Determination of the thickness of copper coatings on steel by measuring the impedance of a thin elliptic coil
2002 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 13, no 4, 510-519 p.Article in journal (Refereed) Published
When a thin elliptically shaped coil is placed above a flat plate with a coat of metal, the magnetic fields in the vicinity of the coil is altered by eddy currents in the plate and the coat. The thickness of the coat influences the magnetic field and can be determined by measuring the coil impedance. An electromagnetic model utilizing an elliptic cylinder coordinate system accounting for the coil impedance with different values on the numerical eccentricity and the coating thickness is described. The model is based on a potential formulation of the problem from which the magnetic vector potential and hence the impedance is evaluated. The derivation utilizes a proper choice of the transversal field, giving a scalar Helmholtz equation in which the solution to the boundary value problem is separated. The resulting integral equation is expressed in closed form in terms of Mathieu functions. Numerical calculations and experimental measurements show how the model can be used to model a steel surface with a coat of copper to find expected impedance as function of the coating thickness.
Place, publisher, year, edition, pages
2002. Vol. 13, no 4, 510-519 p.
elliptic coil, thickness measuring, eddy current testing, coil impedance
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-48917DOI: 10.1088/0957-0233/13/4/313OAI: oai:DiVA.org:liu-48917DiVA: diva2:269813