A DIGITAL HYGROMETER USING A POLYIMIDE FILM RELATIVE-HUMIDITY SENSOR

A digital hygrometer using a relative humidity sensor is developed, Th e sensor consists of a polyimide film spin-coated onto an Si substrate , The sensor model for signal processing, which describes the sensor c apactiance in terms of relative humidity and temperature in closed for m, is derived first. The interface appropriate for the sensor model, b ased on a relaxation oscillator, is designed next, Finally, a prototyp e hygrometer built using a one-chip microprocessor and its performance are described to demonstrate the validity of the sensor model and int erface.