Patent ID: 7134332

Claim:
A liquid-amount detecting apparatus for detecting the amount of a liquid contained in at least one container, the liquid detecting apparatus comprising: a liquid detecting circuit comprising an electrode unit formed by a pair of electrodes that is disposed at a location corresponding to a level of liquid in the container, the pair of electrodes being electrically connected to each other when the pair of electrodes is in contact with the liquid; a source impedance; and a single alternating-current signal source; wherein the liquid detecting circuit causes an alternating-current signal not containing a direct-current component to be selectively input to each electrode unit through the source impedance, and outputs a binary signal representing the presence or absence of an electrical connection between the pair of electrodes; and a determining unit for determining the presence or absence of the liquid at the electrode unit based on the binary signal output from the liquid detecting circuit, and further wherein a frequency of the alternating-current signal is at least 1 kHz.