In-Situ Contact Potential Measurement in Hard Disk Drives Using Head Disk Interface Voltage Control

There is an inherent contact potential difference between the head and the disk surfaces in hard disk drives (HDD’s). Current HDD’s use thermal fly-height control (TFC) during read/write operations. In this study, we show a method to determine the contact potential for the head disk interface (HDI) using TFC technology. We utilize TFC to measure the flying height of the slider via touchdown power by applying a DC voltage bias to either the head or the disk or both. The DC voltage condition where the TFC clearance is maximized corresponds to the balancing of the HDI contact potential. In other words, the opposite polarity of that DC voltage bias condition is the HDI contact potential. Additionally, we show that the contact potential of HDI can be determined by either applying the DC voltage bias to the head or to the disk.