A process applicable to an object consisting of a substrate made of ferromagnetic electrical conductive material covered with a non-ferromagnetic electrical conductive coating layer for product measurement layer conductivity times layer thickness.

摘要

PCT No. PCT/EP96/02627 Sec. 371 Date Mar. 16, 1998 Sec. 102(e) Date Mar. 16, 1998 PCT Filed Jun. 18, 1996 PCT Pub. No. WO97/01739 PCT Pub. Date Jan. 16, 1997Method, applicable to an object consisting of a substrate made of ferromagnetic electrically conductive material covered with a layer of a non-ferromagnetic electrically conductive coating, for measuring the product of the layer conductivity times the layer thickness, consisting in placing at least one inductor producing a variable magnetic field in a space neighboring the object, in measuring, by means of a detector consisting of at least one bounded detection surface, two quantities proportional to the parts of the time derivative of the magnetic flux created in the detection surface concomitantly by the inductor and by the object, in phase and in quadrature with a reference electrical signal, in concomitantly employing two different functions of these two measurements by defining an experimental point by taking these two functions as the two input quantities of a first chart which cannot be reduced to an equivalent chart with a single input, which is independent of the conductivity of the layer and of the conductivity and the permeability of the substrate, but is dependent on the characteristics of the inductor/object/detector system and on the variable magnetic field produced by the inductor, the said chart consisting of a network of non-secant curves which each correspond to a different value of the product of the layer conductivity times the layer thickness, and in determining on the chart which of these curves passes through the point corresponding to the measurement and deducing therefrom the value of the product of the layer conductivity times the layer thickness.