Lift-off suppression based on combination of bridge and transformer signal conditionings of eddy current testing
Qiuping Ma, Gui Yun Tian, Bin Gao, Xiangyu Zhao, Gaige Ru, Haoran Li
Abstract
Lift-off is a challenging issue in electromagnetic non-destructive testing and evaluation, especially in eddy current testing. It seriously affects the detection sensitivity and quantification accuracy. This paper proposes a combined signal conditionings of differential eddy current structure based on bridge and transformer for lift-off suppression. It provides both amplitude and phase information via two signal conditionings for multiple parameter measurement. Specifically, a multiple parameters fusion response model is established according to equivalent circuits between the electromagnetic sensing coupling and lift-off. This model enables to greatly reduces the lift-off ambiguities from mixed signal since lift-off parameter can be eliminated and defect information is increased. In particular, it is suitable for irregular lift-off variation suppression with non-parameters adjusting. Different defect samples have been conducted to validate the proposed method.