapter/splash guard is installed on the IR LEL 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.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 4

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.

3/4" NPT Conduit Opening, Plugged

Power/Signal

Terminal Strip

Detector Terminal Strip

(Comb/CO2 Version Shown)

Detector Current

(Comb/CO2 TypeOnly,

Adjust Pot

Factory Adjust)

3/4" NPT

Conduit

Opening

forWire

Entry

Ground Jumper

Programming

Connector

(Factory Use)

Modbus Terminal Strip

Termination Jumper

Ribbon Cable Connector

Fail LED

Alarm 1 LED

Alarm 2 LED

RX LED

TX LED

Relay
Terminal
Strips

Junction Box

Terminal PCB

Control PCB

Magnetic
Switches

ENTER

DOWN/NO

- S +

LEL

R W G B

RS 485 PWR/SIG

A B C

FAIL

C NC NO

ALARM 1

C NC NO

ALARM 2

C NC NO

UP/YES

Push Button

Control

NO

RKI INSTRUMENTS

M2A TRANSMITTER

Switches

UP/YES

DOWN/NO

ENTER

OLEDDisplay

View With Cover and

Control PCB Remo ved

View With Cover Removed

Figure 2: M2A Internal Comp onents

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. A factory adjust pot
just above the programming connector is used to set the detector current.

5 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Power/Sign al 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. All four terminals are used to connect the
detector to the M2A.

Detector

Terminal

Strip

- S +

LEL

R W G B

RS 485 PWR/SIG

A B C

C NC NO

C NC NO

C NC NO

FAIL

ALARM 1

ALARM 2

Figure 3: Detect o r Term inal Strip

NOTE: The detector is factory-wired to the M2A. See “Wiring the M2A T ransmitter” on

page 11 for all wiring procedures related to M2 A.

Modbus Terminal Str ip

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 in to 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. The y are three-positio n 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. Leave this jumper installed unless directed to remove it for a Modbus

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 6

installation. See “Chapter 8: RS-485 Modbus Output” on page 36 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 36 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 th e ban an a j ack s 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, an d save changes to the settings.
The push button switches are located along the bottom edge of the control PCB (see
Figure 2). The UP/YES button is on the left, the DOWN/NO button is in the middle, and
the ENTER button is on the right.

Table 2: M2A Control Button Functions

Switch Function

UP (YES) • Saves settings

• Changes the displayed set t ing

• Enters th e Calibration Program

• Enters Gas Type Mode (press with DOWN/NO button)

• Enters Configuration Mode (pres s with EN TER button )

DOWN (NO) • Cancels setting changes

• Changes the displayed set t ing

• 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 w ith DOW N /NO button)

• Functions as an alarm reset switc h

Just above each push button switch is a magnetic switch with the same function as th e
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 17).

7 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Status LEDs

The M2A includes five status LEDs that are located above the display (see Figure 2).

• 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.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 8

Chapter 3: Installation & Startup

b

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 a ccessible.

• 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.

5.86

• 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 4 shows the outline and mountin g
dimensions the M2A junction box. Figure 5 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 5.

4.59

2.41

5.23

5.00

3/4 NPT
Conduit Hu

1.02
.47 (2X)

Figure 4: Outline & Mounting Dimensions, M2A Junction Box

9 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

.30 (2X)

r

,

3/4 N PT

Female

3.65

9.00 MAX

2.70 .38

Rubb e
Spacer
3X

J-Box

IR LE L

Detec tor

5.25
Calibration

Adapt er/

Splash Guar d

.75

Figure 5: Outline & Mounting Dimensions, Detector Junction Box

3. Install 3/16 inch I.D. flexible po lyurethane tubing to the fitting at the bottom of the
calibration adapter/splash guard and route it to an accessible area that is close to the
M2A junction box. See the “Parts List” on page 46 for available tubing.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 10

Wiring the M2A Transmitter

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. Guide a four conductor shielded cable or four 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, white, green, and black.

NOTE: Consult RKI Instruments, Inc. for cable lengths longer than 200 feet.

8. Connect the detector leads to the terminal block in the detector junction box.

9. Secure the detector junction box’s cover to the junction box.

10. Guide the other end of the four-conductor, shielded cable or four wires in conduit
through the bottom conduit hub of the M2A junction box.

11. To gain access to a plug-in termina l 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 th e alarm 1 r elay t ermi nal strip ma y be r emo ved
by grasping them with your fingers if the adjacent terminal strips have been removed.

WARNING: If the M 2A 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 4
environmental rating of the junction box and avoid water entering the
junction box at the conduit hubs.

11 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

12. Pull out the detector terminal strip and connect the four wires to the terminal strip as
follows (see Figure 6).

• Connect the wire corresponding to the detector ’s red wire to the LEL “R”

terminal.

• Connect the wire corresponding to the detector’s white wire to the LEL “W”

terminal.

• Connect the wire corresponding to the detector’s green wire to the LEL “G”

terminal.

• Connect the wire corresponding to the detector’s black wire to the LEL “B”

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.

Cable

Shield

Detector

Terminal

Strip

- S +

LEL

R W G B

RS 485 PWR/SIG

A B C

FAIL

C NC NO

ALARM 1

C NC NO

ALARM 2

C NC NO

Black
Green
White
Red

Black
M2A
J-Box

Green

White

Red

Detector J-Box

IR LEL Detector

Calibration Adapter/Splash Guard

Figure 6: Wiring the Detector to the M2A

13. Reinstall the detector terminal strip into its socket.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 12

14. 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.

15. Guide multi conductor shielded cable or cables or wires in conduit through the side
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 se a l the threads to

ensure water does not enter the junction box. A conduit seal, wh i c h is
normally required to maintain the junction b ox’s hazardous location
rating, will also help to prevent water from entering through the top port.

NOTE: If the M2A is being wired to a PLC or DCS device, see “Appendix B: PLC and

DCS Device Wiring” on page 48, 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 connect to th e S termi na l to
access this signal, the M2A will still function completely.

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.

• 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 cabl e 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 “Cha pter 8: RS-485 Modbus

Output” on page 36.

13 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

RKI Controller

Terminals

See Figure 7 below for field wiring connections to the M2A.

Alarm Device

Cable Shield

Power

(24 VDC) +

4 - 20 mA In (S)

(24 VDC) -

Fail
Alarm
Device

Alarm 1
Alarm
Device

Alarm 2
Alarm
Device

See

Detector

Wiring

See

Modbus

Wiring

- S +

LEL

R W G B

RS 485 PWR/SIG

A B C

FAIL

C NC NO

ALARM 1

C NC NO

ALARM 2

C NC NO

Typical Alarm
Wiring Shown

Figure 7: Wiring the M2A Junction Box to a Controller and Alarm Devices

16. Re-install the control PCB (and ribbon cable if necessary) . B e 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.

17. Secure the M2A junction box cover to the junction box.

18. Make controller, 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 gas mon itoring controller, recording device, or
program mable controller.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 14

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 necessar y, turn on the controller or ot her monitoring 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. V erify that the display is indicating the target gas and current gas reading
after the warm-up period is complete and normal operation begins.

METHANE

0 %LEL

NOTE: Allow the M2A’s detector to warm up for 15 minutes before you continue with

the next section, “Adjusting the Fresh Air Reading.”

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
combustible or toxic gas vapors and of normal oxygen content, 20.9%).

CAUTION: If you suspect the presence of combustible gas in the monit oring 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 “Calibration” on page 32
for instructions on ho w 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.

15 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

WARNING: The M2A i s not an active gas monitoring device during the fresh air

adjustment procedure. The 4-20 mA output signal will “freeze” at 3.5 mA
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 22 for instructions to chang e
the calibration time-out.

