Carbon Dioxide (CO2) Sensor Working Principles

In today's environmentally conscious and health-focused world, monitoring carbon dioxide (CO2) levels has become essential in industrial production, agricultural cultivation, smart homes, and environmental assessment. Excessive CO2 can reduce comfort and contribute to the greenhouse effect. Nexisense, with over 40 years of experience in gas sensing technology, develops reliable CO2 sensor solutions to enable precise measurement and intelligent control. This article details the core principles of NDIR, electrochemical, and semiconductor technologies, analyzing their characteristics, advantages, and multi-scenario applications. Understanding these principles helps select the appropriate sensor for efficient environmental management.

Overview of CO2 Sensors

A CO2 sensor measures the concentration of CO2 in the air, typically outputting data in ppm (parts per million). Its operation relies on the unique physical and chemical properties of CO2, such as infrared absorption at specific wavelengths or chemical reactions with materials. Main technologies include NDIR (non-dispersive infrared), electrochemical, and semiconductor, each with distinct advantages: NDIR offers high accuracy and stability, electrochemical emphasizes fast response and portability, and semiconductor features small size and low power consumption.

Nexisense products include TX640-J812 low-power CO2 sensor, TX640-J811 CO2 sensor, and TXZ19D infrared CO2 gas sensor. These sensors are designed for environmental adaptability, covering indoor trace monitoring to high-concentration industrial detection. Understanding principles aids proper selection and reduces application errors.

NDIR (Non-Dispersive Infrared) Principle

NDIR is the most mature CO2 sensing technology, based on CO2 absorption of infrared light. CO2 strongly absorbs IR light around 4.26 μm. When the beam passes through CO2-containing gas, part of the light is absorbed, and the remaining intensity decreases. Concentration is calculated from this change.

Workflow: an IR source emits broadband light, a filter selects a specific wavelength, the light passes through the gas chamber, and a detector measures transmitted light. A reference channel (no CO2 absorption) compensates for environmental interference such as temperature or dust. Signal processing applies Beer-Lambert law to output concentration.

Advantages: strong anti-interference, unaffected by oxygen or humidity, accuracy ±50 ppm, lifespan up to 10 years. Suitable for labs or industrial emissions. Light source aging is mitigated by optimized optics and self-calibration algorithms.

Electrochemical Principle

Electrochemical CO2 sensors generate electrical signals through chemical reactions of CO2 with an electrolyte, similar to a micro battery. CO2 diffuses into the sensor and undergoes a reduction reaction at the working electrode, producing current proportional to concentration.

Typical reaction in acidic electrolyte: CO2 dissolves to form carbonic acid, reacts with electrode catalyst, releasing electrons. Current in nA range is amplified to voltage or current output. Gas diffuses through membrane to electrolyte, reaction generates current, circuit outputs signal.

Features: fast response (<30 s), low cost, portable, ideal for handheld devices. Lifespan 2–3 years, humidity sensitive, selectivity may need filtering. Nexisense optimizes electrolyte composition for anti-poisoning and reliable performance in humid environments.

Semiconductor Principle

Semiconductor CO2 sensors use metal oxide materials whose resistance changes when CO2 adsorbs on the heated surface (SnO2 or ZnO), altering carrier concentration and decreasing resistivity.

Workflow: sensor heats to 200–400°C, CO2 adsorption triggers surface reactions, releasing or capturing electrons, resistance change detected via Wheatstone bridge circuit.

Advantages: small size, low power (milliwatt-level), suitable for consumer smart home devices. Wide detection range, slightly lower accuracy (±100 ppm), sensitive to interfering gases. Nexisense improves selectivity and stability through doping and coatings.

Technology Comparison

Complementary principles: NDIR – highest accuracy, best anti-interference, larger size; Electrochemical – fast response, portable, limited lifespan; Semiconductor – compact, low power, selectivity needs optimization. Nexisense recommends: NDIR for precision, Electrochemical for portability, Semiconductor for embedded solutions.

NDIR dominates industrial applications, electrochemical is popular in mobile devices, semiconductor in consumer electronics. Differences arise from molecular interactions; understanding avoids misuse.

Nexisense Technological Advantages

Nexisense leverages 40 years of experience. NDIR sensors achieve ±50 ppm accuracy and stability, with laser calibration and multi-optical paths reducing drift. TX750-J161 infrared CO2 sensor operates from -20°C to 60°C.

Full-scenario adaptability: TXZ19D for greenhouses to TX640-J812 for smart homes, covering industrial emissions and building ventilation. Customizable sensitivity, size, and output (4–20 mA or RS485) enable seamless integration. Temperature compensation algorithms ensure accurate measurement under changing conditions.

Typical Applications

Agriculture: NDIR sensors maintain optimal CO2 in greenhouses, boosting plant growth; below 800 ppm triggers supplementation, increasing yield 10–20%.

Smart homes: Semiconductor sensors integrated into HVAC systems trigger ventilation above 1000 ppm CO2, improving air quality and reducing discomfort.

Industrial emissions: Electrochemical sensors provide portable inspection and environmental compliance monitoring. Nexisense sensors support energy saving and emission reduction projects.

FAQ

1. What are the main CO2 sensor principles? NDIR, electrochemical, and semiconductor.

2. How does NDIR work? Measures light absorption by CO2, strong anti-interference.

3. Advantages of electrochemical sensors? Fast response, low cost, 2–3 years lifespan.

4. Where are semiconductor sensors suitable? Small, low-power devices, smart home products.

5. Typical accuracy? NDIR ±50 ppm, Electrochemical ±100 ppm, Semiconductor slightly lower.

6. Factors affecting lifespan? Temperature, humidity, exposure, material quality.

7. Can Nexisense sensors be customized? Yes, sensitivity, size, and output interface adjustable.

8. CO2 sensor use in agriculture? Monitors and controls levels, enhancing growth and yield.

9. How to choose sensor type? Precision – NDIR, portable – Electrochemical, low-cost – Semiconductor.

10. Output methods? Voltage, current (4–20 mA), or digital RS485 for easy integration.

Conclusion

CO2 sensors use diverse principles: optical absorption (NDIR), electrochemical current, and semiconductor resistance change. Nexisense provides a full range of products for industrial and home applications. In the era of carbon neutrality, these technologies are essential for monitoring and energy management. Proper selection improves efficiency and safeguards health.