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Relative Permeability Measurements for Metal Detector Research



Michael D. Janezic, James R. Baker-Jarvis


We examine a measurement method for characterizing the low-frequency relative permeability of ferromagnetic metals commonly used in contraband materials. Besides the conductivity and geometry, the metal's relative permeability is another important variable in the detection of metal weapons. We describe a measurement method for measuring the relative permeability of metal toroid samples of rectangular cross section. Taking into account the finite conductivity of the metal and skin depth, we present a model for the inductance of a wound toroid, from which the permeability can be calculated. Relative permeability results are presented for ferritic and martensitic stainless steels as a function of frequency and magnetic field strength.
Technical Note (NIST TN) - 1532
Report Number


Conductivity, loss factor, magnetic response, metal detector, permeability.


Janezic, M. and Baker-Jarvis, J. (2021), Relative Permeability Measurements for Metal Detector Research, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD (Accessed July 19, 2024)


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Created October 12, 2021