Patent ID: 7131328

Claim:
A liquid holding tank for a printer comprising: at least one container which contains a liquid that is used in a printer; and a liquid detecting apparatus; and wherein at least a portion of said liquid detecting apparatus is disposed at said container; said liquid detecting apparatus comprising: a liquid detecting circuit comprising an electrode unit formed by a pair of electrodes that is to be disposed in contact at least partially with the 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 an alternating-current signal source; wherein the liquid detecting circuit inputs an alternating-current signal not containing a direct-current component to the 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 based on the output signal; 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 wherein an electrode unit is provided in each of a plurality of containers, and wherein the liquid detecting circuit sequentially outputs, a status of electrical connection between each of the respective pairs of electrodes in the plurality of containers.