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.

Calib?
YES/NO

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 di splay 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.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 16

Chapter 4: Operation

Overview

This chapter describes the M2A in normal operation. This chapter also describes the M2A
in alarm 1, alarm 2, and fa il 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.

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 5.0 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
v5.0L 2A

17 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

4 - 20 mA Signal Output Operation

The output at the S terminal of the power/signal terminal s t rip is a 4 - 20 mA signal t hat
corresponds to the detection range of the M2A. During normal operation, this signal
tracks the gas concentration on the OLED display.

There are several cir cumstances where th e 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 3.5 mA
(zero).

• 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 cont inue 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 operat ion.

• If you enter Calibration Mode, Configuration Mode, Gas Type Mode, or Modbus
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 18.5 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 M2A 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).

Alarm Indications

NOTE: The M2A includes alarm on and alarm off delay settings for alarm 1 and alarm

Condition Cause Visual Indication(s)

Alarm 1

Alarm 2

1

1

2. The alarm indications described in this section operate according to the
factory set alarm settings. See Table 5 on page 23 for all the factory settings.

Table 4: Visual and Audible Alarm Indications

Increasing gas reading at or above the
alarm 1 setpoint

Increasing gas reading at or above the
alarm 2 setpoint

• A1 LED is on

• Gas reading alternates

with ALARM-1 message

• A2 LED is on

• Gas reading alternates

with ALARM-2 message

Fail • Disconnected or misconnected

detector wiring

• Display reading at -10% of full
scale or lower

• Defective components

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 18

• F LED is on

• FAIL message replaces

gas reading

NOTE: There is a 30 second
delay on the fail condition.

Table 4: Visual and Audible Alarm Indications

Condition Cause Visual Indication(s)

Low Power DC power source less than 9.5 volts. • F LED is on

• LowPower message and

actual voltage of
incoming DC power

*1If the M2A is in both an alarm 1 and an alarm 2 condition, both alarm LEDs are on and

the display alternates between the gas reading and the ALMS 1&2 message.

NOTE: You can select normally energized (N. EN) or normally de-energized (N. DE-

EN) alarm 1 and alarm 2 relay set tings in Configuration Mo d e. The following
sections describe the standard factory setting for these relays which is
N. DE-EN.

The fail relay is factory set as N. EN and is not user-adjustable.

Alarm 1 Condition

Alarm 1 Condition Indications

When the gas read ing reaches the alarm 1 setpoint, the M2A senses an alarm 1 condition.
The M2A alerts you to an alarm 1 condition as follows:

• The A1 LED turns on.

• The gas reading alternates with the ALARM-1 messag e.

• The alarm 1 relay energizes.

Responding to an Alarm 1 Condition

1. Follow your established procedure for a low level combustible gas condition.

2. After the gas reading falls below the alarm 1 setpoint, press the ENTER button to reset
the alarm 1 circ uit. Re setti ng th e alarm 1 ci r cuit turns off the A1 LED, resets the OLED
display, and de-energizes the alarm 1 relay.

NOTE: If the ENTER button is pressed while the M2A is in an ala rm 1 condition, the

A1 LED will flash but all other i nd ications will remain unchanged.

You cannot de-energize the al arm 1 relay until the gas reading falls below the
alarm 1 setpoint.

Alarm 2 Condition

Alarm 2 Condition Indications

When the gas read ing reaches the alarm 2 setpoint, the M2A senses an alarm 2 condition.
The M2A alerts you to an alarm 2 condition as follows:

• The A2 LED turns on.

• The gas reading alternates with the ALARM-2 messag e.

• The alarm 2 relay energizes.

19 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

NOTE: If the M2A is in bo t h an alarm 1 a nd alarm 2 condition, both the A1 and A2

LEDs will be on, the gas reading will alternate with the ALMS 1&2 message,
and both alarm relays will energize.

Responding to an Alarm 2 Condition

1. Follow your established procedure for a high level combustible gas condition.

2. After the gas reading falls below the alarm 2 setpoint, press the ENTER button to reset
the alarm circuit. Resetting the alarm circuit turns off the A2 light, resets the OLED
display, and de-energizes the alarm 2 relay.

NOTE: If the ENTER button is pressed while the M2A is in an ala rm 2 condition, the

A2 LED will flash but all other i nd ications will remain unchanged.

You cannot de-energize the al arm 2 relay until the gas reading falls below the
alarm 2 setpoint.

Fail Condition

Fail Condition Indications

The M2A indicates a fail condition f or any of the following:

• The detector wiring is disconnected or incorrectly connected.

• The display reading is -10% of full scale or lower.

When the M2A senses a fail condition, it alerts you as follows:

• The F LED turns on.

• The gas reading is replaced by the FAIL message.

• The fail relay de-energizes.

NOTE: The fail alarm has a 30 second delay.

Responding to a Fail Condition

1. Verify that the detector wiring is correctly and securely connected.

Low Power Alarm

Low Power Alarm Indications

The M2A senses a low power condition when the DC power source is 9.5 volts or less.

WARNING: While in a low power condition, the M2A is not an active gas monitor.

When the M2A senses a low power condit ion, it alerts you as follows:

• The F LED turns on.

•The message LowPower is indicated on the top line of the OLED display and the
input voltage is displayed on the bottom line of the OLED display.

• The fail relay de-energizes.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 20

NOTE: The low power alarm canno t be cl eared using the ENTER button.

When the voltage increases to 10.0 volts, the low power alarm is cleared and the M2A will
begin its warm-up sequence.

Responding to a Low Power Condition

1. Determine and correct the cause of the low power condition.

2. When the input power increases above 10.0 volts, the M2A will begin its warm-up
sequence.

3. Verify that the M2A enters normal operation after its warm-up sequence. If necessary,
perform a fresh air adjustment. See “Adjusting the Fresh Air Reading” on page 15.

21 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Chapter 5: Configuration Mode

Overview

This chapter describes how to view and change M2A parameters using Configuration
Mode. It is accessed using the program buttons.

Configuration Mode includes a 5-minute time-out feature. If you do not press a control
button for 5 minutes, the M2A automatically returns to normal operation.

NOTE: If the M2A returns to normal operation because of a time-out, it enters a warm-

up period just as it does when it is first turned on.

If you are installing a new M2A, it has been setup at the factory. Use
Configuration Mode only if you wa nt to change the M2A’s setup. If you want
to change the detector type see “Chapter 6: Gas Type Mode” on page 25.

Viewing & Changing M2A Parameters

1. While in normal operation , simultaneously press and hold the UP/YES and ENTER
buttons for 5 seconds to enter Configuration Mode. Release the buttons wh en the
following screen appears.

Enter
Config?

2. If you want to exi t Config uration M ode, pr ess and r eleas e the DOWN/N O button an d
the M2A will return to normal operation.

If you want to continue in Configuration Mode, press and release the UP/YES button.
The target gas and the full scale will be displayed for a few seconds b efo re the first
adjustable par ameter, the alarm 1 setpoint, is displayed.

3. If you want to change the currently displayed parameter, use the UP/YES and
DOWN/NO buttons to adjust it to the desired setting, then press ENTER to continue
to the next parameter.

If the currently displayed parameter is OK, press the ENTER button to proceed to the
next parameter.

Table 5 lists the M2A parameters you can set. Table 5 also lists the factory set value for
each parameter.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 22

Table 5: Configuration Parameters

Parameter

(Factory Set Value)

ALARM-1 (level)
(10% LEL)

ALARM-1 (activation)
(Increase)

ALARM-1 (relay action)
(N. DE-EN)

ALARM-1 (relay reset)
(LATCH)

A1 OnDy (alarm 1 on delay)
(1 secs)

A1 OffDy (alarm 1 off delay)
(0 sec.)

