HUMIDITY SENSOR USING AL2O3, TIO2 AND SNO2 PREPARED BY SOL-GEL METHOD

Ultra-fine paticles of Al2O3, TiO2 and SnO2 prepared by the sol-gel method for humidity sensing materials with an optimal porous structure, a superior humidity sensing characteristics have been acquired in a humidity range of 10 to 95% RH and an operation temperature of -20 to 100-degrees-C. The sensing mechanism of this humidity sensor utilizes the variation in proton conductivity in absorbed water. This mechanism has proved to be hard to use at temperatures above 100-degrees-C. Heat cleaning by a ceramic heater enables us to improve humidity sensors of high reliability and high precision. They are exellent in withstanding various corrosive environments over a long period.