Importance

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Abstract

A method for detecting a leakage position in an impervious sheet, which comprises disposing a first and a second electrode units on an upper side and a lower side of the impervious sheet, respectively, the first electrode unit intersecting with the second electrode unit; short-circuiting all of electrodes in the first electrode unit; selecting a plurality of electrode sets one set after another set in the second electrode unit, each set comprising three electrodes adjacent to each other; supplying an AC voltage from an AC power source across a central one of each electrode set and the short circuited electrodes of the first electrode unit; measuring a potential difference between the other electrodes in the each electrode set to produce a measured voltage signal; and phase-detecting the measured voltage signal with a signal synchronized with the AC voltage from the AC power source to produce a detected signal, a series of the detected signals produced one after another changing in polarity due to a damage existing in the sheet, whereby a first position of the damage being detected on a one dimensional coordinate in an extending direction of the first electrode unit. Thereafter, the similar operation is carried out by replacing the first and the second electrode units by each other to obtain a second position of the damage on a one-dimensional coordinate in an extending direction of the second electrode unit; and defining a two-dimensional position of the damage from the first and the second positions.

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First Claim