Patent ID: 8549911

Claim:
A liquid-level sensor comprising: a guide that extends along an axis adapted to be positioned in a vertical direction in a liquid holding tank; a float positioned to move along the guide with changes in liquid height within the tank wherein the float includes at least one magnetic element applying a magnetic field to the guide, the magnetic field moving along the guide with movement of the float; wherein the guide has a set of axially-spaced magnet sensors switching between an unactivated state and an activated state upon exposure to the magnetic field, wherein the magnet sensors are positioned along the guide so that movement of the magnetic float activates a new magnet sensor before deactivation of an adjacent previously activated magnet sensor; further including an electrical circuit communicating with the magnet sensors to provide a signal being a function only of the state of an uppermost activated magnet sensor, the electrical circuit providing resistors connected to the magnet sensors; whereby the signal is monotonic with movement of the float; wherein each magnet sensor is a set of multiple magnetic reed switches, each magnetic reed switch having first and second switch terminals electrically connected and disconnected by operation of the reed switch, the reed switches wired in parallel so that all the first terminals of the parallel reed switches within each given sensor are electrically connected directly to each other and all the second terminals of the parallel reed switches within each given sensor are electrically connected directly to each other and wherein the connected first terminals of each sensor are connected to a different node of a network of the resistors; wherein each reed switch of a sensor is displaced axially from other reed switches of the sensor.