Eddy Current Testing (ET)

Method of using electromagnetic induction to detect flaws in electrically conductive materials.

Continuous wave eddy current testing is one of several Non-Destructive Testing methods that use the electromagnetism principle. Conventional eddy current testing utilizes electromagnetic induction to detect discontinuities in conductive materials. A specially designed coil energised with alternating current is placed in proximity to the test surface generating changing magnetic-field which interacts with the test piece producing eddy current in the vicinity. Variations in the changing phases and magnitude of these eddy currents is then monitored through the use of receiver-coil(s), or by measuring changes to the alternate current flowing in the primary excitation-coil. The electrical conductivity variations or magnetic permeability of the test piece, or the presence of any discontinuities, will cause a change in eddy current and a corresponding change in phases and amplitude of the measured current. The changes are shown on a screen for easy interpretation.