RKI Instruments 65-2615RK-05-04 User Manual

65-2615RK-05-04

M2 Transmitter

Operator’s Manual

Part Number: 71-0326

Revision: P1

Released: 6/20/14

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

65-2615RK-05-04 M2 Transmitter Operator’s Manual

Product Warranty

RKI Instruments, Inc. warrants gas alarm equipment sold by us to be free from defects in
materials, workmanship, and performance for a period of one year 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 a n y a c c ident or damage caus e d b y t he op e ration of
this gas monitor, and our warranty is limited to the replacement of parts or our complete
goods.

65-2615RK-05-04 M2 Transmitter Op erator’s Manual

Table of Contents

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

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

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

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

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

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

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

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

Internal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Chapter 3: Installation & Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Mounting the M2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Wiring the M2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

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

Chapter 4: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Information Screen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4 - 20 mA Signal Output Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Alarm Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Chapter 5: Configuration Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Viewing & Changing M2 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Chapter 6: Gas Type Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Selecting the Gas Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

65-2615RK-05-04 M2 Transmitter Operator’s Manual

Chapter 7: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

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

Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Calibration Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Replacing Components of the H2S Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Chapter 8: RS-485 Modbus Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Wiring the M2 in a Modbus System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Using the M2 in a 4-wire Modbus System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Modbus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Supported Modbus Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Appendix A: Control Button Quick Reference Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Appendix B: PLC and DCS Device Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Appendix C: Function Code 16 Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

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

65-2615RK-05-04 M2 Transmitter Op erator’s Manual

Chapter 1: Introduction

Overview

This chapter briefly describes the 65-2615RK-05-04 M2 Transmitter. This chapter also
describes the 65-2615RK-05-04 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 detector hea d. 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.

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 65-2615RK-05-04 M2 Transmitter Operator’s Manual

Specifications

Table 1 lists specifications for the M2.

Table 1: M2 Specifications

Target Gas/Detection Range Hydrogen Sulfide:

0 - 100 ppm, 1 ppm increments
Alarm Sett ings (Alarm 1/Alarm 2) 10 ppm/50 ppm*
Construction (housing) Explosion-proof Junction Box, NEMA 4
Area Classification Explosion-proof for Class I, Groups B, C, and D
Sampling Method Diffusion
Input Power 19 - 30 VDC
Controls • Three push button switches

• Three magnetic switches for non-intrusive calibration
Weight 5.5 lbs.
Signal Output • 4 to 20 mA, 500 ohms impedance max

• RS-485 Modbus
Operating Temperature -20°C to 50°C
Accuracy ± 5% of reading or ± 2 ppm H

*

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

S (whichever is greater)

2

“Viewing & Changing M2 Parameters” on page 23.

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 42 for information on the current
Modbus register assignments. The firmware version i s shown on the
Information Screen described on page 18.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 2

Chapter 2: Description

Overview

This chapter describes the components of the M2 transmitter. The transmitter is a 4 - 20
mA type detector head. It consists of the H

terminal PCB, the M2 junction box, and the detector junction box. The two junction box
configuration is intended for situations where the detector needs to be installed at an
inaccessible location. The detector junction box can be installed at the inaccessible location
and the M2 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 M2
transmitter.

M ounting Slot ( 2x)

Magnetic
Wand

3/4" NPT Conduit Hub

S detector, calibration adapter/splash guard,

2

Term i nal
Strip

Wi ndow

3/4" NPT

Conduit

M2

Junction

Box

Figure 1: M2 External Component s

3 65-2615RK-05-04 M2 Transmitter Operator’s Manual

Junction Box

Hydrogen Sulfide

Calibration Adapter/

Splash G u ard

Hub

Detector

Detector

M2 Junction Box

r

The M2’s cast aluminum junction box protects the terminal PCB and wiring connections
made to the terminal PCB. Use the top 3/4’’ conduit hub to connect wiring from the
terminal PCB to external power and/or to an external device, typically an RKI controller.
Use the bottom 3/4” conduit hub to wire the remotely installed H

S detector. Use the

2

junction box’s two mounting slots 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.

Detector Junction Box

The detector junction box is intended to be installed remotely from the M2 junction box.
The H

S detector is factory installed in the bottom 3/4” NPT conduit hub. A terminal strip

2

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 M2 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.

