An analytical model of the effect of external DC magnetic fields on the AC voltages of an LVDT

An analytical model to describe the effects of an external DC magnetic field on the harmonics amplitude of the secondary voltages of a Linear Variable Differential Transformer LVDT is proposed. A very general approach is used based on the introduction of the equivalent differential permeability concept that takes into account the sensor's geometry as well as the magnetic properties of its materials. The focus is mainly on the nonlinearity of the material of the LVDT's core since it is the material with the highest permeability. The proposed model is finally validated by means of measurements performed on a prototype explicitly built for that purpose.