| 摘要 |
PURPOSE:To detect an accurate voltage across poles without adding a superfluous floating capacity to said part across poles by connecting a voltage dividing circuit, a rectifying circuit, and a smoothing circuit near said part across poles and providing an insulation amplifying device on the input side of an A/D converter. CONSTITUTION:Voltage from an AC power source 1 to a part across 2 is divided by the output side resistor 15 and the input side resistors 4, 5 of a rectifying circuit 6, a few milliampere of current is inputted into the primary side of an insulation amplifier 14 via a smoothing capacitor 7 and a detecting line 3, and its secondary side voltage is inputted into an NC control unit 9 via an A/D converter 8. Due to high resistance value of resistors 4, 5, 15 and the presence of the rectifying circuit 6, it is not possible for a floating capacity 11 to flow back to the part across poles 2, and since the voltage has been converted into a DC voltage near the part across the poles 2, a signal which is being transmitted through the detecting line 3 is hard to be affected by induction. As the floating capacity which is connected to the part across poles 2 is thus reduced, a minute discharge current can be obtained if a floating capacity 10 near the part across poles is made smaller, improving the surface roughness on a machining surface.
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