An in Situ Measurement Method for Electric Potential at Head-Disk Interface Using a Thermal Asperity Sensor

The electrostatic force at head-disk interface (HDI) becomes increasingly significant when the head-disk clearance is dropping into 1 nm scheme. Therefore, detecting and eliminating the electric potential in the HDI is a critical task for hard disk drives. To that end, this paper proposed an in situ measurement method for electric potential at HDI using a thermal asperity (TA) sensor. When calibrating the electric potential, both dc and ac components of the external voltage were supplied to the disk. As a result, the output of the TA sensor to the first harmonic of the ac component was linearly increasing with the decrease in the dc components. Experimental results show that this method is more efficient and flexible than the traditional methods.