For different industry, different gas sensor or gas detector are used, like H2S gas detector ,ch4 gas detector or PID voc gas detector, they use different gas sensors.
The core of a gas detector lies in its sensor technology. Different types of sensors are suitable for different gases, different scenarios, and different accuracy requirements. Below is a comprehensive analysis of mainstream gas sensor types, allowing you to choose based on your target gas and detection needs (accuracy, response speed, lifespan, cost).
Classification by Detection Principle:
1. Semiconductor Sensors: For combustible gases (such as CH₄), VOCs, and CO. The principle is that the gas adsorbs onto the surface of a metal oxide, causing a change in resistance. Low cost, long lifespan, sensitive to combustible and VOC gases. Poor stability, easily affected by temperature and humidity, generally low accuracy, poor selectivity, and zero-point drift. Used in household gas alarms and low-end industrial safety warnings.
2.Catalytic Combustion Sensors: For combustible gases (methane, propane, etc.). The principle is that the gas burns on the surface of a catalytic bead, causing a change in the bridge resistance. Mature technology, good linear response to combustible gases, and long lifespan. Only suitable for combustible gases, oxygen-required environments, catalysts are easily poisoned (sulfides, silicides), and there is a risk of ignition.
3.Electrochemical Sensors, These sensors are used for monitoring flammable gases in petroleum, chemical, and mining environments to prevent explosions. They target toxic gases (CO, H₂S, SO₂, O₃, etc.) and oxygen (O₂). The gases undergo redox reactions in the electrolyte, generating a current proportional to the concentration. They offer high sensitivity, good selectivity, low power consumption, but have a limited lifespan (typically 1-2 years). They are affected by temperature and humidity, susceptible to cross-interference, and require periodic calibration. They are commonly used in portable personal protective equipment and for targeted monitoring of toxic gases in industrial applications.
4. Infrared Sensors: These sensors target infrared-active gases (CO₂, CH₄, propane, refrigerants, etc.) | Based on the Lambert-Beer Law, they measure the absorption of specific infrared wavelengths by the gas. They offer extremely long lifespan, high stability, good selectivity, are unaffected by oxygen, and are intrinsically safe. They are more expensive and are primarily used for carbon dioxide monitoring, greenhouse gas analysis, high-precision monitoring of flammable gases, and refrigerant leak detection.
5.Infrared Sensors: These sensors target infrared-reactive gases (CO₂, CH₄, propane, refrigerants, etc.). Based on the Lambert-Beer Law, they measure the absorption of specific infrared wavelengths by the gas. They offer extremely long lifespan, high stability, good selectivity, are unaffected by oxygen, and are intrinsically safe. They are more expensive and are commonly used for carbon dioxide monitoring, greenhouse gas analysis, high-precision monitoring of flammable gases, and refrigerant leak detection.
6. Photoionization sensor: Targeting volatile organic compounds and some toxic gases, it uses an ultraviolet lamp to ionize gas molecules and measures the resulting ion current. It has extremely high sensitivity to VOCs (ppb level), fast response, and non-destructive measurement. However, it cannot distinguish specific compounds (total VOCs), is insensitive to certain gases (such as CH₄), and has a limited UV lamp lifespan. Applications include industrial hygiene surveys, leak detection, environmental emergency monitoring, and contaminated site investigations.
7. Ultraviolet sensor: Targeting the absorption of specific wavelengths of ultraviolet light by gases such as ozone, chlorine, and mercury vapor (Lambert-Beer Law). It has a long lifespan, extremely high accuracy, good stability, and virtually no interference. However, it is expensive and highly specific (one sensor typically measures only one gas). It is widely used for online ozone monitoring and concentration analysis, industrial chlorine monitoring, and flue gas emission monitoring.
8. Laser sensor: Targeting specific gases (such as CH₄, HCl, NH₃), it uses a tunable laser diode absorption spectrum to measure specific absorption lines. 7. **Ultrasonic Sensor:** Extremely high sensitivity (ppb level), extremely fast response, extremely high selectivity, and capable of long-distance telemetry (open optical path). Very expensive and complex system. Primarily used for remote sensing of natural gas pipeline leaks, regional safety monitoring, and high-precision analysis.
9. Ultrasonic Sensor: Principle: Early leak warning is achieved by detecting ultrasonic signals generated by gas leaks. Features: - Non-contact, capable of long-distance detection. Suitable for monitoring leaks in high-pressure pipelines and storage tanks.
10. Thermal Conductivity Sensor: Principle: Detects concentration using differences in gas thermal conductivity, commonly used for hydrogen or high-concentration gases. Features: Suitable for high-concentration detection, no oxygen required. Lower accuracy, easily affected by ambient airflow.