Development of Permeability Measuring Instrument

Recent electronic devices often use nonmagnetic components with very small permeabilities of less than 1.010. It is difficult to measure the permeability of such materials using the usual techniques. In order to enable measurement in such cases, an improved instrument for permeability measurement was devised. In this instrument, which is based on a type of differential transformer, the material is magnetized by an exciting coil and the resulting magnetic response is detected. The response consists of two components, one from the magnetization and one from eddy currents. The distribution of the magnetization and the eddy currents within the material were estimated using the finite element method applied to analysis of electromagnetic fields. On the basis of this analysis, an improved instrument was developed which is capable of measuring permeabilities of less than 1.010 even in small-size components.