RKI Instruments M2 User Manual

M2 Transmitter

for 12 VDC Operation

Operator’s Manual

Part Number: 71-0115RK
Revision: H
Released: 4/3/14

RKI Instruments, Inc.

www.rkiinstruments.com

WARNING

Read and understand this instruction manual before
operating transmitter. Improper use of the transmitter
could result in bodily harm or death.

Periodic calibration and maintenance of the transmit ter
is essential for proper operation and correct readings.
Please calibrate and maintain this transm itter
regularly! Frequency of calibration depends upon the
type of use you have and the sensor types. Typical
calibration frequencies for most applications are
between 3 and 6 months, but can be required more
often or less often based on your usage.

M2 Transmitter Operator’s Manual, 12 V DC Operation

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 ge caused by the op e ration of
this gas monitor, and our warranty is limited to the replacement of parts or our complete
goods.

M2 Transmitter Operator’s Manual, 12 VDC Operation

Table of Contents

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

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

About the M2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

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

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

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

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

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

Internal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Chapter 3: Installation & Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Mounting the M2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Wiring the M2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Chapter 4: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Information Screen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4 - 20 mA Signal Output Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Alarm Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Chapter 5: Configuration Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

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

Viewing & Changing M2 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Chapter 6: Gas Type Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Selecting the Gas Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

M2 Transmitter Operator’s Manual, 12 V DC Operation

Chapter 7: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

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

Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Calibration Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Replacing Components of the M2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Chapter 8: RS-485 Modbus Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Wiring the M2 in a Modbus System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Using the M2 in a 4-wire Modbus System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Modbus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Supported Modbus Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Appendix A: Control Button Quick Reference Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Appendix B: PLC and DCS Device Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Appendix C: Function Code 16 Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

(Appendix C available from RKI Instruments, Inc. Not in manual as norm ally provided
with M2 detector head.)

M2 Transmitter Operator’s Manual, 12 VDC Operation

Chapter 1: Introduction

Overview

This chapter briefly describes the M2 Transmitter. This chapter also describes the M2
Transmitter Operator’s Manual (this document). Table 1 at the end of this chapter lists the

specifications for the M2.

About the M2 Transmitte r

The M2 Transmitter is a fixed mount, continuous-monitoring de tector head. All user
adjustable parameters may be accessed using push button switches. In addition,
calibration may be performed non-intrusively by use of a magnetic wand accessory which
activates magnetic switches through a window at the front face of the detector head.

The M2 displays the current gas reading on an LCD display wh ich is visible through the
window in the cover (front face) and provides a 4 - 20 mA signa l which indicates the
target gas reading for use by a gas monitoring controller, recording device, or
programmable controller. The M2 also provides an RS-485 Modbus output. Three sets of
relay contacts, two controlled by the gas alarms and one by the fail alarm, rated at 115
VAC 5 amps are available for controlling devices such as lights or horns or for controlling
higher rated relays.

Four operating modes allow you to display and change setup and calibration settings and
change the gas type. They are Calibration Mode, Configuration Mode, Gas Type Mode,
and Modbus Mode.

NOTE: Only the LEL version of the M2 is available for 12 VDC operation.

About this Manual

The M2 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 M2 Transmitter Operator’s Manual, 12 V DC Operation

Specifications

Table 1 lists specifications for the M2.

Table 1: M2 Specifications

Target Gas/Detection Range Combustible (LEL) Gas: 0 - 100% LEL, 1% LEL increments

Alarm Settings

*

• Alarm 1: 10 %LEL

• Alarm 2: 50 %LEL
Construction (housing) Explosion-proof Junction Box, NEMA 4
Area Classification Explosion-proof for Class I, Groups B, C, and D (LEL and toxic

versions)
Sampling Method Diffusion
Input Power 10.8 - 14.5 VDC
Controls • Three push button switches

• Three magnetic switches for non-intrusive calibration
Weight 4.5 lbs.
Signal Output • 4 to 20 mA, 350 o hms impedance max

• RS-485 Modbus
Operating Temperature -20°C to 50°C
Accuracy ± 5% of reading or ± 2% LEL (whichever is greater)

*

These are the RKI factory settings. You can change the alarm settings in Configuration Mode. See

“Viewing & Changing M2 Parameters” on page 17.

WARNING: When using the M2, you must follow the instructions and warnings in

this manual to assure proper and safe operation of the M 2 and to
minimize the risk of personal injury. Be sure to maintain and periodically
calibrate the M2 as described in this manual.

WARNING: M2 det ector heads with firmware version 5.0 or later have a different

Modbus register assignment than M2s wi th previous versions of
firmware. If you are adding M2s with firmware version 5.0 or l ater to an
existing Modbus network installation, confirm what firmware version is
installed in the M2s already in the network and if necessary, take all steps
required to address the differences in Modbus register assignments. See
“Supported Modbus Functions” on page 33 for information on the current
Modbus register assignments. The firmware version i s shown on the
Information Screen described on page 13.

M2 Transmitter Operator’s Manual, 12 VDC Operation 2

Chapter 2: Description

Overview

This chapter describes external and internal components of the M2 Transmitter.

External Description

This section describes the junction box and all external components of the M2 transmitter.

Junction Box Cover

3/4NPT Conduit Hub

Mounting Slot (2x)

Window

Detector

(Catalyti c LEL D etector Shown)

Magnetic

Wand

Figure 1: M2 External Component s

Junction Box

The M2’s cast aluminum junctio n box is dust an d weath er resistant. The junction box also
protects the M2 and all connections made to it. Use the two 3/4 in. conduit hubs to mount
the detector to the junction box (factory installed in the bottom hub) and conn ect wirin g
from an external device (top hub).

