| 摘要 |
PURPOSE:To remove the influence of the variation of characteristics of a plurality of probes to downsize the title circuit and reduce its cost by performing the correction differing from probe to probe of the control of the distance between a medium and each probe in common to all probes through a correction circuit. CONSTITUTION:A control CPU 114 successively changes probes to be selected to perform the Z-direction control of all probes. For the period from the application of signal once to an actuator to that of signal again to the same actuator, further, the actuator is placed in a floating state. During this period, a control voltage is maintained by the interelectrode capacity of the actuator so that the displacement of the actuator is preserved. By the use of the so-called pipeline processing, then, respective operation/conversion circuits 103-108 can lower an operating frequency to a sampling frequency so that it is possible to contrive to downsize the title circuit and reduce its cost.
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