H2S Detector

The H2S detector consists of the detector housing body, detector housing cap, cap gasket,
rubber boot, spacer, and the plug-in sensor.

Detector Housing Body

Cap Gasket

H2S Plug-in Sensor

Spacer

Rubber Boot

Detector Housing Cap

Flame Arresto
Guard

Figure 1: H

S Detector Component Location

2

Detector Housing Body

The detector housing body protects the electronic components within the housing. Use the
mounting threads at the top of the housing to screw the H

hub on the bottom of the detector junction box. Two wires extend from the top of the

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 4

S detector into the 3/4” NPT

2

detector housing body. Use these wires to connect the H2S detector to the terminal strip.
One of the wires is red and one of the wires is black.

The housing includes a four-socket pattern. This socket pattern accepts the sensor’s four
pins to secure the sensor within the detector housing. A pre-amplifier, located between the
sockets and two interconnect wires, conditions the sensor’s signal before the signal
reaches the controller.

Housing Cap & Cap Gasket

The housing cap screws onto the detector housing. It retains the plug-in sensor and
protects it from damage. The housing cap also includes a flame arrestor which contains
any sparks that may occur within the detector and a flame arrestor guard which protects
the flame arrestor fro m damage. Unscrew the detector cap to access the plug-in sensor for
maintenance or replacement. A cap gasket seals the interface between the housing and
cap. A flame arrestor guard is permanently bonded to the cap.

Rubber Boot and Spacer

A rubber boot and spacer are installed between the detector housing cap and the sensor.
They help ensure that the sensor remains plugged into the detector housing body.

Plug-In H

The sensor is secured within the detector assembly by the housing cap. Through a series
of chemical and electrical reactions, the sensor produces an electrical output that
corresponds to the detection range of the transmitter.

S Sensor

2

Calibration Adapter/Splash Guard

A calibration adapter/splash guard is installed on the H2S 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 ( nea r the M2 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.

5 65-2615RK-05-04 M2 Transmitter Operator’s Manual

Internal Description

y

This section describes the interna l components of the M2. The internal components of the
M2 include t he t e rminal PCB which pro v i de s f or all the wiring connections to the M2 and
the control PCB which displays the gas reading and has the control buttons.

3/4" NPT Condu i t Open i ng

Power/Signal

Terminal St rip

Detector Terminal Strip

fo r Wire Entry

PWR/SIG

- S +

TOXIC OXY

+ - + -

RS 485

A B C

Ju nction Box

Relay
Terminal
Strips

Terminal PCB

Control PCB

Magnetic
Switches

UP/YES

DOWN/NO

- S +

PWR/SIG

C NC NO

+

ALARM 1 FAIL

C NC NO

TOXIC OXY

+

ALARM 2

C NC NO

R S 485

A B C

ENTER

RKI INSTRUMENTS

M2 TRAN SM ITTER

Fail LED

Alarm 1 LE D

Alarm 2 LED

RX LED

TX LED

Programming

Connector

(Factory Use)

Modbus

Terminal St rip

Termination

Push Button

C ontro l S witch e s

UP/YES

Jumper

Ribbon Cable
Connector

View WithCover and

Control PCB Removed

Display

3/4" NP T Co nd uit
Openi ng for
Detector J- Box
Wiring

DOWN/NO

ENTER

View WithCover Removed

Figure 2: M2 Internal Component s

Terminal PCB

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

Two columns of plug-in style terminal strips are used to make all wiring connections to
the M2. The column on the left consists of the power/signal, detector, and Modbus
terminal strips. The column on the right consists of the relay terminal strips. A 20 position
connector at the bottom of the terminal PCB is used to connect the terminal PCB to the

LCD Displa

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 6

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.

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 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. The two terminals labeled “TOXIC” are used to
connect the detector to the M2.

Detector

Terminal Strip

PWR/SIG

- S +

TOXI C OXY

+ - + -

RS 485

A B C

PWR/SIG

- S +

+

TOXIC OXY

+

RS 4 85

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 M2. See “Wiring the M2 Transmitter” on

page 12 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.

7 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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 37 for a description of using
the M2 in a Modbus system.

Control PCB

The LCD display and control switches are located on the control PCB. It is installed on top
of the terminal PCB by lining up its three spacing standoffs with the banana jacks in the
terminal PCB mounting standoffs and pushing it 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 (see “Information Screen” on page 18).

