Study of head/disc interface dynamics using a thermal asperity sensor

Thermal asperity (TA) sensors have been used to study head/disc interface dynamics. TA sensor voltage output fluctuates in proportion to the head to disc spacing changes directly above the sensor. Spacing fluctuations occur in response to system resonances and other excitations. By analyzing the frequency content of the TA sensor output, the excitation sources have been identified. The TA sensor is found to detect disc run out, micro waviness, disc flutter, suspension modes, air bearing resonance and slider body vibrations. Collapse of the interface, i.e., the unsteady slider dynamics, following collision with a "triggering asperity" is also investigated.