Detailed Working Principles of Carbon Monoxide (CO) Sensors

Carbon monoxide (CO) is a colorless, odorless "silent killer" commonly found in household heating, industrial production, and automobile exhaust. High concentrations can lead to poisoning or death. Timely and accurate detection is essential for life safety. CO sensors, as core tools, achieve precise monitoring through multiple technological principles. Nexisense, with over 40 years of experience in gas sensing technology, has developed a broad range of CO sensors, including electrochemical, semiconductor, and infrared optical types. This article examines these principles, detailing their mechanisms, technical characteristics, comparative analysis, and innovative applications, helping you fully understand CO sensors and guide practical selection. With this knowledge, you can better evaluate sensor suitability across scenarios and enhance safety protection.

Overview of Core Principles

CO sensors essentially capture the interaction between CO molecules and specific materials, converting it into measurable electrical or optical signals. Main principles include electrochemical, semiconductor, and infrared optical technologies, each designed for different requirements. Electrochemical sensors focus on low-concentration, high-precision detection; semiconductor sensors suit high-temperature, wide-range monitoring; infrared optical sensors emphasize long life and interference resistance. Nexisense provides optimized products for each principle, ensuring seamless application from laboratories to industrial sites.

When selecting a principle, environmental factors such as temperature, humidity, interfering gases, and cost should be considered. Electrochemical sensors perform efficiently at room temperature, semiconductor sensors withstand high temperatures, and infrared sensors are unaffected by oxygen. These differences originate from molecular-level reaction mechanisms, detailed below.

Electrochemical Working Principle

Electrochemical CO sensors simulate battery reactions, using CO oxidation-reduction on electrodes to generate a current signal. This principle offers high sensitivity, suitable for trace detection.

Basic reactions occur between the working electrode (WE) and counter electrode (CE):

The process begins with CO diffusion through a porous membrane into the electrolyte, reaching the working electrode surface where oxidation occurs and electrons generate a current. The current is proportional to CO concentration, amplified and output. The entire reaction occurs at room temperature, with low power consumption.

Technical specifications: detection range 0–1000 ppm, accuracy ±2% FS, response time<30 s, lifespan 2–3 years. Advantages: high selectivity and sensitivity to CO. Consider electrolyte consumption and humidity. Nexisense optimizes nano-electrode materials to enhance reaction efficiency and reduce cross-interference (e.g., hydrogen).

Common applications: home alarms trigger warnings if CO exceeds thresholds (e.g., 50 ppm), ensuring household safety.

Semiconductor Working Principle

Semiconductor CO sensors rely on conductivity changes in metal oxide materials, suitable for high-temperature or high-concentration environments.

Detection mechanism: CO reacts with oxygen ions adsorbed on the semiconductor surface, releasing electrons and increasing carrier density, raising conductivity. Common materials include SnO₂; in CO presence, resistance decreases proportionally to concentration.

Process: CO adsorbs on the heated semiconductor, reacts with oxygen, releases electrons, changes resistance, and produces output signals. Heating (200–400°C) ensures reaction activity.

Technical characteristics: detection range 0–5000 ppm, low cost, high-temperature suitability, accuracy ±5% FS, response<60 s, lifespan 3–5 years. Limitations: humidity sensitivity, moderate selectivity. Nexisense improves humidity resistance through doped materials.

Typical applications: industrial furnace monitoring in high-temperature gas environments, avoiding thermal failures of electrochemical sensors.

Infrared Optical Working Principle

Infrared optical CO sensors use non-contact optical methods, leveraging CO’s absorption of specific infrared light for interference-free detection.

Principle: according to Lambert-Beer law, CO absorbs infrared light at 4.6 μm, absorption intensity proportional to concentration. Concentration is calculated by measuring light attenuation.

Process: infrared light passes through the sample chamber, CO absorbs part of the light, detector measures remaining intensity, and signal processing outputs concentration. The system is sealed, avoiding chemical consumption.

Technical features: detection range 0–10000 ppm, accuracy ±1% FS, response<10 s, lifespan 5–10 years. Excellent interference resistance, unaffected by oxygen or humidity, but higher cost. Nexisense’s optical cavity and light source optimize SNR and reduce power consumption.

Applications: environmental monitoring stations for continuous high-precision atmospheric data.

Comparative Analysis of the Three Principles

Electrochemical: high precision, low power, shorter lifespan. Semiconductor: low cost, high-temperature tolerance, moderate selectivity. Infrared: stable, long life, strong interference resistance, suited for premium applications.

Detection ranges: Electrochemical 0–1000 ppm, Semiconductor 0–5000 ppm, Infrared 0–10000 ppm. Accuracy: Infrared ±1% FS (best), Electrochemical ±2% FS, Semiconductor ±5% FS. Response: Infrared<10 s fastest. Lifespan: Infrared 5–10 years. Cost: Semiconductor < Electrochemical < Infrared. Interference resistance: Infrared best.

Recommendation: home use – electrochemical; industrial high-temp – semiconductor; precise monitoring – infrared.

Nexisense Innovations and Application Expansion

Nexisense optimizes CO sensors: electrochemical types with nano-electrodes and temperature compensation algorithms improve sensitivity, accuracy, zero-drift <±1 ppm/month. Infrared sensors with optimized optical cavity and smart algorithms reduce false alarms<0.1%.

Applications: smart homes (ventilation control), automobiles (cabin air monitoring), coal mines (real-time explosion warning). Proven to reduce accidents and enhance safety.

FAQ

1. Main CO sensor principles? Electrochemical, semiconductor, and infrared optical.

2. How does electrochemical CO sensor generate signal? CO oxidation-reduction reaction generates current proportional to concentration.

3. Why heat semiconductor sensor? Heating (200–400°C) activates surface reaction, increasing sensitivity.

4. Infrared absorption wavelength? 4.6 μm.

5. Precision comparison? Infrared ±1% FS, Electrochemical ±2% FS, Semiconductor ±5% FS.

6. Response time? Time from gas exposure to stable output (e.g., Electrochemical<30 s).

7. Factors affecting lifespan? Humidity, temperature, exposure frequency, material quality.

8. Nexisense innovations? Nano-electrodes improve sensitivity, optical cavity enhances SNR.

9. How to choose sensor type? Home – electrochemical, Industrial high-temp – semiconductor, Precision – infrared.

10. Role in homes? Detect leaks, trigger alarms, protect families.

Conclusion

CO sensors utilize diverse principles: electrochemical current signals, semiconductor resistance changes, and infrared light absorption, each with advantages. Nexisense provides reliable products supporting basic detection to intelligent integration. Selecting the appropriate sensor ensures safety and life protection. Proper application reduces risks and promotes a safer, greener lifestyle.