Description

The gas reading at which the M2A initiates an alarm 1 condition.

Indicates if the alarm 1 circuit is activated by gas readings increasing
(

Increase) or decreasing (Decrease) to the ALARM-1 Level.

If set as
and energizes when an alarm 1 condition is initiated.
If set as
de-energizes when an alarm 1 cond iti on is initia ted .

If set as
circuit after the alarm 1 condition passes.
If set as
the alarm 1 condition passes.

The amount of time the M2 A delay s a cti va tio n of t he a lar m 1 circui t on ce
an alarm 1 condition is initiated. It can be set in 1 second increments
from 0 - 60 seconds, in 1 minute increments from 1 - 15 minutes, and in
15 minute increments from 15 - 60 minutes.

The amount of ti me the M 2A delay s turning off the alarm 1 circuit once an
alarm 1 condition passes. This parameter appears only if the alarm 1
relay reset setting is set to
increments from 0 - 60 seconds, in 1 minute increments from 1 - 15
minutes, and in 15 minute increments from 15 - 60 minutes.

N. DE-EN, the alarm 1 relay is de-energized in normal operatio n
N. EN, the alarm 1 relay is energized in normal operation and

LATCH, you must press the ENTER button to reset the alarm 1

SELF-RST, the M2A automatica lly reset s the a larm 1 circu it afte r

SELF-RST. It can be set in 1 second

ALARM-2 (level)
(50% LEL)

ALARM-2 (activation)
(Increase)

ALARM-2 (relay action)
(N. DE-EN)

ALARM-2 (relay reset)
(LATCH)

A2 OnDy (alarm 2 on delay)
(1 secs)

A2 OffDy (alarm 2 off delay)
(0 sec.)

The gas reading at which the M2A initiates an alarm 2 condition.

Indicates if the alarm 2 circuit is activated by gas readings increasing
(

Increase) or decreasing (Decrease) to the ALARM-1 Level.

If set as
and energizes when an alarm 2 condition is initiated.
If set as
de-energizes when an alarm 2 cond iti on is initia ted .

If set as
circuit after the alarm 2 condition passes.
If set as
the alarm 2 condition passes.

The amount of time the M2 A delay s a cti va tio n of t he a lar m 2 circui t on ce
an alarm 2 condition is initiated. It can be set in 1 second increments
from 0 - 60 seconds, in 1 minute increments from 1 - 15 minutes, and in
15 minute increments from 15 - 60 minutes.

The amount of ti me the M 2A delay s turning off the alarm 2 circuit once an
alarm 2 condition passes. This parameter appears only if the alarm 2
relay reset setting is set to
increments from 0 - 60 seconds, in 1 minute increments from 1 - 15
minutes, and in 15 minute increments from 15 - 60 minutes.

N. DE-EN, the alarm 2 relay is de-energized in normal operatio n
N. EN, the alarm 2 relay is energized in normal operation and

LATCH, you must press the ENTER button to reset the alarm 2

SELF-RST, the M2A automatica lly reset s the a larm 2 circu it afte r

SELF-RST. It can be set in 1 second

23 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Table 5: Configuration Parameters (Continued)

ZeroSupp
(2% LEL)

FILTER
(5 secs)

CAL Time
(15 mins)

Auto Zero
(Enabled)

Parameter

(Factory Set Value)

Description

The zero suppression feature helps prevent “jumpy” readings near the
fresh air reading.
For example, if the zero suppression is
reading of 0% LEL for gas readings from -2% LEL to 2% LEL. It is
settable from 0 to 6% of the detection range.

The filter feature helps “smooth out” jumpy or noisy signals from the
detector. You can set the filter from 0 seconds to 60 seconds in 5
seconds increments.
The displayed g as rea din g i s the a ve rage rea din g o ve r the pre vi ous time
period defined by the filter setting. So if the filter is set to 5 seconds, the
displayed gas reading is the average over the past 5 seconds.

The calibration t ime-out set s the am ount of ti me aft er the last bu tton push
while in Cali bration Mode that the M2A will wait before returning to
normal operation. If the calibration time-out is set to
will return to no rmal operation automatically 15 minutes after the last
button push.

If set to
reading and make automatic zero adjustments under precisely specified
conditions if it determ ine s tha t a reading ch ang e is du e to no rm al sens or
drift.
If set to

Enabled, the M2A’s firmware will monitor the zero (fresh air)

Disabled, the Auto Zero function is turned off.

2.0% LEL, the M2A wi ll displ ay a

15 mins, then M2A

4. When you have scrolled through all the adjustable parameters, SAVE IT? YES/NO
appears on th e display.

5. If you do not wish to save the adjustments and want to exit Configuration Mode,
press and release the DOWN/NO button. The DO OVER? YES/NO message will
display. Press and release the DOWN/NO button. The ABORT? YES/NO message
will display. Press the UP/YES button to return to normal operation.

If you wish to change some of the adjustments made, press and release the DOWN/
NO button. The DO OVER? YES/NO message will display. Press and release the UP/
YES button. The Re-do Config message will display and the M2A will return to the
first adjustable parameter. Go back to step 3 and continue.

If you wish to save the adjustments made, press and release the UP/YES button.
Config Saved is indicated on the display for a few second s and the M2A returns to
normal operation.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 24

Chapter 6: Gas Type Mode

Overview

This chapter describes how to use Gas Type Mode to select the M2A’s gas type. The gas
type determines the target gas and detection range.

CAUTION: The 65-2649RK-CH4-4 M2A is factory setup for methane (CH4). Do not change

the Gas Type setting.

Gas Type Mode includes a 5-minute time-out feature. If you do not press a button for 5
minutes, the M2A automatically returns to no rmal operation.

NOTE: If the M2A enters normal operation because of a program time-out, it enters a

warm-up period just as it does when it is first turned on.

Selecting the Gas Type

1. While in normal operation or d uring the warm-up sequence, press and hold the UP/
YES and DOWN/NO buttons for five seconds. Release them when the following
screen appears.

2. If you want to exit Gas Type Mode, press and release the DOWN/NO button. The
display will indicate NO CHANGE and the M2A will return to normal operation.

If you want to continue in Gas Type Mode, press and release the UP/YES button. The
top display line will indicate GasType? and the bottom display line will indicate the
target gas choice.

3. Use the UP/YES or DOWN/NO button to scroll through the choices of target gas.
Table 6 below lists the choices of target gas for the M2A.

HC 0 - 100% LEL
iBUTANE 0 - 100% LEL

Table 6: Gas Types

Gas Type

Choices

Select
GasType?

Detection Range

PROPANE 0 - 100% LEL
HEXANE 0 - 100% LEL
HYDROGEN 0 - 100% LEL
METHANE 0 - 100% Volume

25 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Table 6: Gas Types

Gas Type

Choices

Detection Range

METHANE 0 - 100% LEL
CO2 0 - 5,000 ppm
CO2 0 - 2,000 ppm
CO2 0 - 100% volume
CO2 0 - 50.0% volume
CO2 0 - 5.00% volume
NH3 0 - 5.00% volume
NH3 0 - 2.00% volume

4. When the desired target gas is on the display, press and release the ENTER button.
The display will ask SAVE IT? YES/NO.

5. To discard the gas type change, press and r elease th e DOWN/NO button. The display
will ask DO OVER? YES/NO. Press the DOWN/NO button. The display will ask
ABORT? YES/NO. Press the UP/YES button. The M2A will return to normal
operation without changing the gas type.

To save the gas type, press and release the UP/YES button. The display will indicate
Gas T ype Up dated, the display will indicate the target gas and the detection range for
a few seconds, and then the M2A will enter Configuration Mode automatically so that
the parameter settings in Configuration Mode can be verified or changed.

