Types of Sensors Used in Gas Detectors and Their Corresponding Advantages and Disadvantages
Gas detector is an instrument tool for detecting gas leakage concentration, mainly referring to portable/handheld gas detectors. Mainly using gas sensors to detect the types of gases present in the environment, gas sensors are sensors used to detect the composition and content of gases. It is generally believed that the definition of gas sensors is based on the classification of detection targets, which means that any sensor used to detect gas composition and concentration is called a gas sensor, regardless of whether it uses physical or chemical methods. For example, sensors that detect gas flow are not considered gas sensors, but thermal conductivity gas analyzers are important gas sensors, although they sometimes use generally consistent detection principles.
Types, advantages, and disadvantages of sensors for gas detection instruments
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 unique, and the output parameters cannot be determined. Therefore, it is not suitable for places that require accurate measurement.
The combustion type sensor is a high-temperature resistant catalyst layer prepared 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.
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.
