The CJMCU-6814 Gas Sensor Module is a multi-gas detection breakout board built around the SGX Sensortech MiCS-6814 MEMS sensor. Designed with three fully independent sensing channels on a single chip, Reducing (RED), Oxidizing (OX), and Ammonia (NH3), it simultaneously detects a wide spectrum of environmental pollutants, vehicle exhaust fumes, industrial gases, and agricultural odours.

Specifications

• Sensor IC: SGX Sensortech MiCS-6814 MEMS Gas Sensor
• Operating Voltage: 5V DC
• Heating Power Consumption: ~450mW total
• Sensing Architecture: Silicon MEMS micro-diaphragm with integrated heating resistors
• Sensing Channels: 3 Independent Channels (RED, OX, NH3)
• Operating Temperature: -30°C to +85°C
• Operating Humidity: 15% to 95% RH (Non-condensing)

Detectable Gases and Concentration Ranges

• Carbon Monoxide (CO): 1 to 1000 ppm (RED Channel)
• Nitrogen Dioxide (NO2): 0.05 to 10 ppm (OX Channel)
• Ethanol (C2H5OH): 10 to 500 ppm (RED Channel)
• Hydrogen (H2): 1 to 1000 ppm (RED Channel)
• Ammonia (NH3): 1 to 500 ppm (NH3 Channel)
• Methane (CH4): >1000 ppm (RED Channel)
• Propane (C3H8): >1000 ppm (RED Channel)
• Iso-butane (C4H10): >1000 ppm (RED Channel)

Interface and Pinout Guide

• VCC: 5V DC Power Input
• GND: Common Ground Reference
• NO2 / OX: Analog Output for Oxidizing Gases channel (measures NO2)
• NH3: Analog Output for Ammonia channel
• CO / RED: Analog Output for Reducing Gases channel (measures CO, H2, C2H5OH, and hydrocarbons)

Key Features

• Triple-Sensing Element Array: Houses three independent MEMS sensor chips on a single substrate to differentiate between reducing, oxidizing, and nitrogen-based gas compounds.
• Compact MEMS Design: Micro-machined silicon diaphragm structure ensures rapid thermal response, low power draw, and a tiny physical footprint.
• Direct Analog Outputs: Outputs independent analog voltages for each sensing channel, making it easy to sample using standard microcontroller ADC pins.
• Broad Environmental Detection: Ideal for multi-gas tracking without needing multiple bulky individual gas sensor modules.

Common Applications

• Automotive Exhaust & Traffic Monitors: Detecting nitrogen dioxide and carbon monoxide levels along roadsides or inside vehicle cabins.
• Agricultural & Livestock Facilities: Monitoring ammonia concentrations in poultry farms, barns, and fertilizer storage sites.
• Industrial Safety Alarms: Sensing flammable gas leaks (methane, propane, hydrogen) and toxic carbon monoxide spikes.
• Smart Air Purifiers & IoT Nodes: Integrating comprehensive air quality index tracking into home automation and environmental logging systems.

Usage Tips

• Preheating Requirement: Metal-oxide (MOS) sensors require internal heating elements to reach operating temperatures. Allow at least 15–30 minutes of continuous preheating on initial power-up before taking precise calibration measurements.
• Resistance-Based Conversion: The raw outputs are variable resistances. To convert the analog voltage to gas concentration (ppm), calculate the ratio of the sensor's current resistance (Rs) against its baseline resistance in clean air (R0) using standard datasheet logarithmic curves.
• Cross-Sensitivity Management: The RED channel responds to multiple reducing gases (CO, H2, Ethanol). If precise identification of a single gas is needed, combine baseline calibration math with cross-sensitivity compensation in your firmware.

Datasheets:

MICS-6814 Air Quality Sensor Datasheet
Arduino Github Library for MICS-6814