Detection of Modulation and Contact at HDI With Electrical Current

In the present work, a novel technique for detecting head-disk contact and modulation is presented. The technique involves measuring electrical current at HDI in the ultra-low flying cases. It is found that the electrical current is very sensitive to head-disk contact and head modulation, which are confirmed with Guzik measurements. Acoustic emission (AE) is also used in the same measurements for contact detection and found to be less sensitive than the electrical current. The electrical current at HDI can be generated through either the tribo-charging/discharging at HDI or externally applied bias voltage. Potential applications of this technique for both head modulation/contact testing and disk glide testing are discussed.