Use the junction box’s two mounting holes to mount the M2 to a vertical surface at the
monitoring site. The window in the cover on the front of the junction box allows you to
view the LCD display and use the magnetic wand to actuate the magnetic control
switches so you can perform non-intrusive calibration. Removing the cover allows you to
access the interior of the junction box.

3 M2 Transmitter Operator’s Manual, 12 V DC Operation

Magnetic Wand

O

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.

LEL Detector

The LEL detector senses the target gas and is mounted in a 3/4” conduit hub on the right
bottom side of the M2. The L EL detector ha s a 1/2” NPT th rea d and r e quir es a 3/4”NPT x
1/2”NPT reducer to mount it in the detector hub.

Internal Description

3/4" NPT C onduit Opening

Power/Signal

Terminal Stri p

Dete ctor Termi nal Strip

(Comb/CO2 VersionShown)

Detector Current Pot

(Comb/CO2 T ype

nly, FactoryAdjust)

forWire Entry

Relay
Terminal
Strips

Junction B ox

TerminalPCB

Control P CB

Magnetic
Switches

UP/YES

Fail LED

Alarm 1 LED

Alarm 2 LED

RXLED

TX LED

DOWN/NO

PWR/SIG

FAIL

- S +

PWR/SIG

- S +

LEL

R W G B

RS 485

A B C

C NC NO

LEL

ALARM 1

C NC NO

R W G B

ALARM 2

C NC NO

RS 485

A B C

ENTER

RKI INSTRUMENTS

M2 TRANSMITTER

Programmin g

Connector

(Factory Use)

Modbus

Termin a l Strip

Push Button

Control

Display Ribbon
Cable Connector

Termination Jumper

Switches

UP/YES

DOW N/NO

ENTER

LCD Display

View With Cover and

ControlPCB Removed

View With Cover Removed

Figure 2: M2 Internal Component s

M2 Transmitter Operator’s Manual, 12 VDC Operation 4

Terminal PCB

The terminal PCB is encapsulated in epoxy for protection against moisture and physical
damage. It is mounted into the rear of the junction box with three standoffs and rests on a
thin layer of foam. A banana jack is screwed into each of the standoffs and used for
mounting the control PCB. The terminal PCB converts the electrical output from the
detector to a signal which can be displayed by the LCD display, a 4 - 20 mA signal (that is
proportional to the detection range) and an RS-485 Modbus output signa l. The 4 - 20 mA
signal may be used by a recording device, gas monitor controller, or programmable
controller. The Modbus output may be used to connect the M2 to a Modbus network. The
terminal PCB also controls three relays, one fail and two gas alarm relays.

Two columns of plug-in style terminal strips are used to make all wiring connections to
the M2. The column on the left consists of the power/signal, detector, and Modbus
terminal strips. The column on the right consists of the relay terminal strips. A 20 position
connector at the bottom of the terminal PCB is used to connect the terminal PCB to the
control PCB with a ribbon cable. A 5 position connector on the left side of the terminal
PCB is used by factory or field service personnel to program the M2. A factory adjust pot
just above the programming connector is used to set the LEL detector current.

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 12 VDC power to the M2 and to
connect the 4 - 20 mA output signal to a device.

The signal output, the S terminal, does not have to be connected for the M2 to function.
The S terminal is used if you want to connect the 4 - 20 mA output signal to another device
such as a gas monitoring controller, chart recorder, or programmable controller (PLC).

Detector Terminal Strip

The detector terminal strip is a four position plug-in style terminal strip and is the middle
terminal strip in the left terminal column. It is used to connect the LEL detector to the M2.

NOTE: The LEL detector is factory-wired to the M2. See “Wiring the M2 Transmitter”

on page 9 for all wiring procedures related to M2.

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 M2 into a
Modbus network.

Relay Terminal Strips

The right column of terminal strips consists of, from top to bottom, the fail, alarm 1, and
alarm 2 relay terminal strips. 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. The jumper has no function unless the M2 is wired into a Modbus
installation. See “Chapter 8: RS-485 Modbus Output” on page 29 for a description of using
the M2 in a Modbus system.

5 M2 Transmitter Operator’s Manual, 12 V DC Operation

Control PCB

The LCD display and control switches are located on the control PCB. It is installed on top
of the terminal PCB by lining up its three spacing standoffs with the banana jacks in the
terminal PCB mounting standoffs and pushing it ont o the banana jacks. The jacks retain
the control PCB.

LCD Display

The LCD display is located at the top of the control PCB. It indicates the current gas
reading and displays messages and parameters in the M2’s programs.

Control Buttons

The M2 includes three push button switches that allow you to enter the M2’s operating
modes, navigate through the modes, update settings, 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: M2 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.

M2 Transmitter Operator’s Manual, 12 VDC Operation 6

Status LEDs

The M2 includes five status LEDs that are located above the display (see Figure 2).

• Fail LED
The fail LED turns on when the M2 is experiencing a fa il condition. A fail condition

can be caused by a detector failure or low detector signal.

• Alarm 1 LED
The alarm 1 LED is on when the M2 is experiencing an alarm 1 condition.

• Alarm 2 LED
The alarm 2 LED is on when the M2 is experiencing an alarm 2 condition.

• RX & TX LED’s
These LED’s indicate data being received (RX) and transmitted (TX) when the M2’s

Modbus output is operating.

7 M2 Transmitter Operator’s Manual, 12 V DC Operation

Chapter 3: Installation & Startup

b

Overview

This chapter describes procedures to mount the M2 Transmitter in the monitoring
environment and wire it to input power and devices.