6. While in Configuration Mode press and release the ENTER button to accept the
displayed parameter setting and move to the next one. Use the UP/YES and DOWN/
NO buttons to adjust a s et tin g. See “Chapter 5: Configuration Mode” on pag e 22 for a
complete description of Configuration Mode.

7. When you have reviewed and accepted the last item in Configuration Mode by
pressing the ENTER button, display will ask SAVE IT? YES/NO.

8. To save the configuration settin gs, press and release the UP/YES button.The display
will indicate Config Saved and the M2A will begin its warm-up sequence.

To discard the settings and review them again, press the DOW N/NO button. The
display will ask DO OVER? YES/NO. Press the UP/YES button and the display will
indicate Re-do Config, then display the target gas and the detection range for a few
seconds before returning to Configuration Mode. Repeat steps 6 - 8 until the settings
are as desired.

9. After the M2A completes its warm-up sequence, the display will indicate CAL
NEEDED. Since the gas type has been changed, a successful calibration must be
performed before the M2A can enter normal operation.

10. Press and release the UP/YES button to enter Calibration Mode. Normally, you must
hold the UP/YES button for 5 seconds to enter Calibration Mode, but since a
calibration is required, only a momentary push is needed to enter Calibration Mode
after changing the gas type.

11. See “Calibration” on page 32 for calibration in structions.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 26

NOTE: When calibrating an M2A after changing the gas type, the M2A will not ask if

you want to calibrate, or whether you want to perform a fresh air adjustment,
span adjustment or zero adjustment. Since a complete calibration is required,
the calibration sequence will proceed without asking if you want to perform
certain operat ions.

27 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Chapter 7: Maintenance

Overview

This chapter describes procedures for performing preventive maintenance,
troubleshooting, calibrating the M2A, and replacing field replaceable parts.

Preventive Maintenance

This section describes a recommended preventive maintenance schedule to ensure the
optimum performance of the M2A. It includes daily, monthly, and biannual procedures.

Daily

Verify a display reading of 0% LE L. In vestigate significant changes in the reading.

Monthly

This procedure describes a test to verify that the M2A responds properly to the target gas.

NOTE: Performing a response test on the M2A may cause alarms. If you do not want

external alarms to act u ate, disable any external alarms duri ng the response test
to avoid unwanted external alarm indication s .

NOTE: The following procedure assumes the use of a calibration kit which includes a

calibration gas cylinder and a fixed flow regulator with an on/off knob.

1. Disable all external alarms if external alarm indications are not desired during the
response test.

2. Screw the calibration gas cylinder into the fixed flow regulator.

3. Use the flexible tubing coming from the calibration adapter/splash guard to connect
the regulator to the calibration adapter/splash guard.

4. Turn the regulator knob counterclockwise to open the regulator.

5. Allow calibration gas to flow for the length of time determined in “D et ermining
Response Time” on page 31.

6. Verify that the display reading is within ± 20% of the gas concentration .

NOTE: If the reading is not within ± 20% of the gas concentration, calibrate the M2A as

described in “Calibration” on page 32.

7. Turn the regulator knob clockw ise to close the regulator.

8. Unscrew the calibration gas cylinder from the fixed flow regulator.

9. Disconnect the calibration adapter/splash guard’s flexible tubing from the regulator.

NOTE: Do not disconnect the flexible tubing from the calibration adapter/splash guard.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 28

10. If external alarms have been disabled, enable them when the display returns to a
normal fresh air reading.

11. Store the components of the calibration kit in a safe place.

Biannually

Calibrate the M2A as described in “Calibration” on page 32. See “Calibration Frequency”
on page 31 for a discussion of calibration frequency guidelines.

Troubleshoo ting

The troubleshooting guide describes symptoms, probable causes, and recommended
action for problems you may encounter with the M2A.

NOTE: This troubleshooting guide describes M2A problems only. If the M2A is

connected to a controller, see the controller operator’s manual for problems you
may encounter with the controller.

Table 7:Troubleshooting the IR LEL Detector

Condition Symptom(s) Probable Causes Recommended Action

No Power The display backlight

is off and the display
screen is blank.

Frequent or
Suspect
Alarms

The M2A alerts you
to frequent or suspect
alarms while th e
fresh air readings
remain on zero.

• The power wiring is
disconnected or
misconnected.

• The display cable is
disconnected or
misconnected.

•The M2A is
experiencing false
readings due to RFI
or EMI.

• The detector wiring
is disconnected,
misconnected, or
intermittent.

1. Verify that the wiring to the
power source or controller is
correct and secure.

2. Verify that the ribbon cable
connecting the terminal PCB to
the control PCB is securely
installed. This ribbon cable plugs
into a connector on the top edge
of the control PCB and on the
bottom of the terminal PC B.

3. If the power difficulties continue,
contact RKI for further
instruction.

1. Verify that the M2A wiring is
properly shielded. See “Wiring
the M2A Transmitter” on page 11.

2. Verify that the detector wiring is
correct and secure.

3. Increase the alarm on delay
setting in Configuration Mode.

4. If the frequent or suspect alarm
difficulties continue, contact RKI
for further instruction.

29 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Table 7:Troubleshooting the IR LEL Detector (Continued)

Condition Symptom(s) Probable Causes Recommended Action

Flickering
Display

Fail
Condition

The display reading
flickers often.

• M2A indicates a
fail condition.

• Controller
indicates a fail
condition

•The M2A is
experiencing false
readings due to RFI
or EMI.

•The noise filter
setting is too low.

•The zero
suppression setting
is too low.

• The display screen
is malfunctioning.

• The detector wiring
to the terminal PCB
is disconnected or
misconnected.

•The wiring from the
M2A to the
controller is
disconnected or
misconnected.

• The detector fresh
air signal is low
enough to cause a
fail condition.

•The detector is
malfunctioning.

•The terminal or
display PCB is
malfunctioning.

1. Verify that the M2A wiring is
properly shielded. See “Wiring
the M2A Transmitter” on page 11.

2. Verify that the detector wiring is
correct and secure.

3. Increase the filter setting in
Configuration Mode.

4. Increase the zero suppression
setting in Configuration Mode.

5. If the display difficulties continue,
contact RKI for further
instruction.

1. Verify that the detector wiring is
correct and secure.

2. Verify that the wiring between the
M2A and the controller is correct
and secure.

3. Calibrate the M2A.

4. If the fail condition continues,
replace the detector.

5. If the fail condition continues,
contact RKI for further
instruction.

Slow or No
Response/
Difficult or
Unable to
Calibrate

•M2A responds
slowly or does not
respond to
response test.

•Unable to
successfu l ly set
the fresh air or
span reading
during
calibration.

•M2A requires
frequent
calibration.

Note: See “Calibration
Frequency” o n page 31 for
calibration frequenc y
guidelines.

• The calibration
cylinder is low, out­dated, or defective.

• The calibration gas
flow rate is too low.

• The calibration gas
is not an
appropriate
concentration.

•The detector is
malfunctioning.

• The terminal PCB is
malfunctioning.

• The flexible tubing
to the calibration
adapter/splash
guard has become
kinked, blocked, or
disconnected.

1. V erify that the calibration cylinder
contains an adequate supply of a
fresh test sample.

2. Verify that the regulator used for
calibration is a 0.5 LPM regulator.

3. Verify that the calibration gas
concentration is appropriate for
the transmitter. The concentration
should be in the detection range,
preferably about half of the
detection range.

4. Verify that the flexible tubing to
the calibration adapter/splash
guard is clear and connected to
the calibration adapter/splash
guard.

