How does an eddy current probe work?
• When an AC current flows in a coil in close proximity to a conducting material the magnetic field of the coil will induce circulating (eddy) currents in the material • The magnitude and phase of the eddy currents will affect the loading on the coil and hence its impedance. • Note that to be detected cracks must interrupt the surface eddy current flow • Cracks lying parallel to the current path will not cause any significant interruption and may not therefore be detected Cracks in a material are one example of a factor that can affect the magnitude of eddy currents and which are therefore detectable by this method. Other factors include: • Conductivity • Magnetic permeability • Geometry – e.g.
