EDDY CURRENT TESTING
History of Eddy Current Testing.
Eddy Current testing was brought into existence by two key scientists work; Michael Faraday's discovery of electromagnetic conduction in 1831 and Leon Foucault's discovery of eddy currents in 1851. Eddy Current Testing (ET) was further researched and refined and finally used for testing after WWII.
What is Eddy Current Testing?
A coil of conductive wire (probe) is excited with an alternating electrical current. The probe produces an alternating magnetic field around itself. The magnetic field oscillates at the same frequency as the current running through the coil, so when the coil approaches a conductive material, currents opposed to the ones in the coil are induced in the material — eddy currents.
Defects are found through ET because such defects or variations in the electrical conductivity causes a change in eddy current and a corresponding change in phase and amplitude that can be detected by measuring the impedance changes in the coil.