Patent ID: 7049969

Claim:
A liquid detection apparatus comprising: a liquid detection sensor to be attached to an object to be monitored, said liquid detection sensor comprising: a resonant circuit including: a coil having at least two winding faces arranged to have a three-dimensional shape; and a capacitor having a pair of electrodes and a dielectric interposed between said pair of electrodes; and a noncontact tag including a covering material covering said resonant circuit, said covering material having a through-hole for allowing liquid to infiltrate into said dielectric of said resonant circuit; a detection radio wave emitting unit operable to emit a detection radio wave to said liquid detection sensor by sweeping a frequency of the detection radio wave emitted therefrom; a radio wave receiving unit operable to receive a radio wave returned from said liquid detection sensor when the detection radio wave is emitted by said detection radio wave emitting unit; a frequency specifying unit operable to specify a frequency corresponding to a lowest level of the radio wave received by said radio wave receiving unit; a frequency fluctuation detecting unit operable to detect a fluctuation in the frequency specified by said frequency specifying unit; and a decision unit operable to determine wetness or dryness of the object to be monitored based on an amount of the fluctuation in the frequency specified by said frequency specifying unit.