Magnetomechanical transducers utilizing resonant frequency shifts to measure displacement of an object

A magnetomechanical-resonant-frequency transducer system responsive to the strength of a d.c. bias field on a target comprising:

• a. means including a driving coil co-axial with said target for interrogating said target,
• b. generating means for generating an a.c. magnetic field within said coil to effect direct magnetic coupling between said ac magnetic field and said target, said ac magnetic field incorporating the resonant frequency of said target;
• c. means including a displaceable object, biasing means for generating said dc bias field and changing means for varying the relative displacement of said object and said target so as to vary the strength of said dc bias field on said target, thereby applying a variable d.c. bias field to said target to produce changes in the resonant frequency of said target that are correlated with displacement of said object;
• and
• d. detection means for detecting the resonant frequency produced in said target by the strength of said dc bias field.