Humidity Sensor Using Al₂O₃, TiO₂ and SnO₂ Prepared by Sol-Gel Method

Abstract

Ultra-fine paticles of Al₂O₃, TiO₂ and SnO₂ prepared by the sol-gel method for humidity sensing materials with an optimal porous structuture, a superior humidity sensing characteristics have been acquired in a humidity range of 10 to 95% RH and at an operation temperature of -20 to 100°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°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.