Apparatus for measuring displacement and method of use thereof

A method of detecting the position of a magnetically susceptible element, the method comprising the steps of:

• (a) providing a primary coil wound around a longitudinal axis and at least one secondary coil wound around the longitudinal axis at a variable winding density distribution;
• (b) positioning a coupler along the longitudinal axis adjacent the primary coil and each secondary coil, the coupler including a resonating circuit configured to resonate at a resonating frequency;
• (c) exciting the primary coil with a first step of a signal;
• (d) receiving from each secondary coil a time varying signal having a ringing component superimposed on a time varying component temporally adjacent the first step of the signal;
• (e) acquiring one or more values of each time varying signal after the ringing component thereof dissipates;
• and
• (f) determining from the one or more values of each time varying signal a position of the coupler along the longitudinal axis.

A displacement measuring sensor system, comprising:

• a first member extending along a longitudinal axis between a first end and a second end thereof,
• a primary coil and a secondary coil wound around the longitudinal axis of the first member between the ends thereof;
• a control system connected for exciting the primary coil with an excitation signal and for receiving a time varying signal from the secondary coil, the time varying signal including a ringing component superimposed on a time varying component temporally adjacent a transition of the excitation signal;
• a second member positioned adjacent the longitudinal axis and having a resonator which causes the secondary coil to generate the time varying component in response to the excitation of the primary coil with the excitation signal, wherein the control system delays sampling of the time varying signal until the ringing component thereof dissipates.