MEASUREMENT METHOD OF MAGNETIC DISK APPARATUS, AND MAGNETIC DISK APPARATUS
A gain controller changes a gain of a read amplifier depending on whether a head reads out servo data or user data. Further, a heater setting unit changes the temperature of a heater and a reading gain when detecting touchdown performed by the head. Accordingly, a dynamic range of AGC in a read-write channel is increased, so that error detection is prevented for touchdown that occurs because an AGC gain converged value remains at 0.
1 . A measuring method of a magnetic disk apparatus that has a preamplifier amplifying servo data for positioning-use with a servo data gain and amplifying user data stored in a user area available for reading and writing of given data with a user data gain, the measuring method comprising:
amplifying the user data with the user data gain;
evaluating an output level of the amplified user data;
changing the user data gain based on a result of the evaluating;
amplifying the user data with the changed user data gain; and
measuring a signal intensity of the user data.
2 . The measuring method according to claim 1 , further comprising:
changing a temperature of a head reading out at least one of the servo data and the user data so as to change a lift amount of the head from the magnetic disk surface, wherein
the measuring measures a change in the signal intensity due to a change in the temperature of the head.
3 . A magnetic disk apparatus, comprising:
a preamplifier that amplifies servo data for positioning-use with a servo data gain and amplifies user data stored in a user area available for reading and writing of given data with a user data gain;
an evaluating unit that evaluates an output level of the user data amplified by the preamplifier with the user data gain; and
a measuring unit that causes the preamplifier to change the user data gain and amplify the user data with the changed user data gain based on the evaluation by the evaluating unit, so as to measure a signal intensity of the user data.
4 . The magnetic disk apparatus according to claim 3 , further comprising a head temperature controller that changes a temperature of a head reading out at least one of the servo data and the user data so as to change a lift amount of the head from the magnetic disk surface, wherein
the measuring unit measures a change in the signal intensity due to a change in the temperature of the head.