A digital hygrometer

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