The universal impedance diagram of the ferrite pot core eddy current transducer

Experimental results indicate that the shapes of normalized impedance diagrams of ferrite pot core eddy current transducers are independent of transducer design parameters, lift-off, and material resistivity. When reduced with respect to coupling coefficient, normalized impedance diagrams of this class of transducers are represented by a universal curve. This curve is functionally described by two relationships. The first is that between reactance and the lift-off angle (angle whose tangent is the ratio of the change in the imaginary component of the impedance to the change in the real component). The second is the linear relationship between the tangent of the lift-off angle and the dimensionless ratio of the mean core radius to the skin depth. The lift-off angle is independent of the coupling coefficient. The independence of the functional relationships from the design variables is significant in that an analytic model of this class of eddy current transducers would be greatly simplified by the omission of these variables