A digital hygrometer using a capacitance-to-frequency converter

摘要

A digital hygrometer using a relative humidity sensor isdeveloped. The sensor consists of a polyimide film spin-coated onto a Sisubstrate. The sensor model for signal processing is first derived whichdescribes the sensor capacitance in terms of relative humidity andtemperature in closed form. The interface appropriate for the sensormodel is next designed based on a relaxation oscillator. A prototypehygrometer built using a one-chip microcomputer for signal processingand its performance are finally described to demonstrate the validity ofthe sensor model and interface