| 摘要 |
PROBLEM TO BE SOLVED: To obtain a status equivalently at the time when an electrode having a large area is laid even if the area of an electrode is small by making an electrode to be arranged on one side of an impervious sheet in a circular form of a metallic wire. SOLUTION: For example, a impervious sheet such as synthetic resin sheet to be laid in a terminal disposal area is tested for breakage e.g. by using a plurality of electrodes 10 arranged two-dimensionally on the lower side of the impervious sheet and measuring a current flowing from an electrode provided on the other side of the impervious sheet to a selected electrode 10. The electrode 10 is formed in a circular shape such as ring of one to several meters in diameter for example, and a high potential can be obtained in the inside of the electrode 10, showing the same effect as that of a plate electrode having the same external shape. In addition, the electrode 10 of the circular shape is apt to be deformed different from the plate electrode, so fear for breaking the impervious sheet is small even if the ground varies because of earthquake, etc. The electrode 10 has a structure that two metallic wires are connected as to shortcircuit two points facing inwardly with each other.
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