| 摘要 |
A method for measuring an insulation resistance of an electric line. A low frequency signal, which has the same frequency as a signal applied to the electric line and is in phase with the line applied signal or shifted by 90 degrees therefrom, is applied with the amplitude value being varied with a period T. A leakage current sent to synchronous detector is adjusted with respect to its phase or a reference signal is adjusted with respect to its phase to minimize (make zero) or maximize one of induced effective components or induced ineffective or reactive components of the leakage current having a frequency of 1/T.
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