| 摘要 |
PURPOSE:To protect a mgnetic head based on an information signal by converting the variance component of the position detection signal of the magnetic head into a DC signal to compare this DC signal with the reference value, and performing said protection of the head in case the amplitude of the fluctuation component of the position detection signal shows an abnormal level. CONSTITUTION:If a servo system is oscillated due to the generation of some fault, the amplitude of a position detection signal is increased Vs as shown in a figure A. This is due to the fact that a magnetic head is vibrated by the oscillation of the servo system. The signal Vs is converted into a DC signal corresponding to an AC component which has increased its amplitude via a DC preventing circuit 2 and a rectifying circuit 4. As a level of the DC signal is high, the integration output signal VA of an integration circuit 6 has a higher level than the refernce voltage VR. As a result, a comparator 8 delivers a signal of a logic level ''H'' and an oscillation detection signal VB informs a fault of the servo system. The signal VB is applied to a protecting device. This protecting device retracts the magnetic head to the surface of a magnetic disk. |
