D12-IR Combustible, CO2 or N2O Gas Transmitter


ATI’s D12-IR gas transmitter product line has been expanded. Now available in this versatile package is an LEL transmitter utilizing an Infrared sensor that resists the poisoning problems inherent in catalytic bead sensors. The D12-IR utilizes a compact IR sensor in a corrosion resistant housing with sintered flame arrestor to meet hazardous area classification requirements and is suitable for most plant environments.

The D12-IR gas transmitter eliminates the poisoning problems inherent in catalytic bead sensors. While catalytic LEL sensors offer reliable service, the presence of silicon vapors, hydrogen sulfide and halogenated hydrocarbons can quickly degrade sensor performance. Infrared sensing technology is not susceptible to these potential interferants which means greater measurement stability and longer sensor life.

The D12-IR transmitter can also be configured with Infrared sensor for carbon dioxide (CO2) or nitrous oxide (N20) detection. All sensor versions can operate in diffusion mode for ambient air or with a flow cell for pumped samples.

The D12-IR gas transmitter is available in four configurations:

  • For measurement and data transmission to remote display and alarm equipment, the D12-IR operates in 3 wire mode. Integral LCD indicates gas concentration as well as alarm conditions
  • Transmitter with HART for plants operating with HART protocol communications systems, the D12-IR can be supplied with this option. The HART output supports both 4-20 mA and constant current mode of operation.
  • Transmitter with integral relays for systems requiring local alarm functions or systems where discrete outputs are desired, the D12-IR can provide 3 relay outputs. Relays are assignable to any alarm setpoint or fault condition and are fully programmable for setpoint, hysteresis and time delay.
  • When RS-485 communication is desirable, D12-IR transmitters with alarm relays can be supplied with a Modbus interface. software supports up to 247 unique addresses for large system use.


  • Infrared sensing element is protected inside a stainless steel assembly with a sintered stainless steel flame arrestor.
  • Because the IR sensor is always in an active state, the transmitter continuously monitors critical sensor functions and indicates any sensor problems both on the display and through the analog output.
  • D12-IR transmitters can be factory calibrated for volumetric methane measurements in special applications. Ranges from 0-10%, to 0-100% by volume are available. A separate sensor is also available for high percent level measurements of heavier hydrocarbons such a butane and propane.
  • Each time a sensor is zeroed or spanned the data is stored in memory. Calibration history can be recalled and sensor condition reviewed by operating personnel when necessary.
  • Optional relays outputs can be used for local alarm functions. All relays are programmable for setpoint, hysteresis, on-delay, off-delay and other variables. Even a remote reset feature is provided for in the transmitter design.
  • Transmitter analog output can be set to user definable values. This provides for complete loop testing without the need to apply gas to the sensor
  • Alarm relays may be activated on command to allow testing of local alarm devices. Any combination of relays may be activated based on operator selection. Output and alarms may also be inhibited for maintenance and calibration.
  •  The transmitter is available with either HART or MODBUS protocol. The HART protocol supports the HART Universal and Common Practice Commands at 1200 baud using the Bell 202 FSK modem standard. The MODBUS protocol supports 9600 baud access to concentration and status information and supports alarm setup and many other functions on either RS485 or RS232 (software selectable). Comes with a register/tag database on a 3 1/2″ diskette.
  • Gas concentrations are displayed in large, easy to read numbers. The display also provides alarm indication and complete menus for setting up operating parameters. A back light is available.
  •  Measured gas values are stored at user definable intervals and can be recalled when needed on the LCD display. Data can be downloaded using an MODBUS interface.
  • Each time a sensor is zeroed or calibrated, the data is stored in memory. Calibration history can be recalled and sensor condition reviewed by operating personnel whenever necessary.
  • Operating functions such as calibration, alarm setup, alarm reset, data view and setup options are all available using a magnetic tool. It is never necessary to open the enclosure when making adjustments.
  •  Program settings stored in the transmitter may be protected by a user selectable password. Operators may still review all function, but changes may only be made by authorized personnel.
  • Transmitter analog output can be set to user definable values and relay outputs can be set to specific states for complete simulation of detection system operation. Output and alarms may also be inhibited for maintenance and calibration.
  • The D12 electronic assembly plus easily into a terminal board in the base of the enclosure. Transmitters can be easily removed for wiring and quickly replaced in the event of a fault condition.
  • Transmitters are designed for operation in hazardous areas. The cast aluminum housing for the D12 transmitter is rated for Class 1, Division 1 Group B, C, D locations and is UL, FM and CSA certified.


Sensor Type Single path non dispersive infrared
Sensor Separation Maximum 25′ cable from sensor to transmitter
Range Combustible Gas: 0-50% LEL min, 0-100% max
Volumetric Methane: 0-10% min, 0-100% max
Carbon Dioxide: 0-2,000 ppm, 0-50% max
Nitrous Oxide: 0-2,000 ppm, 0-1% max
Accuracy +/-5% of value, but limited by available calibration gas accuracy
Gases Available Combustible gas, carbon dioxide or volumetric methane. Combustible gas selectable for methane, propane or butane Consult factory for other gases and vapors.
Response Time T90 < 10 seconds
Electronic Repeatability ± 1%
Electronic Linearity ± 0.5%
Zero Drift Less than 1% of full scale per month, non cumulative
Span Drift Dependent on operating environment but generally less than 1% per month
Serial Interface Hart (1200 baud modem interface)
MODBUS (1200-9600 – RS232 or RS485 s/w selectable)
Optional Alarm Relays Three SPST, 5 A @ 230 VAC resistive
Relay Coil Programmable either normally energized or normally de energized
Analog Output Powered at 4-20mA, 675 ohms maximum at 24 VDC
Power 12-30 VDC, 350 mA maximum (3W average)
Temperature Limits -40 to 75°C
Controls 4 magnetic switches on front of transmitter
Enclosure Class 1 Div 1, Groups B, C & D
Weight 4 pounds

Ordering Information

Many other combinations available, for pricing, please call AFC International at 1-800-952-3293, 219-987-6825 or fax 219-987-6826 or email sales@afcintl.com.

Catalog No.
D12 Gas Transmitter for Combustibles, 0-100% by Volume, no relays
D12 Gas Transmitter for High Hydrocarbons 100% by Volume, no relays D12-IR-1-2-1
D12 Gas Transmitter for CO2, 0-2000 ppm or 0-5% by Volume, no relays D12-IR-1-3-1
D12 Gas Transmitter for CO2, 0-5% or 0-50% by Volume, no relays D12-IR-1-4-1


D12-IR gas transmitter literature

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