Examples disclosed herein are directed to a method and apparatus for determining a position of a ring within a process kit. In one example, a sensor assembly for a substrate processing chamber is provided. The sensor assembly includes a housing having a top surface, a bottom surface opposite the top surface, and a plurality of sidewalls connecting the top surface to the bottom surface. The housing also has a recess in the top surface, the recess forming an interior volume within the housing. The sensory assembly includes a bias member, and a contact member disposed on the bias member. The bias member and contact member are disposed within the recess. A sensor is configured to detect a displacement of the contact member. The displacement of the contact member corresponds to a relative position of an edge ring.