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RKI Instruments M2A CT-7 Style Sensor / Transmitter, Ammonia (NH3) 0 - 500 ppm, non explosion proof with j-box - 65-2670-NH3-5

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RKI Instruments
RKI Instruments M2A CT-7 Style Sensor / Transmitter, Ammonia (NH3) 0 - 500 ppm, non explosion proof with j-box - 65-2670-NH3-5
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RKI Instruments M2A CT-7 Style Sensor / Transmitter, Ammonia (NH3) 0 - 500 ppm, non explosion proof with j-box - 65-2670-NH3-5

RKI Instruments M2A CT-7 Style Sensor / Transmitter, Ammonia (NH3) 0 - 500 ppm, non explosion proof with j-box - 65-2670-NH3-5


65-2670-NH3-5 M2A CT-7 Style Sensor / Transmitter, Ammonia (NH3) 0 - 500 ppm, non explosion proof with j-box by RKI Instruments

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
  • Available gases include LEL, O2, H2S, CO, CO2, and 100% Vol 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)

*Please note we can only ship RKI products to customers within the United States

Hydrogen Sulfide
Carbon Monoxide
Arsine (AsH3)
Ammonia (NH3)
Phosphine (PH3)
Hydrogen Cyanide (HCN)
Sulfur Dioxide (SO2)
Carbon Dioxide
Galvanic cell
Measuring Ranges
0-25% Vol.
0-100 ppm
0-300 ppm
0 - 1.5 ppm
0 - 75.0 ppm
0 - 1.00 ppm
0 - 15.0 ppm
0 - 6.00 ppm
0 - 5000 ppm
0 - 5% Vol.
0 - 50% Vol.
0 - 100% Vol.
0.1% Vol.
1 ppm
0.01 ppm
0.1 ppm
0.01 ppm
0.1 ppm
0.01 ppm
20 ppm / 0.1% Vol. / 1% Vol.
Lower Detectable Limit (LDL)
0.1% Vol.
2% of full scale
Response Time (T-90)
35 Seconds or less
60 Seconds or less
30 Seconds or less
Max Current Draw (24VDC)
125 mA with alarm 1 and alarm 2 active and all relays energized
Life Expectancy
2 to 3 years with normal service
Accuracy (which ever is greater)
± 0.5% Vol. O2
± 5% of reading or ± 2 ppm H2S
± 5% of reading or ± 5 ppm CO
± 10% of reading or ± 5% of full scale
± 5% of reading or ± 2% of full scale
Alarm Settings
Two fully programmable alarm set points, increasing / decreasing, latching / self-resetting, on delays, off delays, normally energized or de-energized
Alarm Indication
Visual LEDs. Alarm 1=Amber; Alarm 2=Red; Fail=Red
5 Amp form 'C' contacts for alarm 1, alarm 2, and fail
Height: 8.5" (215 mm), Width: 5.2" (132 mm), Depth: 4.5" (114 mm)
Alphanumeric OLED display. 8 characters per line; 2 lines for gas concentration readout, plus user-friendly calibration and setup
Sensor Rating
Non explosion proof construction, designed for Class I, Div. 2, Groups B, C, D (no certification)
Housing J-Box
NEMA 4X, explosion proof, watertight, cast aluminum with o-ring seal and epoxy powder coating
Magnet used for calibration functions. Calibrates without opening the housing. Internal push-button controls also available for calibration and setup.
Aluminum / Plastic (non explosion proof)
Operating Environment
Operating Temperature
-4°F to 113°F
-20°C to 45°C
-40°F to 104°F
-40°C to 40°C
23°F to 104°F
-5°C to 40°C
14°F to 104°F
-10°C to 40°C
-40°F to 122°F
-40°C to 50°C
Relative Humidity
5 - 95% RH non-condensing
Indoor or outdoor
Operating Voltage
10 VDC - 30 VDC
Linear 4-20 mA signal, into 1000 ohms impedance max (24DC), 0 - 500 ohms max (12VDC) corresponding to 0 - full scale
Modbus RTU output standard, fully configurable, 2-wire RS-485, 1200 to 19.2k baud
Compatible with all RKI Beacon controllers, as well as most DCS / PLC systems: Beacon 110, Beacon 200, Beacon 410, Beacon 800
One year materials and workmanship

Datasheets & User Manuals

Questions & Answers