Purpose and principle

Eddy current testing is a method used to determine material properties and to detect material defects. It is, for example, used in aircraft inspection.

  1. A coil supplied with alternating current generates an alternating magnetic field (primary field). This is surrounded by a circular electric field (induction law).
  2. In a conductive material, this alternating electric field induces circular currents known as eddy currents.
  3. These eddy currents generate their own alternating magnetic field (secondary field), which superimposes on the primary field and thereby changes the impedance of the coil. This impedance change is evaluated and contains information about the electromagnetic properties of the material as well as certain geometric properties of the test setup.
  4. The impedance of the coil is altered by the effect of the eddy currents!