Patent ID: 7176700

Claim:
A moisture sensor device comprising: a sensor portion having a capacitance that is varied in accordance with surrounding humidity; a signal processor for processing a detection signal of the sensor portion and outputting the signal corresponding to the humidity; a heating portion for heating the sensor portion; and a controller for controlling beating of the heating portion so that the capacitance of the sensor portion is substantially equal to a value under predetermined humidity at least during a self-diagnosis period; wherein the sensor portion comprises a substrate, a pair of detection electrodes disposed on the surface of the substrate so as to be spaced from each other and face each other, a detector that is provided on the substrate so as to cover the gap between the detection electrodes and whose relative permittivity is varied in accordance with moisture, and a reference capacitance portion that is provided on the same plane as the detection electrodes and has a pair of reference electrodes having substantially the same construction as the detection electrodes; wherein the signal processor is equipped with a switched capacitor type C-V converter for converting the capacitance difference between the capacitance value of the detector and the capacitance value of the reference capacitance portion to the corresponding voltage; wherein the heating portion comprises a heating element provided on the substrate; wherein the heating element comprises a resistor as a heater electrode that is supplied with current to generate heat: wherein the resistor is provided below the detection electrodes and the reference electrodes through an insulating layer; wherein the resistor has substantially the same width as facing portions of the detection electrodes and the reference electrodes, and are provided in connection with the facing portions.