5. If the calibration/response
difficulties continue, replace the
detector.

6. If the calibration/response
difficulties continue, contact RKI
for further instruction.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 30

Calibration Frequency

Although there is no particular calibration frequency that is correct for all applications, a
calibration frequency of every 6 months is adequate for most infrared combustible gas
transmitter applications. Unless experience in a particular application dictates otherwise,
RKI Instruments, Inc. recommends a calibration frequency of every 6 months.

If an application is not very demanding, for example detection in a clean, temperature
controlled environment where calibration adjustments are minimal at calibration, then a
calibration frequency of every 9 to 12 months is adequate.

If an application is very demanding, for example if the environment is not well controlled,
then more frequent calibration than every 6 months may be necessary.

Determining Response Time

Since the detector junction box is installed remotely from the M2A, the response time of
the detector will depend on the length of flexible tubing th at is attached to the calibration
adapter/splash guard. To determine the response time based on the length of tubing
connected:

1. Place the M2A into its calibration mode or disable external alarms.

2. Note the current gas reading displayed at the M2A.

3. Screw the regulator into the calibration cylinder. Do not use a zero air cylinder for this
operation.

4. Use the flexible tubing coming from the calibration adapter/splash guard to connect
the regulator to the calibration adapter/splash guard.

5. Turn the regulator’s on/off knob counterclockwise to open the regulator. Gas will
begin to flow. Take note of the time or start a stopwatch.

6. When you first start to notice an increase in the gas reading, note how much time
passed between starting the gas flow and noticing a reading response.

7. Turn the regulator’s on/off knob clockwise to close the regulator.

8. Unscrew the regulator from the calibration cylind er.

9. Disconnect the calibration adapter/splash guard’s flexible tubing from the regulator.

NOTE: Do not disconnect the flexible tubing from the calibration adapter/splash guard.

10. Add 1 minute to the length of time determined in step 6. This is the response time for
the detector. When performing a response test, zero adjustment, or span adjustment,
gas must be applied for this length of tim e .

31 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Calibration

This section describes how to calibrate the M2A transmitter. It includes procedures to
prepare for calibration, enter Calibration Mode, adjust the fresh air (zero) setting, adjust
the span setting, and return to normal operation.

WARNING: The M2A is not an active gas monitoring device during the calibration

procedure. The 4-20 mA output signal will “freeze” at 3.5 mA 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: The following procedure assumes the use of a calibration kit which includes a

calibration gas cylinder, a zero air cylinder and a fixed flow regulator with an
on/off knob.

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. See
“Viewing & Changing M2A Parameters” on page 22 for instructions to set the
calibration time-out.

NOTE: The following procedure assumes that the target gas is present in a high

enough concentration to affect the fresh air (zero) reading. If a fresh air
environment can be verified, applying zero air to the detector is not necessary
when setting the zero (span for oxygen) reading.

Non-Intrusive Calibration

If the M2A is installed in a classified area and non-intrusive calibration 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 opera tion as pres sing a contr o l switch
button, touch the magnet in the end of the magnetic wand to the M2A’s glass cover
directly above 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.

Calibration Gas Response Memory Feature

The M2A has the capability to “remember” the detector’s response to the calibration gas
after the gas is removed from the detector during the fresh air and span adjustment
procedure. This feature enables one person to perform calibration if the detector is
mounted remotely from the M2A. When zero air is applied to the M2A during a fresh air
adjustment, the M2A will freeze the display reading at the lowest response and the M2A
will continue to display this reading and retain it in its memory until the fresh air
adjustment procedure is completed. When calibration gas is applied to the M2A during a
span adjustment, the M2A will freeze the display reading at the highest response to the
calibration gas. The calibration gas can then be removed and the M2A will continue to
display this reading and retain it in its memory until the spa n a d justment procedure is
completed.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 32

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.

Calib?

YES/NO

2. If you want to continue with calibration, press and release the UP/YES button. The
display will indicate the target gas and CAL Mode for a few seconds before showing
FreshAir Adjust?.

If you want to exit Calibration Mode, press and release the DOWN/NO button. The
M2A will indicate Leaving CAL Mode and the M2A will return to normal operation.

3. T o continue with adjusting the fresh air reading, 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 lin e.

To skip adjusting the fresh air reading, press and release the DOWN/NO button. The
display will indicate SP A N w/ C a l Gas?. Skip to the next section, “Adjusting the Span
Setting”.

4. Screw the zero air cylinder into the fixed flow regulator.

5. Use the flexible tubing coming from the calibration adapter/splash guard to connect
the regulator to the calibration adapter.

6. Turn the regulator knob counterclockwise to open the regulator.

7. Allow zero air to flow for the length of time determined in “Determining Response
Tim e” on page 31.

8. Turn the regulator knob clockw ise to close the regulator.

9. Unscrew the zero air cylinder from the fixed flow regulator. Leave the calibration
adapter/splash guard’s flexible tubing connected to the regulator. The M2A will
continue to display the minimum gas response on the display and retain the response
level in its memory.

10. Press and release the ENTER button. The M2A will perform a fresh air adjus tment
and the display will indicate SPAN w/Cal Gas?.

NOTE: If the fresh air adjustment fai ls, see “Troubleshoot ing ” on pag e 29 for

recommended actions.

Adjusting the Span Setting

1. If you want t o con tin ue w ith adj usti ng t he sp an se ttin g, pr es s an d r ele ase the UP/YE S
button. APPLY will alternate with SPAN Gas on the top display line and the current
gas reading will be on the bottom display line.

If you want to skip adjusting the span reading, press and release the DOWN/NO
button. The display will indicate Leaving Cal Mode and the M2A will return to
normal operation.

2. Screw the calibration gas cylinder into the fixed flow regulator.

3. Turn the regulator knob counterclockwise to open the regulator.

4. Allow calibration gas to flow for the length of time determined in “D et ermining

33 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Response Time” on page 31.

5. Turn the regulator knob clockwise to close it.

6. Unscrew the calibration gas cylinder from the fixed flow regulator. The M2A will
continue to display the maximum gas response on the display and retain the response
level in its memory.

7. Adjust the gas reading up or down to match the calibration gas cylinder concentration
by using the UP/YES and DOWN/NO buttons, then press and release the ENTER
button.

8. The M2A will perform a span operation. The di splay will indicate SPAN Gas PASS
for a few seconds, then indicate SPAN Gas SAVED before indicating Leaving CAL

Mode for a few seconds.

NOTE: If the span adjustment fails, see “Troubleshooting” on page 29 for

recommended actions.

9. The display will now alternate between the normal operation screen and the message
REMOVE CAL GAS for 1 minute. If the calibration gas has not been removed from
the detector, remove it now to avoid unwanted alarms.

During this 1 minute period, the signal output will remain fixed at 3.5 mA and the
relays will remain in their non-alarm state to avoid unwanted alarms while the
calibration gas clears from the detector. At the end of the 1 minute period, the
REMOVE CAL GAS message will stop appearing and the M2A will return to normal
operation.

10. Disconnect the calibration adapter/splash guard’s flexible tubing from the regulator.

NOTE: Do not disconnect the flexible tubing from the calibration adapter/splash guard.

11. Store the components of the calibration kit in a safe place.

Replacing the IR LEL Detector

1. Turn off or disconnect power to the M2A.

2. Remove the detector junction box cover.

3. Unscrew the calibration adapter/splash guard from the detector.

4. Disconnect the detector leads from the terminal block in the detector junction box.
Note the position of the color-coded leads as you remove them.

5. Unscrew the detector from the detector junction box.

6. Guide the detector leads of the replacement detector through the bottom conduit hub
of the detector junction box, then screw the mounting threads of the detector into the
conduit hub. If necessary for environmental conditions, apply thread s eal an t o r t eflon
tape to the hub and/or detector threads to seal them.

