The parameters determine the depth to which eddy currents penetrate into the material and hence
whether the method is more sensitive to far side defects. Standard eddy current measurement, i.e. coil
impedance measurement, thus remains sensitive to the surface only for magnetisable, i.e. ferritic
steel. Alterations of the parameter need to be sough to be also sensitive to far side defects, wall loss
or mid-wall defects. On the other side the possibility of eddy current testing to be used in any
conductive material represents a great advantage over magnetostatic methods, which are only
applicable for permeable material. Altogether three types of modifications can be identified to render
eddy current more versatile.