Patent ID: 6624755
Filing Date: 2003-09-23
Classification: G01F

Abstract:
A liquid level sensor apparatus for determining the level of a conductive liquid held within a container having inside walls, one of which is an attachment wall, wherein the container is subject to the accumulation of residue as a consequence of the liquid contained therein, said sensor comprising:a first housing which is attached to attachment wall of the container; an insulated probe having an attachment end and a sensor end, wherein the attachment end of said insulated probe is connected to said first housing such that the sensor end is able to contact the conductive liquid held therein at a first predetermined level; a conducting sensor tip having a voltage and disposed at the sensor end of said insulated probe; a ground connection having an electrical polarity, said ground connection being in contact with the conductive liquid; a circumferential ring attached around said insulated probe adjacent to the attachment end of said insulating probe; wherein a bias voltage having the opposite polarity of said ground connection and having a voltage that corresponds to the voltage of said conducting sensor tip is applied to said circumferential ring; wherein once the liquid is in contact with said conducting sensor tip at the first predetermined level, a circuit is completed to said ground connection which indicates a â€œfullâ€  condition and wherein when said conducting sensor tip is not in contact with the liquid at the predetermined level, a â€œnot fullâ€  condition is indicated, and wherein the bias voltage on said circumferential ring prevents a false indication of a â€œfullâ€  condition by preventing the completion of circuit from said conducting sensor tip to said ground connection via residue on the container walls and said insulated probe even when the liquid is not in contact with said conducting sensor tip.