These eddy currents build up their own magnetic field (secondary field) superimposing the primary field. Consequently, the impedance of the coil changes.

This impedance variation carries information of the electromagnetic properties of the material and the geometry of the system under inpection.

 

 

Impedance plane

Resistance R

The impedance of the coil is changed by the eddy current‘s magnetic field

Impedance of the coil in air

Impedance of the coil on material

An ac fed coil builds up an alternating magnetic field (primary field). This field is encircled by an electrical field (law of induction).

 

 

Eddy current inspection with EddyCation

In a conductive body this alternating electrical field drives eddy currents.