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Classification and Working Principle of Gas Monitoring Sensors

Gas monitoring sensors play a crucial role in detecting and measuring the presence of various gases in different environments, from industrial settings to home safety systems. These sensors come in several types, each based on different physical or chemical principles. Understanding their classification and working mechanisms helps in selecting the right sensor for specific applications. Semiconductor gas sensors are among the most common. They can be further divided into resistive and non-resistive types. Resistive sensors work by detecting changes in the resistance of a semiconductor material when it comes into contact with a target gas. Non-resistive sensors, on the other hand, rely on changes in other properties such as capacitance or current due to gas adsorption and reaction. Contact-combustion sensors operate based on the heat generated when a flammable gas is burned on a catalytic surface. This heat causes a temperature rise, which in turn affects the conductivity of a metal electrode. These sensors are less affected by humidity compared to some other types. Capacitive gas sensors detect gas by measuring changes in the dielectric constant of a sensitive material. As the gas interacts with the material, the capacitance changes, allowing the sensor to determine the gas concentration. Electrochemical sensors are widely used for their high accuracy and stability. They function by using a chemical potential difference between two electrodes—one active and one reference. These sensors can operate through either potentiostatic electrolysis or galvanic cell methods. They may use liquid or solid electrolytes, with liquid ones typically categorized into potential and current types. In addition to these, there are other advanced types like infrared absorption sensors, quartz oscillation sensors, optical fiber sensors, thermal conductivity sensors, surface acoustic wave sensors, and gas chromatography systems. Each of these has unique advantages depending on the application environment and required sensitivity. Choosing the appropriate gas monitoring sensor depends on factors such as the type of gas being detected, environmental conditions, required accuracy, and cost. Proper selection ensures reliable performance and long-term stability in gas detection systems.