Reference materials for calibrating magnetic permeability measuring equipment

The measurement and comparison of the relative magnetic permeability of weakly magnetic materials at different field strengths by an absolute method and by commercial instrumentation have been undertaken in order to provide reference materials for the calibration of these instruments. The absolute measurement method is described, the main types of commercial instruments are reviewed, and a variety of metals and alloys are examined for possible use as reference standards. The measurements are described, and typical results for permeability measurements using commercial instruments and the absolute method are given. The problems that the users of permeability measuring equipment encounter both in their calibration and in their operation are highlighted.< >