Mounting the M2 Transmitter

1. Select a mounting site that is representative of the monitoring environment. Consider
the following when you select the mounting site.

• Select a site where the M2 is not likely to be bumped or disturbed. Make sure

there is sufficient room to perform start-up, maintenance, and calibration
procedures.

• Select a site where the target gas is likely to be found first. For lighter gases,

mount the detector near the ceiling; for heavier gases, mount the detector near the
floor.

5.86

2. At the monitoring site, use #10 screws through the junction box’s two mounting holes
to secure the junction box to a vertical surface. Figure 3 shows the outline and
mounting dimensions of the M2. Mount the M2 w ith the detector facing down as
shown in Figure 3.

4.59

2.41

5.23

5.00

3/4 NPT
Conduit Hu

7.7 max

1 1/2-2 0 For
Calibration Cup

1.02

Figure 3: Outline & Mounting Dimensions, LEL

M2 Transmitter Operator’s Manual, 12 VDC Operation 8

.4 7 (2X)

.3 0 (2X)

2.3 max

Wiring the M2 Transmitter

WARNING: Always verify that the power source is OFF before making any wiring

connections.

1. Remove the junction box cover.

2. Grasp the control PCB by its edges.

3. Gently pull until the control PCB is pulled away from the banana jacks. Take care not
to pull too hard and damage the cable which connects the cont rol and terminal PCB’s.

4. Let the control PCB hang by the cable. The terminal strips are now visible on the
terminal PCB. The control PCB may be left hanging while wiring is done. If desired,
the control PCB may be disconnected from the cable and set aside while wiring.

5. The detector leads are factory wired. Verify that the detector leads are wired to the
detector terminal strip as shown below: Red wire to terminal labeled LEL R, white
wire to terminal labeled LEL W, green wire to terminal labeled LEL G, black wire to
terminal labeled LEL B.

Black

Green

White

Red

S

PWR/SIG

S

PWR/SIGLEL

LEL

R W G B

R W G B

RS 485

A B C

RS 485

A B C

ALARM 2 ALARM 1 FAIL

C NC NO C NC NO C NC NO

Figure 4: LEL Detector Wiring

6. To gain access to a plug-in terminal strip for wiring, pull it out of its socket by
grasping the wall between two terminal positions with needle nose pliers and pulling.
Be careful not to exert too much force on the wall to avoid damage to the terminal
strip. The detector terminal strip and th e alarm 1 r elay t ermi nal strip ma y be r emo ved
by grasping them with you fingers if the adjacent terminal strips have been removed.

7. 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 the M2 is wired to a gas monitoring controller or just to power, whether any
relays are used, and whether the Modbus output is used.

NOTE: If the M2 is being wired to a PLC or DCS device, see “Appendix B: PLC and

DCS Device Wiring” on page 40, then continue with step 8.

Use the following recommendations to determine how to wire the M2:

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

9 M2 Transmitter Operator’s Manual, 12 V DC Operation

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.

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 M2 in conduit. Use shielded cable in the conduit for the PWR/
SIG connections and unshielded cable or individual wires for the relay
connections. Make sure any wire or cable used for relay wiring is appropriately
rated for the power that it will carry.

NOTE: If shielded cable is used for the PWR/SIG connections, leave the cable shield’s

drain wire insulated and disconnected at the M2. You will connect the opposite
end of the cable’s drain wire at the controller or device.

• If the M2 will be wired into a Modbus network, see “Chapter 8: RS-485 Modbus

Output” on page 29.

See Figure 5 below for field wiring connections to the M2.

CAUTION: Do not connect 24 VDC power to a 12 VDC M2.

WARNING: If the M 2 is installed in a hazardous location, use appropriatel y rated

conduit, conduit fittings, and constr uction technique.

RKI Controller

Terminals

(24 VDC) +

4 -20 mA In (S)

(24VDC) -

Alarm Device

Power

FAIL

C NC NO

See

S

PWR/SIG

+

Detector

Wiring

TOXIC OXY

+

C NC NO

ALARM 1

See

Modbus

Wiring

A B C

RS 485

C NC NO

ALARM 2

Typical Alarm
WiringShown

Figure 5: Wiring the M2 to a Controller and Alarm Devices

Fail Alarm
Device

Alarm 1
Alarm Device

Alarm 2
Alarm Device

M2 Transmitter Operator’s Manual, 12 VDC Operation 10

Start Up

8. 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.

9. Secure the junction box cover to the junction box.

10. Make controller, device, an d 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.

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
M2.

5. The LCD display will indicate the firmware version when the M2 is first powered up
and will then count down a o ne minute warm-up period b efore normal ope ration
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

CAUTION: Allow the M2’s detector to warm up for 15 minutes before you continue with the

next section, “Adj usting the Fresh Air Reading.”

Adjusting the Fresh Air Reading

When the M2 is shipped from RKI Instruments, Inc. it is factory calibrated. If a full
calibration is desired at startup, see “Calibration” on page 25.

Verify that the M2 is in a fresh air environment (environment known to be free of the
target gas and combustible or toxic gas vapors and of normal oxygen content, 20.9%).

CAUTION: If you suspect the presence of combustible gas, toxic gas, or that the oxygen content

is not normal in the monitoring environment, u se the calibration kit an d the zero
air calibration cylinder to introduce “fresh air” to the detector and verify an
accurate fresh air setting. See “Calibration” on page 25 for instructions on how to
use a zero air cylinder when performing a fresh air adjustment.

