Embodiments of the invention relate to measuring characteristics of a head with an actuator put in a state of being pushed against a crush stop. In one embodiment, with a head placed on an innermost ID side or with the current of a VCM sustained at a magnitude I_mid, a burst pattern is written onto a recording disk. At this stage, the gain of a VGA is equal to its maximum value Gmax. Then, while the current of the VCM is being changed gradually, the gain of the VCA is measured. As the current of the VCM becomes equal to a magnitude I_center, a read element of the head is positioned right above the burst pattern. At that time, the gain of a VGA is equal to its minimum value Gmin. As the read element is further moved to the OD side, the gain of the VGA again becomes equal to the maximum value Gmax. A read/write offset of the head is identified by the magnitudes I_center and I_mid.