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Thickness measurement of moving nonmagnetic metal foil by impedance variation
Author(s) -
Ishida Koichi,
Itaya Toshiya,
Tanaka Akio,
Takehira Nobuo,
Miki Toshikatsu
Publication year - 2012
Publication title -
electrical engineering in japan
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.136
H-Index - 28
eISSN - 1520-6416
pISSN - 0424-7760
DOI - 10.1002/eej.21269
Subject(s) - electromagnetic coil , conductor , materials science , electrical impedance , inductance , foil method , electrical conductor , eddy current , skin effect , acoustics , electrical engineering , condensed matter physics , mechanics , nuclear magnetic resonance , physics , composite material , engineering , voltage
Abstract When an AC‐excited coil faces a nonmagnetic moving metal foil, an eddy current is induced in the conductor and the coil impedance is influenced by the speed and thickness. By examining the speed and thickness characteristics, a coil can be used as the thickness sensor. In this paper, we derive rigid theoretical formulas for the magnetic field and coil impedance of a circular coil facing a stationary or moving foil conductor. We also present several characteristics with regard to the coil inductance and resistance based on calculations. The good agreement between the theoretical and measured values demonstrates the validity of the method. We found that the speed has no influence at a thickness in the tens of micrometers, and that the upper limit of the exciting frequency is 1 kHz. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(1): 15–23, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21269