7. Connect the detector leads to the terminal block the same way the old detector was
wired (see Figure 6 on page 12).

8. Screw the calibration adapter/splash guard onto the new detector.

9. Reinstall t he detector junct ion box cover.

10. Turn on or plug in power to th e M2A.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 34

NOTE: Allow the replacement detector to warm up for 15 minutes before you continue

with the next step.

11. Calibrate the replacement detector as described in “Calibration” on page 32.

35 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Chapter 8: RS-485 Modbus Output

Overview

This chapter describes the M2A’s RS-485 Modbus output and how to configure the M2A
to make use of it. It also discusses how to wire the M2A into a Modbus system.

The M2A provides an RS-485 serial communications interface. It is a Modbus Slave
Device, supporting 2-wire RS-485 Modbus RTU serial communications.

Wiring the M2A in a Modbus System

The M2A is a 2-wire Modbus RTU device. When wiring the M2A into a Modbus system,
adhere to standard Modbus wiring practices per the Modbus Over Serial Line
Specifica tio n a nd I mpl eme nt ati on Gu id e V1 .0 or la te r. This do cum en t can b e foun d on lin e
at www.modbus.org/specs.php.

The Modbus protocol supports a maximum of 247 unique slave addresses (1-247). The
M2A’s line driver provides for up to 128 M2As to be connected together without the need
for a repeater . Figure 10 & Figure 11 below illustrate typical M2A wiring configurations. If
more than 128 M2As need to be connected together, RS-485 repeater(s) should be used
such that no more than 128 M2As reside on any given network segment.

CAUTION: The network segment can only support 128 units if RKI M2As are being used. The

use of any other instruments will lower the number of units that may reside on any
given network segment.

The MODBUS terminal strip is located on the terminal PCB (see Figure 2). The following
signals are available at the Modbus terminal strip:

Table 8: Modbus Terminal Strip Signals

Modbus T erminal Label (RS-485

Name)

AD0
BD1
CCommon

Modbus Signal Name

Ground Jumper

The M2A includes a 2-pin ground header (see Figure 2) that is used when the M2A is used
in a Modbus system. Every M2A is supplied with a ground jumper (a jumper block)
installed onto this header. If the M2A isn’t wired into a Modbus system or if it is wired
into one as shown in Figure 9, the ground jumper should be installed. If the M2A is wired
in a Modbus system as shown in Figure 8, the ground jumper sho uld be removed.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 36

Recommended Modbus Wiring

The recommended Modbus wiring for the M2A is illustrated in Figure 8 below. In this
configuration, 5 wires are used for wiring the M2A into a Modbus system. Figure 8 also
illustrates typical alarm device wiring. The ground jumper must be removed in this wiring

configuration.

Power Supply

10-30 VDC

Remove Ground Jumper

Input

Terminals

Modbus Controller

+

-

Common

D1
D0

FAIL

C NC N O

ALARM 1

C NC N O

ALARM 2

C NC N O

See

Detector

Wiring

- S +

LEL

R W G B

RS 485 PWR/SIG

A B C

Figure 8: Recommended Modbus Wiring

See

Detector

Wiring

- S +

LEL

R W G B

RS 485 PWR/SIG

A B C

FAIL

C NC N O

ALARM 1

C NC N O

ALARM 2

C NC N O

To

Additional

M2As

Power Supply

10-30 VDC

Input

Terminals

Adding an M2A to an Existing M2 Modbus Installation with Recommended Wiring

An M2A can be wired into an existing M2 Modbus system. The shape of the terminal PCB
will be different but the wiring connections are identical and the ground jumper on the
M2A must still be removed.

Alternate Modbus Wiring For Existing Installations

Although the wiring shown in Figure 8 is recommended, it is possible to wire the M2A
into a Modbus system with only 4 wires in situations where a pre-existing system is being
replaced and wiring is already in place. This should only be done if wi ring for a system
that is being replaced is already installed and it is not practical to run another wire. See
Figure 9 below for this wiring configuration. In this configuration, the wire between the
“C” terminal on the M2A and the Common terminal on the Modbus controller is omitted.
Instead, the Common terminal on the Modbus controller is connected to the “-” of the 24
VDC power supply. The ground jumper must be installed in this wiring configuration.

Common

D1
D0

+

-

See

Detector

Wiring

- S +

LEL

R W G B

RS 485 PWR/SIG

A B C

FAIL

C NC NO

See

ALARM 1

C NC NO

ALARM 2

C NC NO

Detector

Wiring

- S +

LEL

R W G B

RS 485 PWR/SIG

A B C

FAIL

C NC NO

ALARM 1

C NC NO

ALARM 2

C NC NO

To

Additional

M2As

Modbus Controller

Figure 9: Alternate Modbus Wirin g

37 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

5

M2A

Termination

Jumper

Installed

Adding an M2A to an Existing M2 Modbus Installation with Alternate Wiring

An M2A can be wired into an existing M2 Modbus system. The shape of the terminal PCB
will be different but the wiring connections are identical and the ground jumper on the
M2A must still remain installed.

Termination Jumper

The M2A includes a 2-pin termination header (see Figure 2) that is used when the M2A is
used in a Modbus system. Every M2A is supplied with a termination jumper (a jumper
block) installed onto this header. If the M2A is not used in a Modbus system, this jumper
has no function. When the M2A is in stalled in a Modbus system, this jumper mus t be
installed in an M2A that is at the end of a Modbus line. Any M2A in a Modbus system that
is not at the end of a line must have the termination jumper removed (see Figure 10 &
Figure 11 below).

Modbus

Master

RS-485 RS-48

M2A

Termination

Jumper

Not Installed

ID = 1

M2A

Termination

Jumper

Installed

RS-485

M2A

Termination

Jumper

Not Install ed

Up to128 M2Ascan be conn ected withouta repeater

M2A

Termination

Jumper

Not Installed

ID = 126ID = 127

Figure 10: Multiple M2As in a Daisy Chain Configuration

Modbus

Master

M2A

Termination

Jumper

Not Instal led

M2A

Termination

Jumper

Not Installed

ID = 125

M2A

Termination

Jumper

Not Instal led

M2A

Termination

Jumper

Not Installed

ID = 1

ID = 128

M2A

Termination

Jumper

Installed

RS-485

M2A

Termination

Jumper

Not Installed

ID = 2 ID = 3

Up to 128 M2As can be connected without a repeater

Figure 11: Multiple M2As in a Two Branch Configuration

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 38

ID = 4

ID = 127

Using the M2A in a 4-wire Modbus System

Although the M2A is a 2-wire Modbus RTU device, it can be used with a 4-wire Modbus
controller if the system wiring is modified as follows:

• Connect the controller’s TxD0 and RxD0 wires together and use this connection as the
2-wire Modbus D0 signal.

• Connect the controller’s TxD1 and RxD1 wires together and use this connection as the
2-wire Modbus D1 signal.

• Connect these D0 and D1 signals and the common wire from the controller to the 2­wire Modbus Network of M2As.

Modbus Mode

Modbus Mode allows you to configure various parameters relating to the Modbus setup
of the M2A. Modbus Mode includes a 5-minute time-out feature. If you do not press a
control button for 5 minutes, the M2A automatically returns to normal operation .

NOTE: If the M2A returns to normal operation because of a time-out, it enters a warm-

up period just as it does when it is first turned on.

1. While in normal operation, simultaneously press and hold the DOW N /NO and
ENTER buttons for 5 seconds to enter Modbus Mode. Release the buttons when the
following screen appears.

Set Up
Modbus?

