Object-Property-Based Differential Eddy Current Gap Sensing Device

To improve the sensitivity of thin eddy current device to measure the gap in small interlayer structure, an object-property-based differential structure is designed. The object-property-based differential eddy current gap sensing device has negative lift-off effect element (NLOEE) and positive lift-off effect element (PLOEE). The object in NLOEE/PLOEE is made of soft-magnetic material/nonmagnetic or hard-magnetic material, which results in a reduction/an increase of the NLOEE/PLOEE coil inductance with the increaese of the lift-off. Through using NLOEE and PLOEE as the neighboring arms of an electrical bridge, the conversion from the lift-off to the voltage is realized. The results show that the sensitivity can be improved using the object-property-based differential structure.