Lift-off and tilt effects on eddy current sensor measurements: a 3-D finite element study

The eddy current sensor method is widely used to evaluate conductive parts. The eddy current measurements are very sensitive to the variations of the sensor positioning relatively to the part under evaluation, which can disturb consequently such evaluation. The effect of the variation of the positioning of a sensor having an U-shaped magnetic core has been studied by 3-D finite element computations. The results show that the tilt and the lift-off of the sensor relatively to the part under evaluation induce similar straight lines in the normalized impedance plane. Consequently their effect can be corrected fairly thanks to a single processing. This notably allows to reduce the sensor handling during its calibration as well as the calibration time.