| 摘要 |
PURPOSE:To measure the dynamic characteristic of the disk without being influenced by the dynamic characteristic of an actuator and to know the dynamic characteristic of the actuator in accordance with the necessity by measuring the dynamic characteristic of a disk with different numbner of revolution. CONSTITUTION:The first memory device 11 to store the frequency analyzing result of an actuator in the first rotation OMEGA1, the second memory device 12 to store the frequency analyzing result of the actuator in the second rotation OMEGA2 and an arithmetic unit 13 to calculate the dynamic characteristic of the disk by using the result stored in these memory devices and the static gain of the actuator are provided. A picture forming device 14 prints and picture- forms the result calculated by an ALU 13. A disk 1 is rotated by the rotation OMEGA1, the output of a servo circuit 4 is frequency-analyzed by a spectrum analyzer 9 and stored into the first memory device 11. Earlier, the characteristic is in the same manner measured by the rotation OMEGA2 (for example, OMEGA2=2OMEGA1) larger than the next rotation OMEGA1 and stored into the second memory device 12. An arithmetic unit ALU 1 successively calculates and obtains the dynamic characteristic of the disk.
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