SYMMETRY INSTABILITY of Thin-Film Magnetic Heads
Original Publication Date: 1988-Oct-01
Included in the Prior Art Database: 2005-Feb-15
In a magnetic disk storage, a magnetic head can be tested by erasing the disk in one magnetic direction and by writing a low-frequency track on the disk by means of the head. The head then reads the amplitudes of the positive and the negative pulses on the disk, the ratio of these amplitudes being indicative of the head's symmetry (writeability): SYMMETRY = + AMPLITUDES ____________ - amplitudes A well-performing head should be stable so that it performs in the same manner after each write operation. Unstable heads may have read errors which are caused by bit shifts if the readability deteriorates after a write operation. The known method of detecting unstable heads is to measure the pp (peak-to-peak) amplitude instability at one frequency.