System and method of determining relative position

A method of determining displacement of a movable member relative to a reference member, the movable member being configured for movement relative to the reference member along a range of positions in a first direction, comprising:

• providing a set of sensors;
• providing an array of encoded words on the movable member, the encoded words defining the positions of the movable member along the first direction, each encoded word including a plurality of indicia, each indicia being a multi-level logic unit configured as one of at least three states;
• moving the movable member relative to the reference member;
• sensing the indicia of an encoded word aligned with at least some of the sensors;
• and
• determining the displacement of the movable member along the first direction based upon the sensed indicia of the encoded word aligned with at least some of the sensors.

A system for determining displacement of a movable member relative to a reference member, the movable member being configured for movement relative to the reference member along a range of positions in a first direction, the system including a set of sensors and an array of encoded words, the encoded words defining the positions of the movable member along the first direction, each encoded word including a plurality of indicia, each indicia being a multi-level logic unit configured as one of at least three states, the system comprising:

• a controller configured to:
• sense the indicia of an encoded word aligned with at least some of the sensors;
• and
• determine the displacement of the movable member along the first direction based upon the sensed indicia of the encoded word aligned with at least some of the sensors.