Patent ID: 8058867

Claim:
A system for determining the position of a movable member with respect to a fixed member, the system comprising: a movable member capable of axial movement within a range of axial positions; a first magnet secured to the movable member at a first axial position and associated with a first magnetic field; a secondary magnet secured to the movable member at a secondary axial position and associated with a secondary magnetic field; a sensor assembly comprising magnetic sensors arranged in an array on a fixed member, the array extending along a direction of the axial movement, wherein the array is arranged in a generally linear series with each magnetic sensor interspaced approximately a uniform amount from an adjacent magnetic sensor in the array; a first magnetic sensor spaced apart from the sensor assembly on the fixed member such that the first magnetic sensor detects the first magnetic field of the first magnet in a first state and an absence of the first magnetic field in a second state; and a data processor for determining an axial position of the moveable member based on at least one of the first magnetic field and a secondary magnetic field sensed by the sensor assembly.