Five major types of gas detectors
1, Semiconductor type
It is manufactured using the principle that the conductivity of some metal oxide semiconductor materials changes with the composition of the ambient gas at a certain temperature. For example, an alcohol sensor is prepared based on the principle that when tin dioxide encounters alcohol gas at high temperatures, its resistance will sharply decrease.
2, Combustion type
This type of sensor is prepared with a high-temperature resistant catalyst layer on the surface of a platinum resistor. At a certain temperature, combustible gases catalyze combustion on its surface. Combustion is a function of the concentration of combustible gases as the temperature of the platinum resistor increases and the resistance changes.
3, Thermal conductivity pool type
Each gas has its own specific thermal conductivity, and when there is a significant difference in thermal conductivity between two or more gases, a thermal conductivity element can be used to distinguish the content of one component. This type of sensor has been widely used for detecting hydrogen, carbon dioxide, and high concentration methane.
This gas sensor has a narrow application range and many limiting factors.
4, Electrochemical formula
A significant portion of its flammable, toxic, and harmful gases have electrochemical activity and can be electrochemically oxidized or reduced. By utilizing these reactions, gas composition can be distinguished and gas concentration can be detected.
5, Infrared radiation
Most gases have characteristic absorption peaks in the mid infrared region. By detecting the absorption situation of the characteristic absorption peak position, the concentration of a certain gas can be determined.
This type of sensor used to be a large analytical instrument, but in recent years, with the development of the sensor industry based on MEMS technology, the volume of this sensor has decreased from a giant of 10 liters and 45 kilograms to around 2 milliliters (thumb size). The use of infrared detectors that do not require modulation of light sources makes the instrument completely free of mechanical moving parts and maintenance free. Infrared gas sensors can effectively distinguish the types of gases and accurately measure gas concentrations.
