In the production and life of modern society, people are often exposed to various gases and need to be detected and controlled, such as the detection and control of gas components in chemical production; detection and alarm of coal mine gas concentration; environmental pollution Situation monitoring; gas leakage: fire alarm; combustion detection and control, etc. The gas-sensitive resistance sensor is a sensor that converts the detected gas composition and concentration into electrical signals.
- 1. What is a gas sensitive Resistor
- 2. Working principle of gas-sensitive resistor
- 3. The characteristics of gas-sensitive resistors
1. What is a gas sensitive resistor
Gas sensitive resistor is a sensor that converts the composition and concentration of the detected gas into electrical signals. It is made by using some semiconductors to absorb a certain gas and then undergoing oxidation-reduction reactions. The main component is metal oxide. Its main varieties are: metal oxide gas sensitive resistors, composite oxide gas sensitive resistors, ceramic gas sensitive resistors and so on.
2. Working principle of gas-sensitive resistor
A gas-sensitive resistor is a semiconductor sensitive device, which uses the mechanism of gas adsorption to change the conductivity of the Semiconductor itself for detection. It has been found that certain oxide semiconductor materials such as SnO2, ZnO, Fe2O3, MgO, NiO, BaTiO3, etc. have gas-sensing effects.
3. The characteristics of gas-sensitive resistors
At present, there are two kinds of gas sensors made in China. One is the direct heating type, the heating wire and the measuring electrode are sintered in the metal oxide semiconductor core together; the other is the indirect heating type, this kind of gas sensor is based on a ceramic tube with a heating wire inside the tube, and there is a heating wire on the outside of the tube. The two measuring electrodes are made of metal oxide gas-sensitive material after high temperature sintering between the measuring electrodes.
Take the SnO2 gas sensor as an example. It is a collection of 0.1–10um crystals, which work as N-type semiconductors. Under normal circumstances, it is in a state of oxygen ion deficiency. When encountering combustible gas molecules with low dissociation energy and easy to lose electrons, the electrons migrate from the gas molecules to the semiconductor, and the carrier concentration of the semiconductor increases, so the conductivity increases. For p-type semiconductors, its crystal lattice is in a state of cation vacancy, and its conductivity decreases when it encounters flammable gases.