US Patent 8667840 Water level sensing apparatus

There is provided a water level sensing apparatus including: a body disposed to be exposed within a liquid tank and having an accommodating space therein; and a capacitance detecting unit accommodated in the accommodating space of the body, wherein the capacitance detecting unit compares an upper side capacitance value and a lower side capacitance value and turns on or off an output signal. Because a changeable reference that the capacitance values of a reference surface and a detected surface of the body are simultaneously changed is used, even if the body comes in contact with moisture or debris, the reference surface and the detected surface are equally affected by the moisture or debris, thus reducing the occurrence of malfunction.