subject: Works And Structural Characteristics Of The Semiconductor Gas Sensor [print this page] The main semiconductor type gas sensor, contact combustion, chemical reaction formula, the light interference, heat conduction type, the infrared absorption decentralized. This semiconductor gas sensor applied more widely.
The semiconductor gas sensor is constituted by the gas-sensitive part of the heating wire, and the explosion-proof net, which is Pt, Pd, etc. is added to the metal oxide in the gas-sensitive part of the SnO2, Fe2O2, ZnO2 etc. sensitizer sensor. The selectivity of the sensor is controlled by the number of add sensitizer For example, for the sensor of ZnO2 series, if the addition of Pt, then the sensor of propane and isobutane, higher sensitivity; if added Pd, is more sensitive to CO and H2 .
Gas sensor ceramic tube frame, the sensitive membrane covered with a layer of material, the use of the film both ends of the gold-plated pin measurements. The sensitive material of the film most commonly used are the metal oxides, polymer materials and colloidal sensitive film. The two key parts of it is the heating resistor and the gas-sensitive film. Gold electrode connecting both ends of the gas-sensitive material so that it is equivalent to a resistance change of the gas concentration to be measured with the external resistor. Since the metal oxide has a high thermal stability, but such a sensor only on the semiconductor surface layer produce a reversible oxidation reduction reaction, the same chemical structure of the internal semiconductor, therefore, long-term use also obtained a higher stability. The principle outlined below: Once heated, the metal oxide, the oxygen in the air will be crystallized from the metal oxide semiconductor of the donor level of the particles in the claimed electronic adsorbed negative electron on the crystal surface, so that the surface potential increased, thus impeding the conduction electron movement of the gas sensor in the air for a constant resistance value. Oxidation reaction occurs when the oxygen adsorbed by the reducing gas with the semiconductor surface, away from the suction effect of the gas molecules to the surface potential level of change and, therefore, the resistance value of the sensor to change. For reducing gas, the resistance value decreases; for the oxidizing gas, the resistance value increases. Thus, according to the change of the resistance value will be able to detect the concentration of gas.
