Surface impedance tester

摘要

The permeability and resistivity of metal sheets including those installed in enclosing structures, are nondestructively determined by injecting a unit-step pulse of current into an exposed surface of the sheet and measuring the surface voltage gradient between a pair of contacts located between the current injection contacts. The permeability and resistivity of the metal determines the rate of diffusion of current into the surface and therefore the rate of decrease of this surface voltage gradient. At steady-state the current density will be uniform throughout the thickness of the sheet resulting in the surface voltage gradient stabilizing at a value depending on the resistivity and thickness of the metal.