Analysis of the liftoff effect of phase spectra for eddy current sensors

Wuliang Yin, Richard Binns, Stephen J. Dickinson, Claire Davis, Anthony J. Peyton

    Research output: Contribution to journalArticlepeer-review


    This paper presents an analytical model that describes the inductance change when a double air-cored coil sensor is placed next to a conducting plate. Analysis of the analytical model reveals that the phase signature of such a sensor is virtually liftoff independent. This finding is verified by numerical evaluations. This paper also finds that the phase signature of a ferrite U-cored sensor can be approximated by that of a double air-cored sensor of similar size and, therefore, possesses a similar liftoff-independent property. Measurements made with a sample U-cored sensor next to plates of nonmagnetic and magnetic materials verified the theoretical results. © 2007 IEEE.
    Original languageEnglish
    Pages (from-to)2775-2781
    Number of pages6
    JournalIEEE Transactions on Instrumentation and Measurement
    Issue number6
    Publication statusPublished - Dec 2007


    • Electromagnetic (EM) sensor
    • Liftoff
    • Nondestructive testing
    • Phase spectra
    • Steel microstructure monitoring


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