Two calibration methods of AE measurement channels for slider-disk contact detection

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