Five 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.
advantage
Semiconductor gas sensors can be effectively used for detecting many gases such as methane, ethane, propane, butane, alcohol, formaldehyde, carbon monoxide, carbon dioxide, ethylene, acetylene, vinyl chloride, styrene, acrylic acid, etc. Especially, this type of sensor is low-cost and suitable for the needs of civilian gas detection. The following semiconductor gas sensors are successful: methane (natural gas, biogas), alcohol, carbon monoxide (city gas), hydrogen sulfide, ammonia (including amines and hydrazine). High quality sensors can meet the needs of industrial testing.
shortcoming
Poor stability and significant environmental impact; Especially, the selectivity of each sensor is not limited to one, and the output parameters cannot be determined. Therefore, it is not suitable for places that require accurate measurement.
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.
advantage
Catalytic combustion gas sensors selectively detect combustible gases: anything that cannot be burned has no response from the sensor. Catalytic combustion gas sensors have accurate measurement, fast response, and long lifespan. The output of sensors is directly related to the explosion hazard of the environment and is a dominant type of sensor in the field of safety detection.
shortcoming
Within the range of flammable gases, there is no selectivity. Working in a dark environment poses a risk of ignition and explosion. Most organic vapors have a toxic effect on sensors.
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. Electrochemical gas sensors are divided into many subcategories
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.