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 8

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.

9 65-2615RK-05-04 M2 Transmitter Operator’s Manual

Chapter 3: Installation & Startup

5

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.

• For the M2 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.

.86

• The junction boxes should be mounted no further than 200 feet from each other.

2. Use #10 screws through the M2 junction box’s two mounting slots to secure the
junction box to a vertical surface. Figure 4 shows the outline and mounting
dimensions the M2 junction box. Figu re 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 Hub

1.02
.4 7 (2 X)

Figure 4: Outline & Mounting Dimensions, M2 Junction Box

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 10

.3 0 (2X)

r

r,

3/4 Conduit Hub

5.25

Ø3.65

2.70 .38

Rubbe
Space
3X

H2S
Detector

11.40 Max

Calibration
Adapter/
Splash
Guard

1.13

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
M2 junction box. See the “Parts List” on page 47 for available tubing.

11 65-2615RK-05-04 M2 Transmitter Operator’s Manual

Wiring the M2 Transmitter

WARNING : Always verify that the power to the M2 is off before you make wiring

connections.

1. Confirm that no power is being applied to the M2.

2. Remove the detector junction box’s cover from the junction box.

3. Remove the M2 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 two-conductor, shielded cable or two wires in conduit through the top
conduit hub of the detector junction box. To make wiring more convenient, use wire
colors that correspond to the detector wire colors: red and black.

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 two-conductor, shielded cable or two wires in conduit
through the bottom conduit hub of the M2 junction box.

11. 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 your fingers if the adjacent terminal strips have been removed.

WARNING: If the M 2 is installed in a hazardous location, use app ropriatel y 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.

12. Pull out the detector terminal strip and connect the two wires to the terminal strip a s
follows (see Figure 6).

• Connect the wire corresponding to the detector ’s red wire to the TOXIC “+”

terminal.

• Connect the wire corresponding to the detector’s black wire to the TOXIC “-”

terminal.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 12

Detector

Terminal

Strip

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 M2 junction box’s chassis (earth) ground.

Cable

Shield

FAIL

- S +

PWR/SIG

- S +

TO XIC O X Y

+ - + -

R S 485

A B C

C NC NO

+

C NC NO

+

TOXIC OXY

ALARM 2 ALARM 1

C NC NO

R S 485 PWR/SIG

A B C

Black
Red

M2
J-Box

Black
Red

Detector J-Box

H2S Detector

Calibration Adapter/Splash Guard

Figure 6: Wiring the Detector to the M2

13. Reinstall the detector terminal strip into its socket.

14. If shielded cable is used between the detector junction box and the M2 junction box,
connect the cable’s drain wire to an available chassis (earth) ground at the M2 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 top
conduit hub of the M2 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.

13 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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

DCS Device Wiring” on page 49, 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

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 M2 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 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.

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

wire insulated and disconnected at the M2 junction box. 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 37.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 14

See Figure 7 below for field wiring connections to the M2.

RKI Controller

Terminals

(24 VDC) +

4 -20 mAIn (S)

(24VDC) -

Alarm Device

CableShield

See

Detector

Wiring

See

Modbus

Wiring

S

PWR/SIG

+

TOXIC OXY

+

A B C

RS 485

C NC NO

C NC NO

C NC NO

FAIL

ALARM 1

ALARM 2

Power

Fail
Alarm
Device

Alarm 1
Alarm
Device

Alarm 2
Alarm
Device

Typical Alarm
WiringShown

Figure 7: Wiring the M2 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.

Start Up

17. Secure the M2 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.

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 incomi ng power.

4. If necessar y, tu r n on th e cont roller or other 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.

H2S

0 ppm

15 65-2615RK-05-04 M2 Transmitter Operator’s Manual

NOTE: Allow the M2’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 M2 is shipped from RKI Instruments, Inc., it is factory calibrated. If a full
calibration is desired at startup, see “Calibration” on page 33.

Verify that the M2 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 hydrogen sulfide in the monitoring environment, use

the calibration kit and the zero air calibration cylinder to introduce “fresh air” to
the detector and verify an accurate fresh air setting. See the “Calibration” on
page 33 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 control switch button, touch the magnet in the end of the magnetic wa nd to the M2’s
glass cover directly over the magnetic switch you wish to actuate. Touching the glass and
removing the wand is the same as pressing and releasing a button. Touching the glass and
keeping the wand in place is the same as pressing and holding a button.

