Semiconductor gas sensor working principle and characteristics

There are semiconductor type gas sensor , a catalytic combustion method , chemical reaction , optical interference , thermal conductivity , infrared absorption , etc. decentralized . Which is among the semiconductor gas sensor applications more widely. The semiconductor gas sensor part from the gas , the heating wire and the protective screen and the like , it is in the gas part of the SnO2, Fe2O2, ZnO2 adding metal oxides such as Pt, Pd and other sensors sensitizer . Selectivity of the sensor by the number of sensitizer added is controlled , for example, for ZnO2 series Engine Temperature Sensor , if adding Pt, the sensor for propane and isobutane with high sensitivity ; if added Pd, is relatively sensitive to CO and H2 . Gas sensors with ceramic tube frame , covered with a layer of sensitive material of the film , the use of gold-plated pin across the membrane is measured . Sensitive material of the film most commonly used metal oxides , polymers and colloidal materials sensitive film. Its two key part of the heating resistor and the gas -sensitive film . Sensitive material gold electrode connected at both ends to make it equivalent to a resistance with external test gas concentration changes resistance . Since the metal oxide has a high thermal stability , and Crank Shaft Position Sensor is only the surface layer of the semiconductor produce a reversible redox reaction , the same chemical structure inside the semiconductor , so long-term use high stability can be obtained . Introduction Principles as follows : Once the heated metal oxide , the oxygen in the air will be from a metal oxide semiconductor crystal particles away electron donor level in , adsorbed on the surface in the crystallization negative electron , the surface potential increases , thus preventing conduction electron mobile , so  Crankcase Position Sensor  in the air is constant resistance value. Then the reducing gas and oxygen adsorbed semiconductor surface oxidation of the gas molecules to the surface of suction effect from the low electric potential changes, therefore , the resistance value of the sensor to change. For the reducing gas , the resistance value decreases ; the oxidizing gas , the resistance value increases . Thus, the resistance value changes according to the gas concentration can be detected .