Theoretical analysis of localized magnetic flux measurement by needle probe

Analytical study of the needle probe measurement of magnetic nux was performed on the basis of the electromagnetic theory to provide an advanced theoretical backbone for the measuring method. Provided that the nux change in the specimen is homogeneous, the electromotive force induced between the needles represents exactly the nux change in the area between the needles. The measuring error in the needle probe measurement is caused by lack of homogeneity in the nux change postulated in the theory. Among several possible causes of flux non-homogeneity, the existence of domain structure is most intrinsic in localized area measurements, so that in this study the measuring error due to this cause was calculated theoretically in detail It can be concluded that even in the cases of large domain size often occurring in oriented core materials, the localized measurements by the needle probe provide fairly reliable measure of the nux change in the area.