Non-Intrusive Fresh Air Signal Adjustment

If the M2 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

11 M2 Transmitter Operator’s Manual, 12 V DC Operation

control switch button, touch the magnet in the end of the magnetic wand to the M2’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.

WARNING: The M2 is not an active gas monitoring devi ce 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 M2 is in Calibration
Mode. The output signal will not indicate current readings and the relays
will not resume operating normally until the M2 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 M2 Parameters” on page 17 for instructions to change
the calibration time-out.

Adjusting the Fresh Air Reading

1. While in normal operation, press and hold the UP/YES button for 5 seconds to enter
Calibration Mode. Release the button when the following screen appears.

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 M2 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 M2 will return to normal operation.

M2 Transmitter Operator’s Manual, 12 VDC Operation 12

Chapter 4: Operation

Overview

This chapter describes the M2 in normal operation. This chapter also describes the M2 in
alarm 1, alarm 2, and fail conditions and sugges t s response to these conditions.

Normal Operation

Normal operation is defined as follows:

• The start-up procedure is complete.

• The M2 is not indicating an alarm 1, alarm 2, or fail condition.

• The M2 is not in Calibration, Configuration, or Gas Type modes.

During normal operation, the M2 simultaneously displays the current gas reading, unit of
measure, and target gas. The example below illustrates a typical LEL M2.

METHANE

0 %LEL

Information Screen

The Information Screen displays the M2’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.

12.1V
v5.0L 1B

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 M2. The
second line indicates the firmware that is running, version 5.0 in this example, and the
M2’s hardware version, version 1B in this example. This information may be useful if
you need to contact the factory with question s about the M2.

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.

4 - 20 mA Signal Output Operation

The output at the S terminal of the power/signal terminal strip is a 4 - 20 mA signal that is
proportional to the detection range of the detector head. Du ring normal operation, this
signal tracks the gas concentration on the LCD.

There are several cir cumstances where th e signal output will not track the display reading
but will behave as follows:

13 M2 Transmitter Operator’s Manual, 12 V DC Operation

• When the M2 is in its warm-up period, the signal output will be fixed at 3.5 mA (zero).

• When the M2’s gas type is changed, the M2 will enter Configuration Mode for you to
verify the parameter settings. When you exit Configuration Mode, the dis play will
indicate NEEDS CALIBRATION and will continue to indicate this until Calibration
Mode is entered and a calibration is performed. In this situation, the signal output will
be fixed at 3.5 mA from the time Gas Type Mode is entered until the M2 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 M2 returns to normal
operation.

• If the M2’s input power decreases below 10.5 volts so that the M2 is in a low power
alarm, the signal output is fixed below 2.4 mA until the low power alarm is cleared.

• If the M2 goes into a fail condition, after a 30 second d e lay, 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 downscal e 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 M2 includes al arm o n an d a la rm off delay settings for alarm 1 and alarm 2.

The alarm indications described in this section operate according to the factory
set alarm settings. See Table 5 on page 18 for all the factory settings.

Table 4: Visual and Audible Alarm Indications

Condition Cause Visual Indication(s)

Alarm 1

1

Increasing gas reading at or above the
alarm 1 setpoint

• A1 LED is on

• Gas reading alternates

with ALARM-1 message

Alarm 2

1

Increasing gas reading at or above the
alarm 2 setpoint

• 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

• F LED is on

• FAIL message replaces

gas reading

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

Low Power DC power source less than 10.5 volts. • F LED is on

• LowPower message and

actual voltage of
incoming DC power

*1If the M2 is in both an ala r m 1 and an a l arm 2 c ondition, both alarm LEDs are on an d t he

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

M2 Transmitter Operator’s Manual, 12 VDC Operation 14

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. DE-EN and is not user-adjustabl e.

Alarm 1 Condition

Alarm 1 Condition Indications

When the gas reading reaches the alarm 1 setpoint, the M2 senses an alarm 1 condition.
The M2 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 circuit. Resetting the alarm 1 circuit turns off the A1 LED, resets the LCD,
and de-energizes the alarm 1 relay.

NOTE: If the ENTER button is pressed while the M2 is in an alarm 1 cond ition, the A1

LED will flash but all other indica tions 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 reading reaches the alarm 2 setpoint, the M2 senses an alarm 2 condition.
The M2 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.

NOTE: If the M2 is in both an alar m 1 and al arm 2 cond ition , both the A1 and A2 LED s

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 LCD, and
de-energizes the alarm 2 relay.

15 M2 Transmitter Operator’s Manual, 12 V DC Operation

NOTE: If the ENTER button is pressed while the M2 is in an alarm 2 cond ition, the A2

LED will flash but all other indica tions 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 M2 indicates a fail condition for any of the following:

• The detector wiring is disconnected or incorrectly connected.

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

When the M2 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

Verify that the detector wiring is correctly and securely connected.

Low Power Alarm

Low Power Alarm Indications

The M2 senses a low power condition when the DC power source is 10.5 volts or less.

WARNING: While in a lo w power condition, the M2 is not an active gas monitor.

When the M2 senses a low power condi tion, it alerts you as follows:

• The F LED turns on.

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

• The fail relay de-energizes.

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

When the voltage increases to 10.7 volts, the low power alarm is cleared and the M2 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 10.7 volts, the M2 will begin its warm-up
sequence.

3. Verify that the M2 enters normal operation after its warm-up sequence. If necessary,
perform a fresh air adjustment. See “Adjusting the Fresh Air Reading” on page 11.

M2 Transmitter Operator’s Manual, 12 VDC Operation 16

Chapter 5: Configuration Mode

Overview

This chapter describes how to view and change M2 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 M2 automatically returns to no rmal operation.

