Measurement of contact potential difference in head disk interface by readback signal spectrum

The contact potential difference leads to electrostatic interaction between the slider and disk in a hard disk drive. The effect of electrostatic force on slider’s flying height and flying stability becomes more significant with the decrease of flying height. A method of measurement of contact potential difference in head disk interface by readback signal spectrum is demonstrated in this paper. When a voltage with DC and AC was applied in the head disk interface, the amplitude of readback signal at the first harmonic frequency of applied AC voltage is proportional to the sum of contact potential difference and applied DC voltage. The contact potential difference in head disk interface is equal to the negative of DC voltage when the amplitude of readback signal at the first harmonic frequency is minimal.