Eddy-current, or inductive proximity sensors, operate on the principle of electromagnetic induction [62,63]. As illustrated in
Fig. 23, an eddy-current probe consists of a coil facing an electrically conductive target. When the coil is excited by an AC current, the resulting magnetic field passes through the conductive target and induces a current according to Lenz’s law. The current flows at right angles to the applied magnetic field and develops an opposing field. The eddy-currents and opposing field become stronger as the probe approaches the target.