Description of various sensor types for gas detectors
1. Semiconductor gas sensor
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. 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.
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Several semiconductor gas sensors have been 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. However, they also have their own shortcomings. These drawbacks include: poor stability and significant environmental impact; Especially, the selectivity of each sensor is not unique, and the output parameters cannot be determined. Therefore, it is not suitable for places that require accurate measurement.
At present, the main suppliers of this type of sensor are in Japan, followed by China, and recently South Korea has also joined. Other countries such as the United States have considerable work in this area, but it has not yet been integrated into the mainstream. China has invested as much manpower and time in this field as Japan, but due to years of national policy guidance and social information blockage, the performance and quality of semiconductor gas sensors popular in the market in China are far inferior to Japanese products.
2. Catalytic combustion gas sensor
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.
Catalytic combustion gas sensors selectively detect flammable gases: anything that can burn can be detected; Anything that cannot burn has no response from the sensor. Of course, anything that can burn can be detected with many exceptions. However, overall, the above selectivity is valid.
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. Its disadvantage is that it has no selectivity within the flammable gas range. Working in a dark environment poses a risk of ignition and explosion. Most organic vapors have a toxic effect on sensors.
