| 摘要 |
PROBLEM TO BE SOLVED: To measure an earthing resistance highly accurately. SOLUTION: This earthing resistance measuring device 1 for measuring the earthing resistance of an earthing bar is equipped with a signal generation part 6 for generating an ac signal with a variable frequency, an output resistance 8 connected between a lead wire 14 and the signal generation part 6, a signal switching means 9 for outputting the voltage of a part selected from an output terminal part of the output resistance 8, an input terminal part thereof, and a zero-potential part, a synchronous detection part 10 for executing synchronous detection of the output voltage from the signal switching means 9 by the ac signal, and an operation control part 12. The operation control part 12 measures the earthing resistance based on a lowest-value dc voltage component Vmr generated by the synchronous detection part 10 and acquired by changing an ac signal frequency of the signal generation part 6 at the selection time of the output terminal part by the signal switching means 9, a dc voltage component Vmr∞generated at the selection time of the input terminal in the maintained state at the frequency, and a dc voltage component Vmr0 generated at the selection time of the zero-potential part in the maintained state at the frequency.
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