MG811 electrolyte carbon dioxide CO2 air quality sensor detector sensor

Description

The MG811 Electrolyte CO2 Sensor is a solid-electrolyte electrochemical gas sensor designed for detecting carbon dioxide concentration in air quality control systems, fermentation processes, and greenhouse environments. Unlike semiconductor MOX sensors like the MQ-135 that respond to a broad range of gases, the MG811 offers good sensitivity and selectivity to CO2, making it a more targeted choice for carbon dioxide monitoring applications.

At the heart of the sensor is a solid electrolyte battery principle. When the sensor is heated to its operating temperature and exposed to CO2, an electrode reaction occurs between the sensitive electrode and the reference electrode, generating an electromotive force (EMF). The output signal voltage has a logarithmic inverse relationship with CO2 concentration — as CO2 levels rise, the output voltage decreases. This allows the sensor to detect CO2 across a range of 0 to 10,000 ppm, with a zero-point EMF of 300–500 mV in 400 ppm CO2 and an output signal change (ΔEMF) of at least 25 mV between 400 ppm and 1000 ppm.

The sensor requires a heating voltage of 6.0V ± 0.1V (AC or DC) to reach its operating temperature, with a heating current of approximately 140–200 mA and power consumption around 850–1200 mW depending on the variant. This significant heater current means the module cannot be powered from a USB port alone — an external power supply (typically 7–12V) is required for the microcontroller board when using this sensor. The module includes an onboard conditioning circuit that amplifies the sensor’s high-impedance output signal, and a potentiometer for setting a digital threshold that triggers an onboard LED and digital output when CO2 levels exceed the set point.

Important Note: The MG811 is an electrochemical sensor that requires careful calibration before meaningful measurements can be made. DFRobot’s official guidance recommends powering the sensor in clean air for approximately 48 hours to stabilize, then measuring the output voltage and entering that value into the calibration code (dividing the measured voltage by the amplifier gain of 8.5). The sensor also needs calibration at 400 ppm (ambient) and 1000 ppm reference points for accurate ppm readings. The sensor’s high-impedance output (requiring amplifier impedance in the 100–1000 GΩ range) and logarithmic response mean that precise absolute CO2 measurement is challenging — the sensor is better suited for trend monitoring and threshold-based alarm applications than for laboratory-grade CO2 measurement. The sensor is not waterproof and should be kept dry. Operating temperature range is -20°C to +50°C.

Whether you are building a greenhouse CO2 enrichment controller, an indoor air quality monitor, or a fermentation process alarm, the MG811 sensor provides a targeted electrochemical solution for carbon dioxide detection with the documentation and community support of a widely used DFRobot-compatible module.

Features

• Solid-electrolyte electrochemical CO2 sensor — Good sensitivity and selectivity to carbon dioxide

• 0–10,000 ppm detection range — Suitable for ambient to enriched CO2 environments

• Logarithmic voltage output — Output voltage decreases as CO2 concentration increases

• 6.0V heater with onboard conditioning circuit — Maintains optimal sensor temperature and amplifies the high-impedance signal

• Adjustable digital threshold — Potentiometer sets alarm trigger point with LED indication

• Analog and digital outputs — Analog for trend monitoring, digital for threshold alarms

• Low humidity and temperature dependency — More stable than many semiconductor gas sensors

• Wide application range — Greenhouse CO2 control, fermentation monitoring, indoor air quality

• DFRobot-compatible module — Extensive documentation, sample code, and community support

• Long lifespan — Solid electrolyte construction for stable long-term operation

Technical Specifications