2. T o exit Modbus Mode, pr ess and r elease the DOWN/NO button. The M2A will return
to normal o peration.

To continue in Modbus Mode, press and release the UP/YES button. The current
ENABLED/DISABLED setting will appear.

3. If you want to change the currently displayed parameter, use the UP/YES and
DOWN/NO buttons to adjust it to the desired setting, then press ENTER to continue
to the next parameter.

If the currently displayed parameter setting is OK, press the ENTER button to proceed
to the next parameter.

Table 9 lists the M2A Modbus Mode parameters you can set. Table 9 also lis ts the
factory set value for each parameter.

39 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Table 9: Configuration Parameters

Modbus Mode Parameter Available Settings & Description

Enabled/Disabled Can be set to ENABLED or DISABLED (factory setting).

Enables or disables the Modbus output.

Slave ID The Slave ID can be set to values from 1 (factory setting) to 247.

The M2A will only receive messages from the Master which are
addressed to this Slave ID (except for broadcast messages which
are received by all slaves).

Baud Rate Can be set to 1200, 2400, 4800, 9600 (factory setting), 14440, &

19200.
Parity EVEN (factory setting), ODD, NONE
Response Delay The response delay can be set from 0 (factory setting) to 20 mS.

This is an optional additional de lay inserted by the M2A prior to
returning a response message to the Master. It may be helpful in
some installations where the Master’s preparedness to receive
responses might be delayed.

4. When you have scrolled through all the adjustable parameters, SAVE IT? YES/NO

appears on th e display.

5. If you do not wish to save the adjustments, press and release the DOWN/NO button.

The DO OVER? YES/NO message will display. Press and release the DOWN/NO
button. The ABORT? YES/NO message will display. Press the UP/YES button to
return to normal operation.

If you wish to change some of the adjustments made, press and release the DOWN/
NO button. The DO OVER? YES/NO message will display. Press and release the UP/
YES button. The Re-do MB Setup message will display and the M2A will return to
the first adjustable parameter. Go back to step 3 and continue.

If you want to save the adjustments made, press and release the UP/YES button.
Modbus Saved is indicated on the display for a few seconds and the M2A returns to
normal operation.

NOTE: All M2As on a Modbus network must be configured with the same baud rate

and parity, and each M2A must have a unique slave ID. For an M2A to
participate on a network, the ENABLED/DISABLED setting must be set to
ENABLE.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 40

Supported Modbus Functions

The M2A supports Function Code 03: Read Holding Registers and Function Code 16:
Write Registers.

Function Code 03: Read Holding Registers

There are a total of 40 registers available to be read via this Function Code.

Registers 1 - 2

The format (bit & field assignments) for registers 1 - 2 is shown below in Table 10 ­Table 11.

Table 10: Register 1, Numerical Reading with Sign & Decimal Point Bit & Field Assignments

Bit(s) Value & Field

[15] Sign of Reading

0 = Positive
1 = Negative

[14:13] Format of Reading

0 = XXX (no decimal point)
1 = XX.X
2 = X.XX
3 = .XXX

[12:0] Numerical value of display reading (8000 max)

Table 11: Register 2, Operating State, Alarms & Relays Bit & Field Assignments

Bit(s) Value

[15:12] Operating State

0 = Undefined
1 = Initialization
2 = Normal
3 = Warm -up
4 = Fail
5 = Calibration
6 = Post-Calibration
7 = Low Power
8 = Setup

[11] Gas Type Change

0=Not Changed
1=Changed

[10] Configuration Change

0=Not Changed
1=Changed

[9] Calibration Activity Flag

0=No Calibration Activity
1=Calibration Activity Has Occurred

41 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Table 11: Register 2, Operating State, Alarms & Relays Bit & Field Assignments (Continued)

Bit(s) Value

[8] Fail Status

0 = Fail Not As serted
1 = Fail Assert ed

[7:6] Alarm 2 Status

0 = No Alarm
1 = Unacknowle dged Alarm
2 = Acknowledged Alarm
3 = Unused Code

[5:4] Alarm 1 Status

0 = No Alarm
1 = Unacknowle dged Alarm
2 = Acknowledged Alarm
3 = Unused Code

[3] Overscale Status

0 = Not Overscale
1 = Overscale

[2] Fail Relay Status

0 = Not Energized
1 = Energized

[1] Alarm 2 Relay St atus

0 = Not Energized
1 = Energized

[0] Alarm 1 Relay St atus

0 = Not Energized
1 = Energized

Register 3

Register 3 is the supply voltage (0.1 volt per count).

Registers 4 - 11

The 16 bytes in these registers contain the same ASCII text information that is displayed
on the M2A’s OLED display (not NULL Terminated).

Register 12

Register 12 is the range (full scale readout).

Register 13

Register 13 is t he alarm 1 set point.
The decimal point location is the same as specified in Register 1.

Register 14

Register 14 is t he alarm 2 set point.
The decimal point location is the same as specified in Register 1.

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 42

Registers 15 - 19

Registers 15 - 19 are the Gas Name ASCII String (NULL Terminated).

Registers 20 - 22

Registers 20 - 22 are the Gas Units String (NULL Terminated).

Register 23

Register 23 is t he alarm 1 trigger.
0=Decreasing
1=Increasing

Register 24

Register 24 is the alarm 1 normal relay state.
0=Normally De-Energized
1=Normally Energized

Register 25

Register 25 is the alarm 1 relay reset.
0=Latching
1=Self-Resetting

Register 26

Register 26 is the alarm 1 ON delay.
Integer values are in seconds.

Register 27

Register 27 is the alarm 1 OFF dela y.
Integer values are in seconds.

Register 28

Register 28 is t he alarm 2 trigger.
0=Decreasing
1=Increasing

Register 29

Register 29 is the alarm 2 normal relay state.
0=Normally De-Energized
1=Normally Energized

Register 30

Register 30 is the alarm 2 relay reset.
0=Latching
1=Self-Resetting

Register 31

Register 31 is the alarm 2 ON delay.
Integer values are in seconds.

Register 32

Register 32 is the alarm 2 OFF dela y.
Integer values are in seconds.

43 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Register 33

Register 33 is zero suppression.
Toxics and LEL: 0%-6% of full scale
Oxygen: 0%-0.7% Oxygen
The decimal point location is the same as specified in Register 1.

Register 34

Register 34 is noise filter.
Integer values in seconds.
0-60 in 5 second increments.

Register 35

Register 35 is calibration timeout in minutes (5, 10, 15, 20, 25, or 30).

Register 36

Register 36 is calibration month (upper byte) and day (lower byte).
This is zero based (e.g. January=0 and the 1st=0).

Register 37

Register 37 is the calibration year.

Register 38

Register 38 is the calibration outcome.
Upper=Gas Operation
Lower=Air Operation

Calibration Outcome Codes:

1=Sensor Missing
2=Sensor Too Weak
3=Signal Too Strong
4=Not Enou gh Span
5=Negative Re ading
6=Span Gas Value Is Not OK
7=Calculated Zero Is Too Low
8=Calculated Zero Is Too High
9=Zero Failure
10=Span Failure
11=Calibration Is Overscale
12=LEL Sensor Offset Is Too High
13=LEL Null Operation Failed
14=Operat ion Not Performed

Register 39

Register 39 is the auto-zero disable.
0=AutoZero Enabled
1=AutoZero Disabled

Register 40

Register 40 is the remote configuration register access level
0=None
1=Alarm Reset

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 44

Function Code 16: Write Registers

There are 21 registers in Function Code 16 that can be used to write to the M2A. This
manual only describes Register 16 because it can be used to reset an al arm condition . For a
complete description of Function Code 16, request Appendix C from RKI Instruments,
Inc.

