Explosion Proof

M2A Series Explosion Category

The RKI M2A™ is a state-of-the-art transmitter that can operate as an independent, stand-alone monitor or as part of an integrated system. The M2A connects with an analog or digital signal to virtually any controller, PLC, or DCS. Setup procedures are simplified with user friendly push buttons and OLED menus. It utilizes a magnetic wand technique for performing non-intrusive calibration. The M2A provides an automatic zero drift correction feature, which results in more stable readings and reduces the need for adjustments due to sensor aging.

The housing of the M2A does not need to be opened for zeroing or calibration, making it unnecessary to declassify the area for routine maintenance. It is designed so that a complete field calibration can be performed by one person. Sensor construction is rated Class I, Div. 1 Groups B, C, D for flammables, CO, H2S, O2, and CO2, and Class I, Div. 2 for all other toxics.

The transmitter provides a 4-20 mA output in addition to a Modbus digital output. It also has two levels of alarms with relays, plus a fail alarm with relay. A digital display of the gas concentration, as well as alarm and status lights, can be viewed through the front window.

The toxic sensors are electrochemical type plug-in sensors, which provide high specificity, fast response, and long life. The plug-in design allows quick replacement in the field with no tools required. Toxic sensors are designed for use in Class I, Div. 2 hazardous locations. Sensors available for NH3, SO2, PH3, AsH3, and HCN.

The M2A represents the latest leading edge technology in sensor / transmitters today.

  • Operates with or without a controller
  • Direct digital readout with OLED cold temperature display
  • LEL, O2, H2S, CO, CO2,
    • 100% Vol CH4, and 0-9,000 PPM CH4
    • Toxic Gases include NH3, SO2, HCN, and more
  • Infrared sensor for combustibles and CO2
  • 4-20 mA & digital Modbus outputs standard
  • 2 fully programmable alarm relays & fail relay
  • Non-intrusive calibration via magnetic wand
  • Explosion proof construction
  • Patented water repellent sensor cover
  • User friendly setup, push buttons & OLED menus
  • Long-life sensors (2+ years typical)
  • Petrochemical plants
  • Refineries
  • Water & wastewater treatment plants
  • Pulp & paper mills
  • Manufacturing facilities
  • Automotive
  • Semiconductor plants
  • Chemical plants
 Combustibles (LEL)Combustibles (PPM)LEL (H2 Specific)O2 (Oxygen)H2S (Hydrogen Sulfide)CO (Carbon Monoxide)CH4 (Methane)HC (Hydrocarbons)CO2 (Carbon Dioxide)
Part #65-2640RK65-2647RK65-2641RK65-2643RK-0565-2645RK-0565-2646RK-0565-2649RK-CH465-2649RK-HC65-2660RK-02
SensorsCatalyticGalvanic cellElectrochemicalInfrared
Measuring Ranges0 - 100% LEL0 - 9000 ppm CH40 - 100% LEL0 - 25.0% Vol.0 - 100 ppm0 - 300 ppm0 - 100% LEL0 - 100% LEL-02: 0 - 5000 ppm
0 - 100% Vol.-03: 0 - 5% Vol.
-05: 0 - 50% Vol.
-10: 0 - 100% Vol.
Resolution1% LEL20 ppm1% LEL0.1% Vol.1 ppm1% LEL / 1% Vol.20 ppm / 0.01%
Vol / 0.1% Vol. /
1% Vol.
Lower Detectable
Limit (LDL)
2% of full scale0.1% Vol.2% of full scale
Max Current Draw (24VDC)160 mA with alarm 1 and alarm 2 active and all relays energized125 mA with alarm 1 and alarm 2 active and all relays energized160 mA with alarm 1 and alarm 2 active and all relays energized
Response Time (T-90)35 Seconds or less90 Seconds or less60 Seconds or less90 Seconds or less30 Seconds or less
Life Expectancy2 to 3 years with normal service3 to 5 years with normal service2 to 3 years with normal service5 years plus with normal service
Accuracy (which ever is greater)± 5% of reading or ± 2% of full scale± 0.5% Vol. O2± 5% of reading or ± 2 ppm H2S± 5% of reading or ± 5 ppm CO± 5% of reading or ± 2 % of full scale
Weather ResistantPatented water repellent sensor coating
Alarm SettingsTwo fully programmable alarm set points, increasing / decreasing, latching / self-resetting, on delays, off delays, normally energized or de-energized
Alarm IndicationVisual LEDs. Alarm 1, Amber; Alarm 2, Red; Fail, Red
Relays5 amp form ‘C’ contacts for alarm 1, alarm 2, and fail
DimensionsHeight: 8.5” (215 mm)
Width:5.2” (132 mm)
Depth:4.5” (114 mm)
DisplayAlphanumeric OLED display. 8 characters per line; 2 lines for gas concentration readout, plus user-friendly calibration and setup
EnclosureExplosion proof for Class I, Div 1, Groups B, C, D.
Enclosure RatingNEMA 4X, explosion proof, watertight, cast aluminum with o-ring seal and epoxy powder coating
ControlsMagnet used for calibration functions. Calibrates without opening the housing. Internal push-button controls also available for calibration and setup.
Operating Environment
Operating Temperature-40°F to 167°F-4°F to 113°F-40°F to 104°F23°F to 104°F-40°F to 122°F
-40°C to 75°C-20°C to 45°C-40°C to 40°C-5°C to 40°C-40°C to 50°C
Relative Humidity5 - 95% RH non-condensing
LocationIndoor or outdoor. Explosion proof for Class I, Div. 1, Groups B, C, D.
Operating Voltage10 VDC - 30 VDC
AnalogLinear 4-20 mA signal, into 1000 ohms impedance max (24DC), 0 - 500 ohms max (12VDC) corresponding to 0 - full scale
DigitalModbus RTU output standard, fully configurable, 2-wire RS-485, 1200 to 19.2k baud
Approvals65-2640RK: UL65-2641RK: ULC CSA USC UL US
65-2640RK-05: C CSA US65-2641RK-05: C CSA US
ControllersBeacon 110, Beacon 200, Beacon 410A, Beacon 800 as well as most DCS / PLC systems
WarrantyOne year material and workmanship

M2A Wiring Matrix
Number of Wires to ControllerMaximum Distance to Controller
18 AWG wire16 AWG wire14 AWG wire
32500 ft.5000 ft.8000 ft.