| 摘要 |
PURPOSE:To improve response by providing 1st and 2nd load balance system and controlling the duty ratio of a pulse current supplied to the 1st load balance system according to whether a current supplied to the 2nd load balance system is large or small and its varying speed. CONSTITUTION:A balance mechanism 2 is provided with the 1st load balance system which has a 1st force coil 3 and a 2nd load balance system which has a 2nd force coil 4. Further, the coil 3 is supplied with the pulse current which is generated by chopping the output current of a constant current source 6 by an electric switch 7 and corresponds to a set duty ratio, and the coil 4 is supplied with the current (i) obtained by passing the detection value (displacement of dish 1) of a displacement sensor 9 through a P.I.D controller 11, etc., and converting it into a current (i) by a power amplifier 12. This circuit (i) is passed through an output resistance R to have a voltage value, which is read in a microcomputer 5 to determine the duty ratio of the pulse current supplied to the coil 3. Then when the current (i) of, for example, the 2nd balance system is not within a measurement range, the duty ratio of the current supplied to the 1st balance system is varied at a high speed.
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