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S2 Series

The RKI S2 series gas sensor transmitters are highly reliable and cost effective basic 4-20 mA transmitters for the detection of common gas hazards. The S2 series transmitters are available for LEL (catalytic), LEL (IR) CH4, LEL (IR) HC, C02 (IR), ppm H2 (MOS) and ppm Hydrocarbons (MOS). The electronics are encased inside a potted package to avoid damage from mechanical abuse or corrosion, and this assembly is installed inside an explosion-proof enclosure. All sensors are explosion-proof with flame arrestors and approved for use in hazardous atmospheres.

The only tools required to calibrate the S2 series are a voltmeter, screwdriver, and cal gas. The zero and calibration functions are performed by adjusting potentiometers on the amplifiers. The amplifier has test jacks for connecting to a voltmeter for calibration purposes, and the sensor response is viewed on the voltmeter as a 100 mV to 500 mV signal. Field calibration can be performed easily and quickly by one person.

The S2 series transmitters can be used either indoors or outdoors. The flame arrestors utilize a patented coating which make them water repellent, and splash guards are also available for use in very wet environments.

The transmitter operates from 24 VDC, and provides a 4-20mA signal which can be connected to a wide variety of controllers.

  • Features
  • Applications
  • Specification
  • Accessories
  • Explosion Proof Housing
  • Patented Water repellent Sensor Coating
  • Available for LEL, H2, H2S, CO, O2, ppm HC, and CO2
  • IR Sensors available for LEL & CO2
  • H2 Specific LEL and ppm versions available
  • Long Life Sensors (2 + years typical)
  • Competitively Priced
  • UL or CSA Approved
  • Petrochemical Plants
  • Refineries
  • Gas Plants
  • Offshore Drilling Platforms
  • Water & wastewater treatment plants
  • Pulp & Paper mills
  • Gas, Telephone, & Electric Utilities
  • Parking Garages
  • Manufacturing Facilities
  • Steel
  • Automotive
  • Chemical Storage Buildings
  • Battery Charging (H2)
Model LEL (General Purpose) LEL H2 Specific O2 H2S CO MOS Infrared
Part # 65-2405RK
65-2451 RK-05
65-232ORK- 100
65-2428RK-05 65-2438RK-Q5 65-2442R K-1000
65-2461 RK-500 65-2391 RK-03 65-2390RK-CH4 65-2390RK-HC
Measuring Range 0-100% LEL 0-100% LEL
(H2 Specific)
0-25% Vol
0-100% Vol
0-100 ppm 0-300 ppm 0-1000 ppm / 0-2000 ppm 0-500 ppm HEX 0-5% Vol. 0-100% LEL
Max Current Draw (24VDC 200 mA (power wires) 25 mA
(signal wires) 3 wires
20 mA max, 2 wires 200 mA (power wires) 25 mA
(signal wires) 3 wires
60 mA (power wires)
25 mA (signal wires) 3 wires
Outputs 4 - 20 mA signal
Response Time (T-90) 30 seconds 20 seconds 20 seconds 45 seconds 30 seconds 45 seconds to 90% 30 seconds to 90%
Operating Environment
Location Indoor/outdoor. Explosion proof for Class I, Div 1, Groups B, C, and D. Indoor/outdoor. Explosion proof for Class I, Div. 1, Groups B, C, and D. Indoor or outdoor. Explosion proof for Class I, Div. 1, Groups B, C, and D.
Temperature -40 10 185° F -4 to 122° F 4 to 122° F
Humidity o - 99% RH, non condensing
Housing Aluminum explosion proof enclosure
Life Expectancy 1 to 2 years with normal sensor exposure to flammable gas. 3-5 Years for H2 exposure 2-3 years with normal service 5 years normal service
Zero Sets transmitter output to 4 mA with zero output from sensor
Span Sets transmitter output to 20 mA with full scale output from sensor
Operating Voltage 11 VDC to 30 VDC *19-30VDC (250 OHMS impedance max) 19 VDC to 30 VDC 11 VDC to 30 VDC
Approvals 65-2451 RK UL
65-2451 RK UL
C CSA us
65-2451 RK UL
65-2452RK UL
65-2451 RK-05
C CSA us
Warranty One year materials and workmanship

*Consult factory regarding higher impedance circuits

Specifications subject to change without notice

  • AC Power Supply
  • Remote Horns & Lights
  • Calibration Kits
  • Calibration Adaptors
  • Splash Guards
  • Flow through Adaptors
  • Data Loggers
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