| 摘要 |
PURPOSE:To prevent the generation of a pin-hole so as to perform steady and accurate electric discharge by actuating a pH adjusting device so as to control to the specified range of pH at the initial discharge when pH of the processing fluid in water group which was inspected and measured misses the specified range. CONSTITUTION:A conductivity detector 10, a pH detector 11, a conductivity measuring circuit 12 and a pH measuring circuit 13 are provided for processing fluid to be supplied to the processing space 9 by a pump 8 and a pump 6 for ion exchange processing device 7 is driven and controlled by a pump controller 14 according to the signal from both measuring circuits 12, 13. And when pH of the processing fluid in water group to be used repeatedly through circulation, which is inspected and measured, misses the specified range, a pump is driven and controlled so that it may be within the specified range where pH is 6-7 or thereabout like that at the initial processing, therefore corrosive ion dissolved in the processing fluid can be removed sufficiently. Accordingly, the generation of pin holes due to the electrolytic action by this ion and the generation of centralized discharge can be prevented and steady/accurate electric discharge can be performed.
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