ABSTRACT
The position of the sensor with respect to the exciter determines whether testing is done in the close or remote field. In close-field inspection, the sensor is placed so as to share at least some of the flux from the primary (exciter) coil. In remote field eddy current testing (RFEC), it is well removed from the source, and is not constrained by the need to remove the effects of the applied signal. The technique, originally used for oil well casing inspection. 10 − 13 is now used more generally. Unlike conventional EC, it is a through-wall technique. It responds to pits, cracks, 16 general thinning, and variations in permeability and conductivity, and has equal sensitivity to internal and external anomalies 14 , 15 for both ferrous and non-ferrous pipes.
