system and method of magnetically sensing the position of a piston rod moving relative to a cylinder

摘要

An apparatus, comprising: a cylinder; a piston rod movably coupled to the cylinder for movement with respect thereto; a magnetically hard layer formed on a surface of the piston rod to provide a recording medium, information being magnetically recorded in a plurality of regions of the magnetically hard layer to provide an encoding scheme for determining a position of the piston rod relative to the cylinder; a first plurality of magnetic field sensors positioned over one or more tracks of magnetically recorded regions to sense the magnetically recorded regions while the piston rod moves with respect to the cylinder; and a second plurality of magnetic field sensors for sensing ambient fields near the first plurality of magnetic field sensors for use in performing common-mode rejection. There is also a method for sensing a position of a piston rod moving relative to a cylinder.