An Improved Humidity Sensor

Abstract

A common feature of all capacitance humidity sensors is their undesirable hysteresis effect due to the unequal adsorption and desorption of water vapor on the surfaces of their dielectric porous materials. To eliminate this error, an improved humidity sensor has been used composed of a commercial capacitive polymer sensor chip and an infrared (IR) radiation corrector emitting at a wavelength of 0.93 µm. The IR photons excite water molecule vibrations and destroy the bonds between water vapor and the material surface molecules, thus reducing residual hysteresis. Linearity is also improved, drift at high humidity is diminished, and response time is decreased.