Method of controlling the position of a read/write head and apparatus for testing a read/write head

摘要

A method of controlling the position of a read/write head (4) relative to a disk (2) in a test apparatus (1) is disclosed. The test apparatus (1) has a positioner (7) for positioning the head (4). The positioner (4) has a sensor (12) for measuring the actual position achieved by the positioner (7). The method comprises generating a sensor signal (13) measuring the actual position achieved by the positioner (7); generating a position error signal (20) of the head (4) relative to the disk (2) detected at the head (4); high pass filtering (21) the head position error signal (20) and low pass filtering (14) the sensor signal (13) so that there is substantially no overlap in frequency between them; and, deriving a low frequency head error signal (24) from the head position error signal (20) corresponding to any drift of the head (4).