WARNING : The M2 i s not an active gas monitoring device dur in g 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 M2 is in
Calibration Mode. The output signal will not indicate current readings
and the relays will not resume operating normally until the M 2 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 23 for instructions to change
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.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 16

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.

17 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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 co nditions and suggests responses 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.

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.

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 2A 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.

H2S

0 ppm

24.2V
v5.0L 2A

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 18

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 M2. During 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:

• 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 con tinue 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 18.5 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 an d alarm 2.

Condition Cause Visual Indication(s)

Alarm 1

Alarm 2

1

1

The alarm indications described in this section operate according to the factory
set alarm settings. See Table 5 on page 24 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

19 65-2615RK-05-04 M2 Transmitter Operator’s Manual

• 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 18.5 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.

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 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 toxic gas con d ition.

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.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 20

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 toxic gas co nd ition.

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.

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

1. 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 18.5 volts or less.

WARNING: While in a low 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.

21 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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

When the voltage increases to 19.0 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 19.0 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 16.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 22

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 26.

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.

23 65-2615RK-05-04 M2 Transmitter Operator’s Manual

Table 5: Configuration Parameters

Parameter

(Factory Set Value)

ALARM-1 (level)
(10 ppm)

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 readin g 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
and energizes wh en 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 delays activation of the alarm 1 circuit once
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 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
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 M2 automatically resets the alarm 1 circuit after

SELF-RST. It can be set in 1 second

ALARM-2 (level)
(50 ppm)

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 readin g 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
and energizes wh en 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 delays activation of the alarm 2 circuit once
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 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
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 M2 automatically resets the alarm 2 circuit after

SELF-RST. It can be set in 1 second

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 24

Table 5: Configuration Parameters (Continued)

ZeroSupp
(2 ppm)

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 ppm for gas readings from -2 ppm to 2 ppm. 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 set s the am ount of time after th e last bu tton push
while in Calibratio n Mo de th at th e M2 will wait be fore return ing to no rma l
operation. If the calibra tion tim e-out is set to
to normal 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 M2’s firmware will monitor the zero (fresh air)

Disabled, the Auto Zero function is turned off.

2.0 ppm, the M2 will display a

15 mins, then M2 will return

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.

25 65-2615RK-05-04 M2 Transmitter Operator’s Manual

Chapter 6: Gas Type Mode

Overview

This chapter describes how to use Gas T y pe Mode to select the M2’s gas type. The gas type
determines the target gas and detection range.

CAUTION: The target gas is factory set and does not normally need to be changed. The

standard setting for the 65-2615RK-05-04 is hydrogen sulfide.

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.

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 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 M2.

H2S 0 - 100 ppm
CO 0 - 300 ppm

Table 6: Gas Types

Gas Type

Choices

Select
GasType?

Detection Range

OXYGEN 0 - 25.0% volume
SIH4 0 - 15.0 ppm
PH3 0 - 1.00 ppm
O3 0 - 1.00 ppm

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 26

Table 6: Gas Types

Gas Type

Choices

Detection Range

NO 0 - 100 ppm
HF 0 - 9.00 ppm
HCN 0 - 15.0 ppm
HCL 0 - 15.0 ppm
H2SE 0 - 5.00 ppm
GEH4 0 - 1.50 ppm
F2 0 - 3.00 ppm
CLO2 0 - 1.00 ppm
B2H6 0 - 5.00 ppm
ASH3 0 - 1.50 ppm
SO2 0 - 6.00 ppm
NH3 0 - 200 ppm
NH3 0 - 75.0 ppm
CL2 0 - 3.00 ppm
CL2 0 - 10.0 ppm

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
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 23 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 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

27 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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 33 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.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 28

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 0 ppm. In vestigate significant changes 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 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 32.

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 M2 as

described in “Calibration” on page 33.

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.

29 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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.

Quarterly

Calibrate the M2 as described in “Calibration” on page 33. See “Calibration Frequency”
on page 32 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 M2.

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

a controller, see the controller operator’s man ua l f or problems you may
encounter with the controller.

Table 7:Troubleshooting the Hydrogen Sulfide 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 PC B.

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 12.

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.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 30

Table 7:Troubleshooting the Hydrogen Sulfide 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 12.