NOTE: If the M2 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 M2, it has been setup at the factory. Use
Configuration Mode only if you want to change the M2’s setup. If you want to
change the detector type see “Chapter 6: Gas Type Mode” on page 20.

Viewing & Changing M2 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 M2 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 M2 parameters you can set. Table 5 also lists the factory set value for
each parameter.

17 M2 Transmitter Operator’s Manual, 12 V DC Operation

Table 5: Configuration Parameters

Parameter

(Factory Set Value)

ALARM-1 (level)
(See “M2 Specifications” on page 2)

ALARM-1 (activation)
(Increase)

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

ALARM-1 (relay reset)
(LA TCH)

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

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

Description

The gas reading at which the M2 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 N. DE-EN, the ala rm 1 relay is de-ene rgized in normal operatio n
and energizes when an alarm 1 condition is initiated.
If set as N. EN, the alarm 1 relay is energized in normal operation and
de-energizes when an alarm 1 cond ition is initiated.

If set as LATCH, you must press the ENTER button to reset the alarm 1
circuit after the alarm 1 condition passes.
If set as SELF-RST, the M2 automatically resets the alarm 1 circuit after
the alarm 1 condition passes.

The amount of time the M2 delays activation of the alarm 1 circuit once
an alarm 1 conditio n is ini tiated . It is se ttable in 1 sec ond incr ements from
0 - 60 seconds, in 1 minute increments from 1 - 15 minutes, and in 15
minute increments from 15 - 60 minutes.

The amount of time the M2 delays 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 SELF--RST. It is settable in 1 second
increments from 0 - 60 seconds, in 1 minute increments from 1 - 15
minutes, and in 15 minut e increments from 15 - 60 minutes.

ALARM-2 (level)
(See “M2 Specifications” on page 2)

ALARM-2 (activation)
(Increase)

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

ALARM-2 (relay reset)
(LA TCH)

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

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

The gas reading at which the M2 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 N. DE-EN, the ala rm 2 relay is de-ene rgized in normal operatio n
and energizes when an alarm 2 condition is initiated.
If set as N. EN, the alarm 2 relay is energized in normal operation and
de-energizes when an alarm 2 cond ition is initiated.

If set as LATCH, you must press the ENTER button to reset the alarm 2
circuit after the alarm 2 condition passes.
If set as SELF-RST, the M2 automatically resets the alarm 2 circuit after
the alarm 2 condition passes.

The amount of time the M2 delays activation of the alarm 2 circuit once
an alarm 2 conditio n is ini tiated . It is se ttable in 1 sec ond incr ements from
0 - 60 seconds, in 1 minute increments from 1 - 15 minutes, and in 15
minute increments from 15 - 60 minutes.

The amount of time the M2 delays 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 SELF-RST. It is settable in 1 second
increments from 0 - 60 seconds, in 1 minute increments from 1 - 15
minutes, and in 15 minut e increments from 15 - 60 minutes.

M2 Transmitter Operator’s Manual, 12 VDC Operation 18

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 z ero s uppres sion sett ing fo r a com bustible detec tor is

2.0% LEL, the M2 will display a reading of 0% LEL for gas re adi ngs 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 gas reading is the average reading over the previous 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 s ets the amount of time af ter the l ast button push
while in Calibration Mo de th at the M2 will wait before returning to normal
operation. If the calibration time-out is set to 15 mins, then the M2 will
return to normal operation automatically 15 minutes after the last button
push.

If set to Enabled, the M2’s firmware will monitor the zero (fresh air)
reading and make automatic zero adjustments under precisely specified
conditions if it determine s that a reading change is due to normal sensor
drift.
If set to Disabled, the Auto Zero function is turned off.

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 M2 will return to the first
adjustable pa rameter. 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 seconds and the M2 returns to
normal operation.

19 M2 Transmitter Operator’s Manual, 12 V DC Operation

Chapter 6: Gas Type Mode

Overview

This chapter describes how to use the Gas Type Mode to select the M2’s gas type. The gas
type determines the target gas and detection range.

The Gas Type Mode includes a 5-minute time-out feature. If you do not press a button for
5 minutes, the M2 automatically returns to normal operation.

NOTE: If the M2 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.

Select
GasType?

2. If you want to exit Gas Type Mode, press and release the DOWN/NO button. The
display will indicate NO CHANGE and the M2 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 DOWN/NO button to scroll through the choices of target gas. Table 6 below
lists the choices of target gas for the M2.

Table 6: M2 Gas Types

M2 type

LEL

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

Gas Type

Choices

METHANE
HYDROGEN
HEXANE
HC

Detection Range

0 - 100% LEL for all
gas types.

M2 Transmitter Operator’s Manual, 12 VDC Operation 20

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
ABOR T? YES/ NO . Pr ess the UP/YES button. The M2 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 M2 will enter Configuration Mode automat ical ly 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 17 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, the display will ask SAVE IT? YES/NO.

8. To save the configuration settings, press and release the UP/YES button. The display
will indicate Config Saved and the M2 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 M2 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 M2 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 25 for calibration instructions.

NOTE: When calibrating an M2 after changing the gas typ e, the M2 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 calibratio n is required, the
calibration sequence will proceed without asking if you want to perform
certain operat ions.

21 M2 Transmitter Operator’s Manual, 12 V DC Operation

Chapter 7: Maintenance

Overview

This chapter describes procedures for performing preventive maintenance,
troubleshooting, calibrating the M2, and replacing field replaceable parts.

Preventive Maintenance

This section describes a recommended preventive maintenance schedule to ensure the
optimum performance of the M2. It includes daily, monthly, and quarterly procedures.

