Air Sensor Circuit Diagram

Published:2011/5/10 2:28:00 Author:Felicity | Keyword: Air Sensor Circuit Diagram, | From:SeekIC

　The resistance of some semiconductor decreases dramatically as the temperature increases in the atmosphere of some certain gas. And the performance of some material changes greatly while the gas concentration reaches a certain point. Thus this kind of semiconductor material including ferric oxide, tin oxide and zinc oxide could be made into air sensor. They will react under the atmosphere of methane, butane, ethanol or benzene. Figure 1 shows the relation curve of the resistance of typical sensor R and the gas concentration P. The air sensor ,type 8222 418 20031, is made according to this theory. It is consisted of a millimeter-size ceramic plate heating lamp and a electrode opposite to it. The work temperature is 300℃. It can work under both AC and DC condition. Figure 2 shows a simple air warning circuit. While the resistance of the 1kΩcontinuous potentiometer exceed a certain point, the thyristor will be turned on,and then the relay actuate to send a signal or make the actuator off. It is not until the stop button S is pressed that the relay is off again



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