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
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: See “Calibration
Frequency” o n page 32 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.

31 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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 hydrogen sulfide
transmitter 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 hydrogen sulfide is not normally present and calibration
adjustments are minimal at calibration, then a calibration frequency of every 6 months is
adequate.

If an application is very demanding, for example if hyd rogen sulf id e 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.

Determining Response Time

Since the detector junction box is installed remotely from the M2, the response time of the
detector will depend on the length of flexible tubing tha t is attached to the calibration
adapter/splash guard. To determine the response time based on the length of tubing
connected:

1. Place the M2 into its calibration mode or disable external alarms.

2. Note the current gas reading displayed at the M2.

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 .

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 32

Calibration

This section describes how to calibrate the M2 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 M2 i s not an active gas monitoring device dur ing 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: 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 M2 Parameters” on page 23 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 reading.

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 th e same operat ion as pres sing a contr ol s witch
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.

33 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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
M2 will indicate Leaving CAL Mode and the M2 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 32.

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 M2 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 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 ing ” on page 30 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 the length of time determined in “D et ermining

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 34

Response Time” on page 32.

5. Turn the regulator knob clockwise to close it.

6. Unscrew the calibration gas cylinder from the fixed flow regulator. 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 30 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. 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 Components of the H2S Detector

This section includes a procedure to replace the H2S plug-in sensor and the entire detector
assembly. In most case s, it is not necessary to replace the entire detector a sse mbly.

Replacing the Plug-In H

CAUTION: The sensor contai ns el ectr o lyt e whic h is a dil ute ac id. Do not disass em ble the se nso r

when replacing it with a new one. If sensor electrolyte comes in contact with your
skin, wash affected area thoroughly with soap and water.

1. Turn off or unplug power to the M2.

2. Unscrew the calibration adapter/splash gua rd from the detector hou sing cap.

3. Unscrew the detector housing cap from the detector housing body. Make sure not to
lose the cap gasket.

4. Unplug an d remove the H

5. Remove the rubber boot and spacer from the old sensor.

S Sensor

2

S sensor with the rubber boot and spacer attached.

2

35 65-2615RK-05-04 M2 Transmitter Operator’s Manual

6. Install the spacer and rubber boot onto the replacement sensor’s face.

7. Carefully plug the replacement sensor into the four-socket pattern that is located in
the detector housing.

8. Make sure the cap gasket is in place and screw the detector housing cap back onto the
detector housing body.

9. Screw the calibration adapter/splash guard back onto the detector housing cap.

10. Turn on or plug in power to the M2.

CAUTION: Allow the r ep la cem ent sens or to w arm up for 5 m inu tes before you continue with the

next step.

11. Calibrate the transmitter as described in the “Calibration” on page 33.

Replacing the H

S Detector

2

NOTE: In most cases, it is only necessary to replace the plug-in H2S sensor.

1. Turn off or unplug power to the M2.

2. Remove the detector junction box cover.

3. Unscrew the calibration adapter/splash gua rd from the detector hou sing cap.

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 13).

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

9. Reinstall t he detector junct ion box cover.

10. Turn on or plug in power to the M2.

CAUTION: Allow the replacement detector to warm up for 5 minutes before y o u c o ntinue with

the next step.

11. Calibrate the replacement detector as described in “Calibration” on page 33.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 36

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

The M2 is a 2-wire Modbus RTU device. When wiring the M2 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 ent c an 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
M2’s line driver provides for up to 128 M2s to be connected together without the need for
a repeater . Figure 10 & Figure 1 1 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

Recommended Modbus Wiring

The recommended Modbus wiring for the M2 is illustrated in Figure 8 below. In this
configuration, 5 wires are used for wiring the M2 into a Modbus system. Figure 8 also
illustrates typical alarm device wiring.

37 65-2615RK-05-04 M2 Transmitter Operator’s Manual

Power Supply

al

al

24 VDC

Input

Terminals

Modbus

Controller

Common

S

PWR/SIG

See

Detector

Wiring

D

1

D

0

TOXIC OXY

RS 485

A B C

ALARM 2 ALARM 1 FAIL

C NC NO C NC NO C NC NO

See

Detector

Wiring

S

PWR/SIG

TOXIC OXY

RS 485

A B C

ALARM 2 ALARM 1 FAIL

C NC NO C NC NO C NC NO

Figure 8: Recommended Modbus Wiring

Alternate Modbus Wiring For Existing Installations

Although the wiring shown in Figure 8 is recommended, it is possible to wire the M2 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 M2 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.

