RKI Instruments M2A 65-2643RK-05-04 User manual

RKI Instruments, Inc.
www.rkiinstruments.com
65-2643RK-05-04
M2A Transmitter
Operator’s Manual
Part Number: 71-0387
Revision: E
Released: 9/9/20

65-2643RK-05-04 M2A Transmitter Operator’s Manual
WARNING
Read and understand this instruction manual before operating
instrument. Improper use of the gas monitor could result in bodily
harm or death.
Periodic calibration and maintenance of the gas monitor is essential
for proper operation and correct readings. Please calibrate and
maintain this instrument regularly! Frequency of calibration depends
upon the type of use you have and the sensor types. Typical
calibration frequencies for most applications are between 3 and 6
months, but can be required more often or less often based on your
usage.

65-2643RK-05-04 M2A Transmitter Operator’s Manual
Product Warranty
RKI Instruments, Inc. warrants gas alarm equipment sold by us to be free from defects in materials,
workmanship, and performance for a period of one year from date of shipment from RKI Instruments, Inc. Any
parts found defective within that period will be repaired or replaced, at our option, free of charge. This warranty
does not apply to those items which by their nature are subject to deterioration or consumption in normal service,
and which must be cleaned, repaired, or replaced on a routine basis. Examples of such items are:
Warranty is voided by abuse including mechanical damage, alteration, rough handling, or repair procedures not
in accordance with the operator’s manual. This warranty indicates the full extent of our liability, and we are not
responsible for removal or replacement costs, local repair costs, transportation costs, or contingent expenses
incurred without our prior approval.
THIS WARRANTY IS EXPRESSLY IN LIEU OF ANY AND ALL OTHER WARRANTIES AND
REPRESENTATIONS, EXPRESSED OR IMPLIED, AND ALL OTHER OBLIGATIONS OR
LIABILITIES ON THE PART OF RKI INSTRUMENTS, INC. INCLUDING BUT NOT
LIMITED TO, THE WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. IN NO EVENT SHALL RKI INSTRUMENTS, INC. BE LIABLE
FOR INDIRECT, INCIDENTAL, OR CONSEQUENTIAL LOSS OR DAMAGE OF ANY KIND
CONNECTED WITH THE USE OF ITS PRODUCTS OR FAILURE OF ITS PRODUCTS TO
FUNCTION OR OPERATE PROPERLY.
This warranty covers instruments and parts sold to users by authorized distributors, dealers, and representatives
as appointed by RKI Instruments, Inc.
We do not assume indemnification for any accident or damage caused by the operation of this gas monitor, and
our warranty is limited to the replacement of parts or our complete goods.
a) Absorbent cartridges d) Batteries
b) Pump diaphragms and valves e) Filter elements
c) Fuses

65-2643RK-05-04 M2A Transmitter Operator’s Manual
Table of Contents
Chapter 1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
About the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
About this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Chapter 2: Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
External Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Internal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Chapter 3: Installation & Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Mounting the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Wiring the M2A Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Chapter 4: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Information Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4 - 20 mA Signal Output Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Alarm Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Chapter 5: Configuration Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Viewing & Changing M2A Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Chapter 6: Gas Type Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Selecting the Gas Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

65-2643RK-05-04 M2A Transmitter Operator’s Manual
Chapter 7: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Calibration Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Replacing Components of the Oxygen Detector . . . . . . . . . . . . . . . . . . . . . . . . . 38
Chapter 8: RS-485 Modbus Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Wiring the M2A in a Modbus System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Using the M2A in a 4-wire Modbus System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Modbus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Supported Modbus Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Chapter 9: Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Appendix A: Control Button Quick Reference Guide. . . . . . . . . . . . . . . . . . . . . . . . . 51
Appendix B: PLC and DCS Device Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Appendix C: Function Code 16 Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

6 65-2643RK-05-04 M2A Transmitter Operator’s Manual
Chapter 1: Introduction
Overview
This chapter briefly describes the 65-2643RK-05-04 M2A Transmitter. This chapter also describes the 65-
2643RK-05-04 M2A Transmitter Operator’s Manual (this document). Table 1 at the end of this chapter lists the
specifications for the M2A.
About the M2A Transmitter
The M2A transmitter is a fixed mount, continuous-monitoring detector head. All user adjustable parameters may
be accessed using push button switches. In addition, calibration may be performed non-intrusively by use of a
magnetic wand accessory which activates magnetic switches through a window at the front face of the detector
head.
The M2A displays the current gas reading on an OLED display which is visible through the window in the cover
(front face) and provides a 4 - 20 mA signal which indicates the target gas reading for use by a gas monitoring
controller, recording device, or programmable controller. The M2A also provides an RS-485 Modbus output.
Three sets of relay contacts, two controlled by the gas alarms and one by the fail alarm, rated at 115 VAC 5 amps
are available for controlling devices such as lights or horns or for controlling higher rated relays.
Four operating modes allow you to display and change setup and calibration settings and change the gas type.
They are Calibration Mode, Configuration Mode, Gas Type Mode, and Modbus Mode.
About this Manual
The M2A Transmitter Operator’s Manual uses the following conventions for notes, cautions, and warnings.
NOTE: Describes additional or critical information.
CAUTION: Describes potential damage to equipment.
WARNING: Describes potential danger that can result in injury or death.

