On the modelling of a Barkhausen sensor

A numerical model of a plain Barkhausen sensor is studied by means of the finite element method. The three-dimensional sensor consists of a magnetizing yoke, modelled as an C-core electromagnet. The planar test object is modelled as a thin plate and consisting of two or three layers, indicating a situation with a hardened layer, a transition zone and a soft layer. Simulations for the magnetic field are made for different frequencies and material combinations in the frequency plane, corresponding to a harmonic excitation of the electromagnet. All materials, including the C-core, are modelled as magnetic isotropic having a linear magnetic permeability in the constitutive relation. The magnetic flux density is computed on both on the surfaces of the planar test object and as a function of depth. The effect of lift-off is studied