Abstract: An apparatus is disclosed comprising a thermal sensor operable to detect at least one protrusion defect and at least one recess defect on a disk, the thermal sensor operable to generate a sensor signal. An attack time of the sensor signal is measured when the thermal sensor passes over one of the protrusion defect and the recess defect, and the protrusion defect is discriminated from the recess defect based on the attack time.

Abstract: A calibration disk for calibrating the fly height of a head, includes spaced circumferencial bands on the disk extending in a concentric fashion from adjacent an outer diameter of the disk to near an inner diameter of the disk. Each of the bands include radial and circumferencial spaced asperity emulating bumps having a population sufficient to produce a constant and continuous output signal from a glide head when the glide head flies lower than a maximum height of the bumps. The height of the bumps within individual bands are substantially uniform, and the average heights of the bumps in each band differ from each other. The configuration of the bumps on the calibration disk advantageously avoids errors caused by disk waviness, runout, and contamination. Further, using the differing heights of the bumps on the calibration disk, a glide head can be calibrated on the glide tester without using an independent fly height measurements for the glide head.