Eddy current sample characteristic measuring method and the eddy current sensor

摘要

PROBLEM TO BE SOLVED: To solve the problem that an eddy current is continuously produced in the sample and causes the temperature of the sample to be raised by the Joule loss due to the eddy current if AC voltage is continuously applied to a sample for a long time, and that the electric characteristics of the sample cannot be measured under a desired temperature condition and an error is produced even in the identification of a physical state such as film thickness or a crack.;SOLUTION: The temperature rise of the sample caused by measurement is avoided to the utmost using no continuous AC but using a single pulse minimizing the generation of heat value in the sample in the application of voltage to the sample to enhance measuring precision. The generation of single pulse voltage is performed by suddenly reducing the electric current allowed to flow to a coil. The loss of the eddy current of the sample during a single pulse voltage generation period is measured on the basis of the difference between the excitation energy of the coil before the generation of the single pulse and the energy regenerated through the coil during a pulse generation period.;COPYRIGHT: (C)2011,JPO&INPIT