Inspection of Metallic Plates Using a Novel Remote Field Eddy Current NDT Probe

The remote field eddy current (RFEC) technique was invented in 1951 [1], [2] and is widely used as a nondestructive evaluation tool for inspecting metallic pipes and tubing. Essentially, the RFEC phenomenon can be observed when an AC coil is excited inside a conducting tube (see Fig. 1). The RFEC signal can be sensed by a pick-up coil located 2–3 diameters away from the excitation coil. The signal is closely related to the tube wall condition, thickness, permeability, and conductivity. The signal phase, especially, has approximately linear relationship with the tube wall thickness.