Definition of gas sensor
"A gas sensor is a converter that transforms the volume fraction of a gas into a corresponding electrical signal. The probe conditions the gas sample through the gas sensor, typically including filtering out impurities and interfering gases, drying or cooling, and the instrument display section." -> Baidu Encyclopedia
According to the definition in 3.3.1 of GB/T7665-2005 "General Terminology of Sensors", a gas sensor (gastransducer/sensor) is a sensor that can sense gas (components, partial pressure) and convert it into a usable output signal.
Generally, a gas sensor is a device that detects gas within a certain range using a gas-sensitive element and converts the output into an electrical signal that can be recognized and processed by a computer or microcontroller (MCU), thereby realizing the detection of gas composition and concentration.
Classification of gas sensors
Gas sensors can be classified into the following types according to their technology:
Electrochemical gas sensors utilize the electrochemical activity of the gas being detected, reducing or oxidizing it electrochemically to determine its concentration and composition. Common types of electrochemical sensors include galvanic cell type and constant potential electrolytic cell type. Currently, electrochemical sensors are the most mature and common sensors for detecting toxic and harmful gases.
Semiconductor gas sensors are made by utilizing the changes in the structure of the sensing element caused by the redox reaction of gas on the semiconductor surface. Semiconductor gas sensors consist of a detection element made of metal semiconductor oxide or metal oxide material. When interacting with gas, surface adsorption and reactions occur, causing changes in conductivity, current-voltage characteristics, or surface potential, characterized by carrier movement, to measure gas concentration.
Catalytic combustion gas sensors utilize the thermal effect of catalytic combustion. A measuring bridge is formed by paired detection and compensation elements. Under certain temperature conditions, combustible gas undergoes flameless combustion on the surface of the detection element carrier under the action of a catalyst. This increases the carrier temperature, consequently increasing the resistance of the platinum wire inside, thus unbalancing the bridge and outputting an electrical signal proportional to the combustible gas concentration. By measuring the change in the platinum wire's resistance, the concentration of the combustible gas can be determined. Primarily used for the detection of combustible gases, these sensors offer good linearity of the output signal, reliable exponential function, low cost, and no cross-contamination with other non-combustible gases.
Infrared gas sensor - a gas sensing device that identifies gas components and determines their concentration based on the selective absorption characteristics of different gas molecules in the near-infrared spectrum and the relationship between gas concentration and absorption intensity.
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