Patent ID: 8106650
Filing Date: 2012-01-31
Classification: F15B,G01D

Abstract:
1. A position-sensing system, comprising: a cylinder; a piston rod movably coupled to the cylinder for movement with respect thereto; a magnetically hard layer formed on the piston rod to provide a recording medium, a plurality of rings around the piston rod being magnetized in the magnetically hard layer, each magnetized ring including a plurality of magnetized regions with neighboring magnetized regions within a given magnetized ring having opposite magnetic polarities, the magnetic polarities of the magnetized regions within each magnetized ring forming a magnetic pattern, and neighboring magnetized rings having opposite magnetic patterns; a plurality of magnetic-field sensors coupled to the cylinder in proximity of the magnetically hard layer on the piston rod to sense the rings of magnetized regions, each of the magnetic field sensors sensing flux from each of the rings of magnetized regions as the piston rod is moving with respect to the cylinder and, in response to sensing the rings of magnetized regions, generating signals used to determine position of the piston rod; and read-head electronics measuring rotational movement of the piston rod based on a count of magnetic transitions.