- The paper deals with the evaluation of magnetic fields in a system of a relatively long-conductive ferromagnetic strip with nonlinear characteristic. The field is produced by an a.c. excited relatively short coil wound around the strip. The investigated system is similar to a magnetic field sensor system (described recently) which employs nonlinear eddy current effects in the sensing process. The analysis in the paper depends on linearization of the magnetic vector-potential equations by assuming that all field components are sinusoidal everywhere, and by imposing an appropriate change of μ with the material depth. The linearization process enables the integration of the field equations by Fourier transform. The evaluated results compare favorably to experimental results.