Theory of microinduction measurements

Abstract

The microinduction sensor consists of miniature transmitter and receiver coils and can be used to make a noncontacting conductivity measurement of inhomogeneous media. Theoretical models for the microinduction sensor are presented that make it possible to better understand the response of the sensor in a wide variety of circumstances. For example, the issue of resolution, depth of investigation, standoff, coil tilt, and effect of Maxwell-Wagner charge accumulation, are better understood using the model. A Green's function approach is used to formulate an integral equation whose lowest Born approximation and geometrical factor theory can be used to gain physical intuition and to predict the response of the sensor in certain special cases. To solve more general problems, a full wave theory for the sensor over a layered medium is introduced that includes all electrodynamic effects.