| 摘要 |
PURPOSE:To raise properly alarm about dogging of a magnetic head by providing a means detecting a drive current of a servo motor corresponding to a torque at the normal running state and a means raising alarm when the drive current reaches a prescribed value or over. CONSTITUTION:If blinding of the head takes place, the load torque of the servo motor 2 is increased by 2-3 times more than the normal state. Since the load torque is detected as a motor current, a voltage comparator 12 compares a voltage equivalent to the present load torque across a resistor 9 with a voltage twice the voltage equivalent to the normal torque across a variable resistor 13. An output terminal of the voltage comparator 12 connects to an input terminal of a AMD gate 14 having other input terminal to a signal exemping a transient torque at the start and stop of the servo motor 2. When the voltage comparator 12 gives an output L to AND gate at the normal running, an alarm signal is outputted as an output of the AND gate 14. |
