US Patent 7340952 Capacitive humidity sensor

A capacitive humidity sensor includes a printed circuit board having an insulating substrate on which a circuit section is formed, a pair of electrodes formed on a surface of the insulating substrate to be opposite from each other with a space, and a humidity sensitive layer formed on the insulating substrate to cover the electrodes and the surface of the insulating substrate between the pair of electrodes. The relative permittivity of the humidity sensitive layer changes in response to humidity, and the circuit section performs a signal processing of a capacitance change between the electrodes. Furthermore, the electrodes and the circuit section are electrically connected through a wiring section formed in the insulating substrate.