Patent ID: 7114391

Claim:
An apparatus for detecting the level of a liquid, comprising: a pair of first electrodes at least partly immersed in the liquid; a pair of second electrodes arranged at a different height to that of the first electrodes and at least partly immersed in the liquid; a pair of electrode leads having respective ends connected with the first electrodes and sandwiching therebetween the second electrodes; a grounding unit that changes, between a current-carrying state and an open state, a second electrode current bypass from the second electrodes to a ground line; a first electrode capacitance measurement unit that measures a first electrode capacitance between the first electrodes, with the second electrode current bypass set in the current-carrying state to establish a connection from the second electrodes to the ground line; and a level determination unit that determines the liquid level based on the first electrode capacitance between the first electrodes and a second electrode capacitance between the second electrodes.