A digital hygrometer

A digital hygrometer using a polyimide capacitive humidity sensor is developed. The capacitance change of the sensor due to adsorption of water vapor in the atmosphere is detected by a switched-capacitor digital capacitance bridge controlled by a one-chip microcomputer and is displayed as relative humidity with 0.1% resolution. The accuracy of the hygrometer calibrated by a two-point method is solely determined by the temperature dependence and the long-term drift of the dielectric sensitivity of the sensor and is estimated to be 2%.<
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