Thickness measurement of non-magnetic steel plates using a novel planar triple-coil sensor. (October 2019)

• Record Type: Journal Article
• Authors: Lu, Mingyang; Meng, Xiaobai; Yin, Wuliang; Qu, Zhigang; Wu, Fanfu; Tang, Jiawei; Xu, Hanyang; Huang, Ruochen; Chen, Ziqi; Zhao, Qian; Zhang, Zhijie; Peyton, Anthony
• Is Part Of: NDT & E international. Volume 107(2019)
• Publication Date: 2019-10
• Subjects: Lift-off effect -- Single-frequency thickness measurement -- Eddy current -- Planar triple-coil sensor -- Non-magnetic steel plates; Nondestructive testing -- Periodicals; Contrôle non destructif -- Périodiques; Electronic journals; 620.1127
• DOI: 10.1016/j.ndteint.2019.102148
• Languages: English
• ISSNs: 0963-8695

Abstract

Abstract: In the eddy current testing, the impedance tested by the sensor is influenced by the lift-off between the sensor and the sample plate. Consequently, the thickness inferred from the measured impedance is also affected by the lift-off. In this paper, a novel planar triple-coil air-core sensor is designed, in which three coils (two excitation coils and one receiving coil) with different radii are co-axially arranged in the same plane. Based on this sensor setup, an algorithm for the thickness measurement of the non-magnetic metallic plate is proposed. By using the transmitter-receiver combinations and the proposed algorithm, the measured thickness is almost immune to the lift-off variation. Moreover, previously the measurement of thickness requires a complex frequency feature – peak frequency for the real part of the impedance, which is obtained from the multi-frequency impedance or inductance spectra (frequency-sweeping mode), while with the method proposed in this paper, only single frequency measurement is needed, hence relaxing the instrument and measurement requirements. This method has a potential of on-line real-time measurement of the thickness for non-magnetic steel plates.