Register 16

Register 16 performs the same function as the ENTER button on the M2A. It is useful for
remotely silencing alarms. With the M2A in an alarm condit ion, bit [0] can b e used to
silence it.

Table 12: Register 16, Button Function

NOTE: Register 40 in Function Code 03, the remote configuration register, must be set

to 1 in order for Register 16 to work.

Bit Value & Field

[0] ENTER (used for “Alarm Reset”)

0=Not Pressed
1=Pressed

45 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Parts List

Table 13 lists replacement parts and accessories for the M2A Transmitter.

Table 13: Parts List

Part Number Description

06-1248RK Calibration kit sample tubing ( 3/16 in. x 5/16 in.; specify length

when ordering)
18-0400RK-01 Detector junction box, with spacers
18-0431RK-01 M2A junction box
45-6132RK Termination and ground jumper
61-0190RK-CH4 CH

71-0318RK 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual (this document)
81-0012RK-01 Calibration cylinder, 50% LEL methane in air, 34 liter steel
81-0012RK-03 Calibration cylinder, 50% LEL methane in air, 103 liter steel
81-0076RK-01 Zero air calibration cylinder, 34 liter steel
81-0076RK -03 Zero air calib ration cylinder, 103 liter steel
81-1050RK Regulator, with gauge and knob, 0.5 liter/minute continuous flow
81-1103RK-01 Calibration adapter/splash guard, with diffuser holes

LEL detector, IR type

4

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 46

Appendix A: Control Button Quick Reference Guide

The M2A’s cont rol buttons allow access to operational modes, resetting of alarms, and
display of the Information Screen. Table 14 shows which button combinations perform
these functions and which parameters are available for adjustment while in the
operational modes. While in these mo d es , di splay prompts showing a “?” require you to
respond by pressing either the UP/YES (for yes) or DOWN/NO (for no) button. To
change parameter settings, use the UP/YES and DOWN/NO buttons to get the desired
setting, then press and release the ENTER button to accept the setting.

Table 14: Control Button Quick Reference Chart

Mode Entered or

Function Performed

Alarm Reset Press and

Show Information
Screen

Calibration Mode Press and Hold

Configuration Mode Press and Hold

Gas Type Mode Press and Hold

Button

Combination

Release ENTER
Press and Hold

DOWN/NO

UP/YES for 5
seconds

UP/YES &
ENTER for 5
seconds

UP/YES and
DOWN/NO for
5 seconds

Adjustable or Viewable Parameters

n/a

•Input Voltage

• M2A Version/Revis ion Information

• Fresh Air Adjust

• Span (or Zero for Oxygen) Adjust with
Calibration Gas

• Alarm Levels

• Increasing or Decreasi ng Alarms

• Normally Energized or Normally De­energized Relays

• Latching or Self-resetting Alarms

• Alarm On Delay

• Alarm Off Delay (if self-resetting)

• Zero Suppression

• Noise Filter

• Calibration Time-out Period

Gas Type

Modbus Mode Press and Hold

DOWN/NO and
ENTER for 5
seconds

47 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

• Enable or Disable Modbus

•Slave ID

•Baud Rate

•Parity

• Response Delay

Appendix B: PLC and DCS Device Wiring

The M2A can be wired to a PLC or DCS device if desired.

1. Guide multi conductor shielded cable or cables or wires in conduit through the top
conduit hub of the junction box. The number of cables or wires needed will depend on
whether any relays are used and whether the Modbus output is used. Use the
following recommendations to determine how to wire the M2A:

• If Modbus connections will not be used and only the PWR/ SIG terminal strip

connections will be used, use four conductor shielded cable or four wires in
conduit for connections to the power/signal terminal strip.

Table 15: Wire Size for PWR/SIG Connections

Max Distance to Controller

w/18 Gauge Wire

2,500 ft. 5,000 ft. 8,000 ft.

• If the PWR/SIG terminal strip connections and one or more relays ar e used, route

the connections to the M2A in conduit. Use shielded cable in the conduit for the
PWR/SIG connections and unshielded cabl e 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 controller or device.

• If the M2A will be wired into a Modbus network, see “Cha pter 8: RS-485 Modbus

Output” on page 36.

Max Distance to Controller

w/16 Gauge Wire

Max Distance to Controller

w/14 Gauge Wire

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 48

24 VDC

Power Supply

24 VDC +

24 VDC -

See Figure 12 below for field wiring connections to the M2A.

Alarm Device

Power

4 - 20 mA In (S)

(24 VDC) -

Controller

(PLC, DCS)

- S +

FAIL

C NC NO

See

Detector

Wiring

See

Modbus

Wiring

R W G B

A B C

LEL

RS 485 PWR/SIG

C NC NO

C NC NO

ALARM 1

ALARM 2

Figure 12: PLC and DCS Device Wiring

Fail Alarm
Device

Alarm 1
Alarm Device

Alarm 2
Alarm Device

Typical Alarm

WiringShown

49 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Appendix C: Function Code 16 Registers

The M2A supports Function Code 16 that allows writing to the M2A. There are 21
registers in this Function Code.

Register 1

Register 1 is the alarm 1 set point.
Value must be an integer. Any decimals are omitted.

Register 2

Register 2 is the alarm 1 trigger.
0=Decreasing
1=Increasing

Register 3

Register 3 is the alarm 1 relay state.
0=Normally De-Energized
1=Normally Energized

Register 4

Register 4 is the alarm 1 relay reset.
0=Latching
1=Self-Resetting

Register 5

Register 5 is the alarm 1 ON delay.
Integer value is in seconds.

Register 6

Register 6 is the alarm 1 OFF delay.
Integer value is in seconds.

Register 7

Register 7 is the alarm 2 set point.
Value must be an integer. Any decimals are omitted.
The decimal point location is the same as specified in Register 1 of Function Code 03.

Register 8

Register 8 is the alarm 2 trigger.
0=Decreasing
1=Increasing

Register 9

Register 9 is the alarm 2 relay state.
0=Normally De-Energized
1=Normally Energized

Register 10

Register 10 is the alarm 2 relay reset.
0=Latching

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 50

1=Self-Resetting

Register 11

Register 11 is the alarm 2 ON delay.
Integer value is in seconds.

Register 12

Register 12 is the alarm 2 OFF dela y.
Integer value is in seconds.

Register 13

Register 13 is the zero suppression.
Toxics and LEL: 0%-6% Full Scale
Oxygen: 0%-0.7% Oxygen
Value must be an integer. Any decimals are omitted.

Register 14

Register 14 is the noise filter.
Integer value is in seconds (0-60 in 5 second increments).

Register 15

Register 15 is the calibration timeout.
Value is in minutes (5, 10, 15, 20, 25, or 30).

Register 16

Register 16 is explained in “Supported Modbus Functions” in the M2A manu al.

Register 17

Register 17 is the calibration month (MSB) and day (LSB).
This is zero-based (e.g. January=0 and the 1st=0).

Register 18

Register 18 is the calibration year.

51 65-2649RK-CH4-4 M2A Transmitter Operator’s Manual

Register 19

Register 19 is for cleari ng chang e flags. When parameters are changed at the M2A, a flag is
raised at the controller. This register can be used to clear those flags.

Table 16: Register 19, Clear Change Flags

Bit(s) Value & Field

[15:2] Unused
[1] Write “1” to this bit to clear “Gas Type Changed” flag
[0] Write “1” to this bit to clear “Configuration Changed” flag

Register 20

Register 20 is the AutoZero Disable.
0=AutoZero Enabled
1=AutoZero Disabled

Register 21

Register 21 is the Remote Configuration Regi ster.
0=No Remote Configuration
1=Reset Alarm

65-2649RK-CH4-4 M2A Transmitter Operator’s Manual 52