Patent ID: 8082785
Filing Date: 2011-12-27
Classification: G01F

Abstract:
1. A liquid-level sensor comprising: a shaft that extends along an axis in a vertical direction in a liquid holding tank; a float positioned to move along the shaft with changes in liquid height within the tank wherein the float includes at least one conductive element for interaction with a fluctuating electrical field; wherein the shaft has a set of axially-spaced, electrically independent conductive loops positioned so that different loops are proximate to the conductive element for different liquid heights, an oscillator circuit connected to the electrically independent conductive loops to apply an oscillator signal to the loops producing a fluctuating electrical field proximate to the loops; a demodulator circuit connected to the electrically independent conductive loops to detect a change in current flow caused by interaction of the conductive element with a fluctuating electrical field for a given loop; and a decoder circuit communicating with the demodulator circuit to provide a liquid-level output signal indicating a liquid-level height based on an identification of the given loop.