The essential element of an eddy current meter is an inductor in a ferrite core. Typically there are two inductor and core assemblies: one located above and one located below the material to be tested. A current—oscillating in the low megahertz (RF) region—flows through the inductor coils, generating an oscillating magnetic field. When a conductive material is introduced between the two inductors and into the magnetic field, a circular flow of electrons (an eddy current) begins to move in the conductive layer due to magnetic induction. The difficulty of maintaining this eddy current is used to deduce the sheet resistance of the material being measured.