In medical or low conductivity electromagnetic induction tomography, a low frequency approximation (i.e. neglecting the diffusion effect) can significantly simplify the forward and inverse solutions. However, this approximation normally leads to the over prediction of the amount of eddy currents induced by the transmitter coil, and hence to an overestimation of the secondary voltage measured on the receiver coil. The reason is because the penetration of the field into the object is not correctly described and the skin effect is ignored. In effect, the theory assumes that the signal is coming from a larger-than-actual volume. This paper uses an exact analytical solution for a coil(s) near a stratified media derived from a full wave theory to evaluate the skin effect at a range of frequencies and compares it with a simple model which omits the skin effect. The error due to the approximation is evaluated and the highest frequency at which the approximation holds valid to within a defined error range is ascertained.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.