Inductively coupled position detection system

Claim 1

Non-contacting apparatus for generating electrical signals commensurate with the position of a moveable member comprising: a plurality of sensor coils, said sensor coils each having an axis; means supporting said sensor coils in a spacially displaced generally co-planar relationship with the axes thereof being substantially parallel and being substantially perpendicular to said plane, one of said coils being located in each quadrant of an X-Y coordinate system, a fifth axis generally parallel to said coil axes passing through the intersection of the X and Y axis of said coordinate system; magnetic field producing means, said field producing means including a drive coil having an axis, said drive coil axis being substantially parallel to said fifth axis when said field producing means is in a neutral undeflected position, said field producing means being at least in part moveable with respect to and without physical contact with said sensor coils about said fifth axis to vary the magnetic coupling between said field producing means drive coil and each of said sensor coils, the magnetic field produced by said field producing means drive coil partly encompassing all of said sensor coils at least in the neutral position of said field producing means; means for generating an alternating excitation voltage for said field producing means; means applying said alternating excitation voltage to said field producing means drive coil; means coupling the moveable member the position of which is of interest to said field producing means whereby changes in the magnetic coupling between said field producing means drive coil and said sensor coils will be commensurate with movements of the member; first switch means, said first switch means being electrically coupled to first ends of a first and a second of said sensor coils, said first and second sensor coils lying in adjacent quadrants of said coordinate system; second switch means, said second switch means being electrically coupled to first ends of the third and fourth of said sensor coils, said third and fourth sensor coils lying in adjacent quadrants of said coordinate system; means electrically connecting the second end of the first of said sensor coils to the second end of the third of said sensor coils; means electronically connecting the second end of the second of said sensor coils to the second end of the fourth of said sensor coils; means responsive to said alternating excitation voltage for providing a pair of out-of-phase switch means control signals; means delivering said control signals to said switch means whereby said switch means will be closed in synchronism with the induction of voltages in said sensor coils; and means responsive to the voltages passed by said switch means when in the closed state for providing a pair of output signals which in combination are indicative of the direction and amount of deflection of said field producing means relative to said fifth axis.