Study of a silicon parallel plate capacitor as a dew point sensor

In this work we study a silicon parallel plate capacitor as a dew point sensor. Accumulation of water between the parallel plates below dew point temperature leads to an increase in capacitance. The expected 80-fold increase in capacitance (ratio of relative permittivity of water to air) holds true at high frequencies while at low frequencies an increase up to four orders of magnitude has been measured. We report that the condensed water models more as a conductor than as a dielectric at low frequencies, which, along with the native oxide of silicon, explains the unexpected increase in capacitance.