Accurate measurements of plate thickness with variable lift-off using a combined inductive and capacitive sensor. (March 2020)

• Record Type: Journal Article
• Authors: Salas Avila, Jorge R.; Lu, Mingyang; Huang, Ruochen; Chen, Ziqi; Zhu, Shuang; Yin, Wuliang
• Is Part Of: NDT & E international. Volume 110(2020)
• Publication Date: 2020-03
• Subjects: Combined inductive and capacitive sensor -- Lift-off -- Single-frequency thickness measurement -- Eddy current -- Non-magnetic metallic plates; Nondestructive testing -- Periodicals; Contrôle non destructif -- Périodiques; Electronic journals; 620.1127
• DOI: 10.1016/j.ndteint.2019.102202
• Languages: English
• ISSNs: 0963-8695

Abstract

Abstract: In eddy current testing, lift-off variations between sensor and sample plate affect sensor inductance and consequently inferred thickness. In this paper, a novel combined inductive and capacitive sensor is designed in which the output of the capacitive sensor can be used to infer the lift-off. An algorithm is proposed to combine the inferred lift-off and the inductance measurement for predicting thickness. The effect of lift-off variations is significantly reduced using this combined sensor approach. Compared to the multi-frequency thickness measurements in our previous work, this only requires a single frequency measurement for each of the capacitive and inductive modalities, leading to a relaxation of the instrument and measurement requirements.