Daily

Verify a display reading of zero. Investigate significa nt cha nges in the reading.

Monthly

This procedure describes a test to verify that the M2 responds properly to the target gas.

NOTE: Performing a response test on the M2 may cause alarms. If you do not want

external alarms to act u ate, disable any external alarms duri ng t he r esponse 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, a fixed flow regulator with an on/off knob, a
calibration cup for the detector, and a short piece of sample tubing to connect
the regulator to the calibration cup.

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

2. Connect the calibration kit sample tubing to the calibration cup hose barb.

3. Screw the calibration cup onto the detector.

4. Connect the fixed flow regulator to the calibration cup using the sample tubi ng.

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

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

7. Allow calibration gas to flow for one minute.

8. 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 M2 as

described in “Calibration” on page 25.

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

10. Unscrew the calibration gas cylinder from the fixed flow regulator and unscrew the
calibration cup from the detector.

M2 Transmitter Operator’s Manual, 12 VDC Operation 22

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

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

Quarterly

Calibrate the M2 as described in “Calibration” on page 25. See “Calibration Frequency”
on page 25 for a discussion of calibration frequency guidelines.

Troubleshooting

The troubleshooting guide describes symptoms, probable causes, and recommended
action for problems you may encounter with the M2.

NOTE: This troubleshooting guide describes M2 problems only . If the M2 is connected to

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

Table 7:Troubleshooting the Combustible Gas 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 M2 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 M2 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 PCB.

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

1. Verify that the M2 wiring is
properly shielded. See “Wiring
the M2 Transmitter” on page 9.

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.

23 M2 Transmitter Operator’s Manual, 12 V DC Operation

Table 7:Troubleshooting the Combustible Gas Detector (Continued)

Condition Symptom(s) Probable Causes Recommended Action

Flickering
Display

Fail
Condition

The display reading
flickers often.

• M2 indicates a fail
condition.

• Controller
indicates a fail
condition

•The M2 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
M2 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 M2 wiring is
properly shielded. See “Wiring
the M2 Transmitter” on page 9.

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. V erify that the wiring between the
M2 and the controller is correct
and secure.

3. Calibrate the M2.

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

•M2 responds
slowly or does not
respond to
response test.

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

•M2 requires
frequent
calibration.

Note: Under “normal”
circumstances, the
detector requires
calibration once every
three months.
See “Calibration
Frequency” o n page 25 for
calibration frequenc y
guidelines.

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

•The detector is
malfunctioning.

• The terminal PCB is
malfunctioning.

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

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

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

M2 Transmitter Operator’s Manual, 12 VDC Operation 24

Calibration Frequency

Although there is no particular calibration frequency that is correct for all applications, a
calibration frequency of every 3 to 6 months is adequate for most M2 applications. Unless
experience in a particular application dictates otherwise, RKI Instruments, Inc.
recommends a calibration frequency of every 3 months.

If an application is not very demanding, for example detection in a clean, temperature
controlled environment where the toxic or co mbustible tar get gas is not normally pr esen t,
and calibrati on adjustments are mi nimal at calibration, then a cali bration frequenc y of
every 6 months is adequate.

If an application is very demanding, for example if a combustible or toxic gas is present
often and in significant concentrations or the environment is not well controlled, then
more frequent calibration than every 3 months may be necessary. For combustible gas
detection, if potential catalyst poisons are known or likely to be present, more frequent
calibration than every 3 months will be necessary.

Calibration

This section describes how to calibrate the M2. 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 M2 is not an active gas monitoring devi ce 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 M2 is in Calibration
Mode. The output signal will not indicate current readings and the relays
will not resume operating normally until the M2 is in normal operation
again.

Prepari ng for Ca libration

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

calibration gas cylinder, a zero air cylinder, a fixed flow regulator with a n on/
off knob, a calibration cup for the appropriate sensor, and a short piece of
sample tubing to connect the regulator to the calibration cup.

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 M2 Parameters” on page 17 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.

1. Connect the calibration kit sample tubing to the calibration cup hose barb.

25 M2 Transmitter Operator’s Manual, 12 V DC Operation

2. Screw the calibration cup onto the detector.

3. Connect the fixed flow regulator to the calibration cup using the sample tubi ng.

Non-Intrusive Calibration

If the M2 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 M2’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 M2 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 M2. When zero air is applied to the M2 during a fresh air
adjustment, the M2 will freeze the display reading at the lowest response and the M2 will
continue to display this reading and retain it in its mem ory until the fresh air adjustment
procedure is completed. When calibration gas is applied to the M2 during a span
adjustment, the M2 will freeze the display reading at the highest response to the
calibration gas. The calibration gas can then be removed and the M2 will continue to
display this reading and retain it in its memory until the spa n a d justment procedure is
completed.

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 butto n. The
M2 will indicate Leaving CAL Mode and then 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. Turn the regulator knob counterclockwise to open the regulator.

6. Allow zero air to flow for two minutes. If there was gas present causing a reading on
the M2, the reading should decrease and stabilize after two minutes.

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

M2 Transmitter Operator’s Manual, 12 VDC Operation 26

8. Unscrew the zero air cylinder from the fixed flow regulator leaving the calibration cup
on the detector. The M2 will continue to display the minimum gas response on the
display and retain the response level in its memory.

9. Press and release the ENTER button. The M2 will perform a fresh air adjustment and
the display will indicate SPAN w/Cal Gas?.

NOTE: If the fresh air adjustment fai ls, see “Troubleshoot i ng” on pag e 23 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 M2 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 two minutes. The gas reading should be stable af ter
two minutes.

