Two calibration methods of AE measurement channels for slider-disk contactdetection

Contacts between sliders and disks occur during normal operation in almost all current disk drives, and they can result in undesirable head crash, wea r failure, power consumption, or disturbance of the MR read-back signal. Th e acoustic emission (AE) method has been extensively utilized in the indust ry to detect these contacts and even to measure the contact force, but a su itable calibration for the AE measurement channel is lacking, Here, we prop ose two methods for obtaining an in-situ calibration of the AE channel base d on simultaneous Laser Doppler Vibrometer (LDV) measurements. One is the f orce identification method, from which one can obtain the impact force afte r the AE channel is calibrated. Another is the filter method, from which on e can obtain the velocity responses of the slider from AE. The two methods are successfully applied to quantitatively evaluate contact force.