DEVICE FOR COMPENSATING FLUCTUATIONS IN POSITION DETECTING SENSITIVITY

摘要

PURPOSE:To compensate the position detecting sensitivity by compensating the gain of automatic gain control means in a positional error detecting circuit in accordance with the position of a servo-head. CONSTITUTION:There is added a compensating circuit 20 which is equipped with not only an adder 13 and a D-A comparator 14 but also such a cylinder address resistor 12 as indicates the present position when the servo-head is kept stationary to position a track and as indicates the moving target track during the accessing operation and such a difference resistor 11 as indicates the number of left tracks to a target position and the moving direction during the accessing operation and as indicates 0 during other operations. Thus, the compensating voltage corresponding to the fluctuations due to the track position having the effective core width of the servo-head 1 is generated by the compensating circuit 20 and is fed through a wighing resistor 15 to a differential amplifier 7 so that the output of an adding circuit 6 is varied at the same ratio as the effective core width, thus maintaining the position detecting sensitivity costant.