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

6. Unscrew the calibration gas cylinder from the fixed flow regulator and unscrew the
calibration cup from the detector. The M2 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 M2 will perform a span operation. The display will indicate SPAN Gas PASS for
a few second s, then in dicat e SPAN Gas SAVED before indicating Leaving CAL Mode
for a few seconds.

NOTE: If the span adjustment fails, see “Troubleshooting” on page 23 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 M2 will return to normal
operation.

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

27 M2 Transmitter Operator’s Manual, 12 V DC Operation

Replacing Components of the M2

Replacing LEL Detector

1. Turn off or disconnect power to the M2.

2. Remove the junction box cover.

3. Grasp the control PCB by its edges.

4. 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 cont rol and terminal PCB’s.

5. 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.

6. Remove the detector terminal strip from its socket.

7. Disconnect the detector leads from the detector terminal strip. Note the position of the
color-coded leads as you remove them.

8. Unscrew the detector from the junction box.

9. Guide the replacement detector leads through the bottom conduit hub of the junction
box, then screw the mounting threads of the detector into the conduit hub.

10. Connect the detector leads to the detector terminal strip as follows:
Red wire to terminal labeled LEL RED, white to terminal labeled LEL WHT, green

wire to terminal labeled LEL GRN, black wire to terminal labeled LEL BLK.

11. Re-install the detector terminal strip into its socket.

12. Re-install the control PCB (and ribbon cable if necessary). Be sure the ribbon cable is
routed down below the control PCB so it will not be damaged by the cover when it is
screwed back on.

13. Secure the junction box cover to the junction box.

14. Turn on or reconnect power to the M2.

CAUTION: Allow the replacement detecto r to warm up for 15 minutes before you continue

with the next step.

15. Calibrate the replacement detector as described in “Calibration” on page 25.

M2 Transmitter Operator’s Manual, 12 VDC Operation 28

Chapter 8: RS-485 Modbus Output

Overview

This chapter describes the M2’s RS-485 Modbus output and how to configure the M2 to
make use of it. It also discusses how to wire the M2 into a Modbus syst e m.

The M2 provides an RS-485 serial communications interface. It is a Modbus Slave Device,
supporting 2-wire RS-485 Modbus RTU serial communicatio ns.

Wiring the M2 in a Modbus System

When wiring the M2 into a Modbus system, adhere to standard Modbus wiring practices
per the Modbus Over Serial Line Specification and Implementation Guide V1.0 or later.
This document can be found online at www.modbus.org/specs.php.

The Modbus protocol supports a maximum of 247 unique slave addresses (1-247). The
M2’s line driver provides for up to 128 M2s to be connected together without the need for
a repeater. Figure 6 & Figure 7 below illustrate typical M2 wiring configurations. If more
than 128 M2s need to be connected together, RS-485 repeater(s) should be used such that
no more than 128 M2s reside on any given network segment.

CAUTION: The network segment can only support 128 units if RKI M2s are being used. The

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

NOTE: Only M2s produced after November 2010 have the capability to support a 128-

unit segment. M2s produced before November 2010 can only support a 32-unit
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

Termination Jumper

The M2 includes a 2-pin termination header (see Figure 2) that is used when the M2 is
used in a Modbus system. Every M2 is supplied with a termination jumper (a jumper
block) installed onto this header. If the M2 is not used in a Modbus system, this jumper
has no function. When the M2 is installed in a Modbus system, this jumper must be

29 M2 Transmitter Operator’s Manual, 12 V DC Operation

installed in an M2 that is at the end of a Modbus line. Any M2 in a Modbus system that is

ID = 128

ID = 128

7

Up to 128 M2s can be connected without a repeater.

not at the end of a line must have the termination jumper removed (see Figure 6 &
Figure 7 below).

M2

Termination

Jumper

Installed

Modbus

Master

RS-485 RS-485

Up to 128 M2s can be connected without a repeater.

M2

Termination

Jumper

Not Installed

M2

Termination

Jumper

Not Installed

M2

Termination

Jumper

Not Installed

M2

Termination

Jumper

Not Installed

ID = 127 ID = 126 ID = 125 ID = 1

Figure 6: Multiple M2s in a Daisy Chain Configuration

ID = 1

M2

Termination

Jumper

Installed

Modbus

Master

M2

Termination

Jumper

Installed

RS-485 RS-485

M2

Termination

Jumper

Not Installed

ID = 2 ID = 3 ID = 4

Figure 7: Multiple M2s in a Two Branch Configuration

M2 Transmitter Operator’s Manual, 12 VDC Operation 30

M2

Termination

Jumper

Not Installed

M2

Termination

Jumper

Not Installed

M2

Termination

Jumper

Not Installed

ID = 12

Using the M2 in a 4-wire Modbus System

The M2 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 M2s.

• Manage any pull-up, pull-down, and/or termination jumpers as appropriate for a 2­wire Modbus network.

Modbus Mode

Modbus Mode allows you to configure various parameters relating to the Modbus setup
of the M2. Modbus Mode includes a 5-minute time-out feature. If you do not press a
control button for 5 minutes, the M2 automatically returns to norma l operation.

NOTE: If the M2 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. To exit Modbus Mode, press and release the DOWN/NO button. The M2 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 M2 Modbus Mode p ara me te rs you can set. Table 9 also lists the
factory set value for each parameter.

31 M2 Transmitter Operator’s Manual, 12 V DC Operation

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 M2 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 delay inserted by the M2 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/YE S 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 M2 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 M2 returns to
normal operation.

