Method and apparatus for head fly height measurement

A method of measuring fly height of a head over a rotatable magnetic disc having a disc surface on which data is digitally stored by selectively polarizing portions of the disc surface into at least a first magnetic state or a second magnetic state, with the head coupled to a read back circuit that generates an electrical read back signal which contains pulses in response to the head encountering a transition between magnetic states, the method comprising:

• (a) measuring a pulse width and an amplitude of the read back signal;
• and
• (b) calculating the fly height of the head based on the measured pulse width and amplitude of the read back signal.

A fly height measurement system comprising:

• a head positioned over a rotatable magnetic disc having a disc surface on which data is digitally stored by selectively polarizing portions of the disc surface into at least a first magnetic state or a second magnetic state, with the head coupled to a read back circuit that generates an electrical read back signal which contains pulses in response to the head encountering a transition between magnetic states;
• and
• means for calculating the fly height of the head over the rotatable magnetic disc by measuring a pulse width and an amplitude of the read back signal and determining the fly height of the head based on the measured pulse width and amplitude of the read back signal.