65-2643RK-05-04 M2A Transmitter Operator’s Manual 7
Specifications
Table 1 lists specifications for the M2A.
WARNING: When using the M2A, you must follow the instructions and warnings in this manual to
assure proper and safe operation of the M2A and to minimize the risk of personal injury. Be
sure to maintain and periodically calibrate the M2A as described in this manual.
Table 1: M2A Specifications
Target Gas/Detection Range Oxygen: 0 - 25.0% volume, 0.1% increments
Alarm Settings (Alarm 1/Alarm 2)* 19.5% volume (decreasing)/23.5% volume (increasing)
Construction (housing) Explosion-proof junction box, NEMA 4X
Area Classification Explosion-proof for Class I, Groups B, C, and D
Sampling Method Diffusion
Input Power 10 - 30 VDC
Controls • Three push button switches
• Three magnetic switches for non-intrusive calibration
Weight 5.5 lbs.
Signal Output • 4 to 20 mA with impedance maximums listed below
-12 VDC: 500 ohms impedance max
-24 VDC: 1000 ohms impedance max
• RS-485 Modbus
Operating Temperature -20°C to 45°C
Accuracy ± 0.5% O2
*These are the RKI factory settings. You can change the alarm settings in Configuration Mode.
See “Viewing & Changing M2A Parameters” on page 27.

8 65-2643RK-05-04 M2A Transmitter Operator’s Manual
Chapter 2: Description
Overview
This chapter describes the components of the M2A transmitter. The transmitter is a 4 - 20 mA type detector head.
It consists of the oxygen detector, calibration adapter/splash guard, terminal PCB, the M2A junction box, and the
detector junction box. The two-junction-box configuration is intended for situations where the detector needs to
be installed at an inaccessible location. The detector junction box can be installed at the inaccessible location and
the M2A junction box can be installed in a more readily accessible area.
External Description
This section describes the junction boxes and all external components of the M2A transmitter.
Figure 1: M2A External Components
3/4 NPT Conduit Hub Terminal
Strip
Magnetic
Wand
3/4 NPT
Conduit Hub
Oxygen Detector
Detector
Junction Box
M2A
Junction
Box
Calibration Adapter/
Splash Guard
3/4 NPT
Conduit Hub
Window
Mounting Slot (2x)

65-2643RK-05-04 M2A Transmitter Operator’s Manual 9
M2A Junction Box
The M2A’s cast aluminum junction box is dust and weather resistant. The junction box also protects the M2A
and all connections made to it. Use the three 3/4 NPT conduit hubs to wire the remotely installed combustible gas
detector and connect wiring from an external device, typically an RKI controller. The top hub is shipped with a
factory installed and sealed conduit plug to avoid leaks into the junction box. If necessary, the conduit plug can
be removed and the top hub can be used for wiring.
WARNING: If the top conduit hub is used for wiring, be sure to seal the threads to ensure water does not
enter the junction box. See “Wiring the M2A Transmitter” on page 17 for complete wiring
instructions.
Use the junction box’s two mounting holes to mount the M2A to a vertical surface at the monitoring site. The
window in the cover on the front of the junction box allows you to view the OLED display and use the magnetic
wand to actuate the magnetic control switches so you can perform non-intrusive calibration. Removing the cover
allows you to access the interior of the junction box.
Detector Junction Box
The detector junction box is intended to be installed remotely from the M2A junction box. The oxygen detector
is factory installed in the bottom 3/4 NPT conduit hub. A terminal strip is provided for wiring connections and
the detector is factory wired to one side of this terminal strip. The other side of the terminal strip is for user-
supplied wiring to the detector terminal strip located in the M2A junction box. This wiring should go through the
top 3/4 NPT conduit hub. Three spacers installed on the back of the junction box controls the distance of the
junction box from a mounting surface. A ground boss near the top conduit hub provides an external earth ground
connection.
Oxygen Detector
The oxygen detector consists of the detector housing body, detector housing cap, cap gasket, and the plug-in
sensor.
Figure 2: Oxygen Detector Component Location
Flame Arrestor
Guard
Detector Housing Cap
Oxygen Sensor
Detector Housing Body
Cap Gasket

10 65-2643RK-05-04 M2A Transmitter Operator’s Manual
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 oxygen detector into the 3/4 NPT hub on the bottom of the detector junction
box. Two wires extend from the top of the detector housing body. Use these wires to connect the oxygen detector
to the terminal strip. One of the wires is green and one of the wires is white.
The housing includes a two-socket pattern. This socket pattern accepts the sensor’s two 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 from damage. Unscrew the detector cap to access the plug-
in sensor for maintenance or replacement. A cap gasket seals the interface between the housing and cap. A flame
arrestor guard is permanently bonded to the cap.
Plug-In Oxygen Sensor
The sensor is secured within the detector assembly by the housing cap. Through a series of chemical and
electrical reactions, the sensor produces an electrical output that corresponds to the detection range of the
transmitter.
Calibration Adapter/Splash Guard
A calibration adapter/splash guard is installed on the oxygen detector. A fitting at the bottom of the calibration
adapter/splash guard allows a length of tubing to be connected for calibration and routed to a more easily
accessible location (near the M2A junction box is optimal for ease of calibration). The calibration adapter/splash
guard also protects the detector from splashing water or direct water spray.
Magnetic Wand
The magnetic wand is a short plastic rod with a magnet in one end. It is used to actuate the magnetic control
switches on the control PCB while the junction box cover is still installed so that non-intrusive calibration can be
performed.