NOTE: All M2s on a Modbus network must be configured with the same baud rate and

parity, and each M2 must have a unique slave ID. For an M2 to participate on a
network, the ENABLED/DISABLED setting must be set to ENABLE.

M2 Transmitter Operator’s Manual, 12 VDC Operation 32

Supported Modbus Functions

The M2 supports Function Code 03: Read Holding Registers and Function Code 16: Write
Registers. The register assignments detailed below were implemented in M2 firmware
version 5.0. Please see revision 0 of the 12 V M2 manual if you have an M2 with a
firmware version previous to 5.0.

WARNING: Do not attempt to use registers according to the instructions below with

units that have firmware versions previous to 5.0. For the Modbus register
assignments of M2s with firmware previous to 5.0, see revision 0 of the 12
VDC M2 Operator’s Manual. The firmware version is shown on the
Information Screen described on page 13.

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 as signments) for registers 1 - 2 is shown below in Table 10 and
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

33 M2 Transmitter Operator’s Manual, 12 V DC Operation

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

Bit(s) Value

[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
[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 M2’s LCD (not NULL terminated).

M2 Transmitter Operator’s Manual, 12 VDC Operation 34

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.

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

35 M2 Transmitter Operator’s Manual, 12 V DC Operation

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.

Register 33

Register 33 is zero suppression.
Toxics and LEL: 0%-6% of full scale
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

M2 Transmitter Operator’s Manual, 12 VDC Operation 36

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

Function Code 16: Write Registers

There are 21 registers in Function Code 16 that can be used to write to the M2. 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 M2. It is useful for
remotely silencing alarms. With the M2 in an alarm condition, bit [0] can be 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 (also used for “Alarm Reset”)

0=Not Pressed

1=Pressed

37 M2 Transmitter Operator’s Manual, 12 V DC Operation

Parts List

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

07-0203RK Rubber retaining boot for charcoal filter
18-0431RK-02 Junction box
33-7101RK C h arcoal filter disk
45-6132RK Termination jumper
61-0140RK LEL detector
71-0115RK M2 Transmitter for 12 VDC Operation Operator’s Manual (this document)

Table 13 lists replacement parts and accessories for the M2 Transmitter.

Table 13: Parts List

Part Number Description

ordering)

81-0002RK-01 Calibration cylinder, 50% LEL hydrogen; 34 liter steel
81-0007RK-01 Calibration cylin der, 15% LEL hexane; 34 liter steel
81-0012RK-01 Calibration cylin der, 50% LEL methane; 34 liter steel
81-0076RK-01 Zero air calibration cylinder, 34 liter steel
81-1050RK Regulator, with gauge and knob, 0.5 liter/minute continuous flow, for

combustible gas, nitrogen, and CO cylinders

81-1051RK Regulator, with gauge and knob, 0.5 liter/minute continuous flow, for

H2S cylinder
81-1117RK Calibration cup
NC-6234-01K Hydrogen specific LEL detector

M2 Transmitter Operator’s Manual, 12 VDC Operation 38

Appendix A: Control Button Quick Reference Guide

The M2’s control 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

• M2 Version/Revision Information

• Fresh Air Adjust

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

• Alarm Levels

• Increasing or Decreasing 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

39 M2 Transmitter Operator’s Manual, 12 V DC Operation

• Enable or Disable Modbus

•Slave ID

•Baud Rate

•Parity

• Response Delay

Appendix B: PLC and DCS Device Wiring

The M2 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 M2:

• 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 M2 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 M2. You will connect the opposite
end of the cable’s drain wire at the controller or device.

• If the M2 will be wired into a Modbus network, see “Chapter 8: RS-485 Modbus

Output” on page 29.

CAUTION: Do not connect 24 VDC power to a 12 VDC M2.

Max Distance to Controller

w/16 Gauge Wire

Max Distance to Controller

w/14 Gauge Wire

M2 Transmitter Operator’s Manual, 12 VDC Operation 40

24VDC

Power Supply

24 VDC +

See Figure 8 below for field wiring connections to the M2.

24VDC -

4 -20 mA In (S)

(24VDC) -

Controller

(PLC, DCS)

Alarm Device

FAIL

C NC NO

See

S

PWR/SIG

+

Detector

Wiring

TOXIC OXY

+

C NC NO

ALARM 1

See

Modbus

Wiring

A B C

RS 485

C NC NO

ALARM 2

Figure 8: PLC and DCS Device Wiring

Power

Fail Alarm
Device

Alarm 1
Alarm Device

Alarm 2
Alarm Device

Typical A larm
WiringShown

41 M2 Transmitter Operator’s Manual, 12 V DC Operation

Appendix C: Function Code 16 Registers

The M2 supports Function Code 16 that allows writing to the M2. There are 21 registers in
this Function Code. The register assignments detailed below were implemented in M2
firmware version 5.0. Please see revision 0 of the 12 VDC M2 manual if you have an M2
with a firmware version previous to 5.0.

WARNING: Do not attempt to use registers according to the instructions below with

units that have firmware versions previous to 5.0. For the Modbus register
assignments of M2s with firmware previous to 5.0, see revision 0 of the 12
VDC M2 Operator’s Manual. The firmware version is shown on the
Information Screen described on page 13.

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

M2 Transmitter Operator’s Manual, 12 VDC Operation 42

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
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
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 M2 manual.

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.

Register 19

Register 19 is for clearing change flags. When parameters are changed at the M2, 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

43 M2 Transmitter Operator’s Manual, 12 V DC Operation

Bit(s) Value & Field

[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

M2 Transmitter Operator’s Manual, 12 VDC Operation 44