To
Addition
M2s

Power Supply

24 VDC

Common

Input

Terminals

Modbus

Controller

S

PWR/SIG

See

Detector

Wiring

D

1

D

0

TOXIC OXY

RS 485

A B C

ALARM 2 ALARM 1 FAIL

C NC NO C NC NO C NC NO

See

Detector

Wiring

S

PWR/SIG

TOXIC OXY

RS 485

A B C

ALARM 2 ALARM 1 FAIL

C NC NO C NC NO C NC NO

To
Addition
M2s

Figure 9: Alternate Modbus Wirin g

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 38

Termination Jumper

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

ID = 128

7

Up to 128 M2s can be connected without a repeater.

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

ID = 128

M2

Termination

Jumper

Installed

RS-485 RS-485

Up to 128 M2s can be connected without a repeater.

Modbus

Master

M2

Termination

Jumper

Not Installed

M2

Termination

Jumper

Not Installed

M2

Termination

Jumper

Not Installed

Figure 10: Multiple M2s in a Daisy Chain Configuration

ID = 1

M2

Termination

Jumper

Installed

RS-485 RS-485

M2

Termination

Jumper

Not Installed

M2

Termination

Jumper

Not Installed

Modbus

Master

M2

Termination

Jumper

Not Installed

M2

Termination

Jumper

Not Installed

M2

Termination

Jumper

Installed

M2

Termination

Jumper

Not Installed

ID = 2 ID = 3 ID = 4

Figure 11: Multiple M2s in a Two Branch Configuration

39 65-2615RK-05-04 M2 Transmitter Operator’s Manual

ID = 12

Using the M2 in a 4-wire Modbus System

Although 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.

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.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 40

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/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 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.

41 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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 B of the 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 B of the
M2 Operator’s Manual. The firmware version is shown on the
Information Screen described on page 18.

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

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 42

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).

43 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 44

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
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

45 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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

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 (used for “Alarm Reset”)

0=Not Pressed
1=Pressed

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 46

Parts List

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

07-0033RK Detector housing cap gasket
07-0203RK R ubber re taining boot
14-2101RK Spacer between sensor and rubber boot
18-0400RK-01 Detector junction box, with spacers
18-0431RK-02 M2 junction box
45-6132RK Termination jumper

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

Table 13: Parts List

Part Number Description

when ordering)

65-2423RK-05 H

S replacement detector assembly (in c ludes sensor), CSA classified

2

71-0326 65-2615RK-05-04 M2 Transmitter Operator’s Manual (this document)
81-0076RK-01 Zero air calibration cylinder, 34 liter steel
81-0076RK-03 Zero air calibration cylinder, 103 liter steel
81-0151RK-02 Calibration cylinder, H

81-0151RK-04 Calibration cylinder, H

S, 25 ppm in nitrogen, 58 liter aluminum

2

S, 25 ppm in nitrogen, 34 liter aluminum

2

81-1050RK Regulator, with gauge and knob, 0.5 liter/minute continuous flow
81-1116RK Calibration adapter/splash guard
ES-1537-H2S Replacement plug-in sensor, H

S

2

47 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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 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

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 48

• 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 37.

Max Distance to Controller

w/16 Gauge Wire

Max Distance to Controller

w/14 Gauge Wire

49 65-2615RK-05-04 M2 Transmitter Operator’s Manual

24 VDC

Power Suppl y

24 VDC +

See Figure 12 below for field wiring connections to the M2.

24 VDC -

4 - 20 mA In (S )

(24 VDC) -

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 12: PLC and DCS Device Wiring

Power

Fai l Alarm
Device

Ala rm 1
Ala rm Dev i ce

Ala rm 2
Ala rm Dev i ce

Typic a l Alarm
W iring Shown

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 50

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 B of the 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 B of the
M2 Operator’s Manual. The firmware version is shown on the
Information Screen described on page 18.

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

51 65-2615RK-05-04 M2 Transmitter Operator’s Manual

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
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 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.

65-2615RK-05-04 M2 Tran smitter Operator’s Manual 52

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
[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

53 65-2615RK-05-04 M2 Transmitter Operator’s Manual