Model 902 – Digital Toxic Gas Detector

Digital Toxic Gas Detector

Model: 902

1.0       Application

Model 902 are digital gas detectors for CO-carbon-monoxide and NO₂ –nitrogen-dioxide concentration monitoring. They are widely used in large vehicle exhaust environment like in-door parking garages or municipal work facilities, warehouses, etc. to monitor concentrations of CO or NO₂.

2.0          Working Principle

Simplified Schematic

3.0       Features

• 3 color LEDs indicate communication status, concentration level and trend/numerical display (optional)
• Automatic calibration reminder
• Sensor “End of Life” warning
• Hardware watchdog for high reliability and fail safe operation

4.0       Specification

• Detectable gases: CO or NO₂
• Inputs: Two sensors maximum – one local, one remote (4-20mA input).
• Outputs: Modbus RTU, 4-20mA, relay output (standalone version)
• Wiring: 4 Wire ‐ 2 power + 2 communication
• Connection: RS‐485
• Enclosure: PVC
• Supply Voltage: 16‐42 VDC, 12‐32 VAC
• Dimensions: 4” x 4” x 25”
• Operating temperature: ‐20°C to 50°C (‐4°F to 122°F)
• Warranty: 2 years (sensors excluded)
• Indicators: LCD for gas concentration, LEDs for sensor, transceiver operation and fault
• Coverage area: 7500 sq. ft. (50’ radius)
• Recommended mounting height: 4‐5’F.F.

4.1 Carbon Monoxide Sensor for 902‐CO

• Range: 0‐250ppm
• Sensor type: Electrochemical
• Accuracy: 1ppm
• Response time: Better than 30 Seconds to 90%
• Life expectancy: 6 years
• Operating humidity: 5‐95% RH Non‐Condensing

4.2 Nitrogen Dioxide Sensor for 902‐NO2

• Range: 0‐10ppm
• Sensor type: Electrochemical
• Accuracy: 0.1ppm
• Response time: Better than 25 Seconds to 90%
• Life expectancy: Better than 2 years
• Operating humidity:   5‐95% RH Non‐Condensing