Infrared Combustible Gas Sensor Module 5100-28-IT

Infrared Combustible Gas Detector 5100-28-IT

Sierra Monitor’s infrared fixed gas detector, the 5100-28-IT, monitors combustible gases such as Methane and Propane, detecting and alarming users when gases reach between 0 to 100% lower explosive limit (LEL) concentrations. 

The 5100-28-IT detector is based on infrared (IR) technology, an accurate and stable method of detection that requires low maintenance and can operate in highly combustible gas and/or low oxygen environments.

infrared gas detector

As the industry-wide top choice network-enabled fixed gas detector, the FM-approved 5100-28-IT detector utilizes Non-Dispersive Infrared technology to monitor for combustible gases. This technology also allows the detector to rapidly recover after exposures to high concentrations of hydrocarbon gas and operate in environments where catalytic bead poisons might exist. The detector also has minimal maintenance requirements and only requires one-year calibration intervals. Although the 5100-28-IT detector can be used as a stand-alone sensor, it can also be used as a 4-20 mA component or as a Modbus RTU node. For higher level system capability, the detector can interface directly to Sierra Monitor’s Sentry IT Controller to enable system level Modbus serial communications, area, and zone alarm management, extensive system diagnostic features, WebServer interface, and multiplexing sensor connections.

The fixed Infrared Combustible Gas Detector 5100-28-IT is approved and certified by a variety of third-party agencies, including UL, FM, SIL-2, ATEX, CSA, and ABS. These approvals and certifications assure our customers that we carry only the highest quality of products.


The 5100-28-IT supports GlobalCal™, our unique global calibration feature of the Sentry IT Controller. This allows a single technician to calibrate connected detectors from the Sentry IT Controller. With GlobalCal, the calibration happens at the controller level. Multiple detectors can be connected to a single controller, allowing groups of sensors to be calibrated at the same time. Standard gas is applied remotely, using permanently installed tubing, rather than direct delivery to the fixed gas detector.

Combined with the one-year calibration interval, GlobalCal reduces labor costs associated with calibration. The need to shut down active process areas for calibration consequently costs facilities thousands of dollars in lost production time. GlobalCal, with its remote and non-intrusive methods, allows production to continue during the calibration process, thus avoiding the costs of lost production. In addition, factory-authorized service technicians performing gas detector calibration save time and costs by remotely calibrating all gas detectors at once from the Sentry IT Controller.

GlobalCalTM support

Non-intrusively calibrate all connected sensors at the same time without declassifying the area

Network compatible with Modbus, 4-20mA, HART, relay interface

Easily install in a variety of field applications and easily obtain critical safety information wherever needed

Menu-driven system

Rapidly adjust user-friendly configuration of alarm setpoints, calibration, maintenance, and alarm acknowledgment

Modbus RTU Serial Interface

Provide an easy interface to the world's most common industrial protocol

Integral LED Display

Easily calibrate and access gas concentrations, relay statuses, and diagnostics

SMC Sentry Digital Bus Interface

Connect easily with existing Sentry systems that have been in operation for many years

1 Year Calibration Interval

Dramatically reduce maintenance and operating costs for the user

Stainless Steel 316 or Epoxy-Coated Aluminum enclosures

Meet specific installation needs with different enclosure materials

Internal Continuous Self-Diagnostics

Automatically indicate any fault or optics problems

Model Number


Sensor Type

Infrared, Dual Wavelength



  • Dual Range:
  • Default: 0-100% LEL Methane
  • User Setting: 0-100% by vol. Methane
  • Repeatability: +/- 1% LEL
    • +/- 1% for 0-50% LEL range
    • +/1 2% for 51-100% LEL range
  • Zero Drift: +/- 1% full scale per month @ 20 oC (68oF) ambient (max +/- 3% full scale per year)
  • Sensor Life: Typically >5 years
  • Heated Sensor: Heated cell to prevent condensation
  • Response Time: T90 < 10 sec*

Display: Fixed and scrolling LED

Signal Output:

Sentry digital bus

Analog 4-20 mA Linear

3-wire Non-Isolated

4-wire Isolated

Serial RS-485 Modbus RTU

Relay: Optional



  • 5 amp Alarm, Warning (0.25 amp Trouble)
  • 5A @ 250 VAC, 5A @ 30 VDC (Alarm, Warning)
  • Board includes auxiliary connection for Sentry multiplexing

HART: Termination board includes HART, Modbus RS-485, 4-20mA, Digital Input, 2A Relay output,

No Sentry bus

Remote Sensor: Up to 100 feet (30.4m)


Power consumption: 3 watts

Input voltage: 24 VDC nominal: 10-30 VDC

Operating Range

Ambient Temperature Range: -40o to 140oF (-40° to 60°C)

Relative Humidity: 0-99% Non-Condensing

  • Dimensions (H x W x D)
    • A1 & A2: 7.8 x 5.7 x 3.9 in. (19.8 x 14.5 x 9.9 cm)
    • S1 & S2: 7.5 x 4.4 x 4.9 in. (19 x 11 x 12 cm)
  • Weight
    • A1 & A2: 3.4 lb. (1.5 Kg)
    • S1 & S2: 7.2 lb. (3.3 Kg)
  • Enclosure: Epoxy coated aluminum or 316 stainless steel
  • Housing: AL or SS (same as enclosure)
  • Hazardous Area Classification:
    • Explosion proof, Class 1, Div. 1, Groups C, D
    • Class I, Zone 1
    • Group IIC, IP66, IP65, NEMA 4X, T6
    • TA = -40oC to 85oC II2 GD, Ex d IIC Warranty: 2 years

UL-2075: Performance Approved

ATEX II G, Ex d IIB+H2 T6 Gb, Ta = -20 oC to 60oC

FM Approval 6320: Combustible Gas Detector Performance

FM Approval 3600: Class I Div. 1, Groups C, D

SIL-2 Certified: Certified by Lloyd’s Register (IEC 61508)

CSA: For enclosure in hazardous locations

ABS: Certificate of Compliance

CCCF/CQST: Certificate for China

CCOE/PESO: Certificate for India

Sentry IT Fire and Gas Detection Solutions

A brief introduction to the sales, design and manufacturing facilities for Sierra Monitor Corporation's Sentry IT fire and gas solutions.

How to Easily Calibrate Sentry IT Gas Sensors with GlobalCal

A video demonstration on how to perform GlobalCal, the simple and time-saving calibration procedure, on all Sentry IT gas sensor modules.