US Patent 7616326 Proximity-leveraging, transverse displacement sensor apparatus and method

A system for determining the longitudinal position of a displaceable element positioned between two substantially orthogonally laterally opposing displacement sensors measures a distance from each displacement sensor to the displaceable element. The displaceable element has a tapered thickness along its length. A change in the longitudinal position of the displaceable element causes the proximity sensors to each detect their distance to the displaceable element, which distances then correspond directly to the local thickness and thus the longitudinal position of the displaceable element. The system calculates the position of the displaceable element. The system can easily factor out errors in measured lateral proximity position of the displaceable element, since an erroneous proximity to one sensor is equal and opposite to an erroneous proximity to the other.