Glide-height disk-tester and method of operation

A method for glide-height testing of a disk having a generally smooth disk surface and a plurality of asperities projecting above the disk surface, the method comprising:

• rotating the test disk at a generally constant speed about an axis substantially perpendicular to the disk surface;
• maintaining an air-bearing slider near the surface of the rotating disk, the slider having a front end upstream of the air-flow induced from the rotating disk, a trailing end downstream from the front end, a contact sensor for detecting contact of the protrusion pad with an asperity, and a protrusion pad at the trailing end and movable toward the disk surface in response to electrically-resistive heating;
• applying electrical current to the trailing end of the slider in increasing current levels;
• monitoring the output of the contact sensor during the application of said increasing current levels;
• and
• recording the current level applied when a signal from the contact sensor is detected, said recorded current level being representative of the glide height of the test disk.

A method for calibrating a glide-height disk tester, the tester including a slider having a front end upstream of the air-flow induced from the disk when the disk is rotating, a trailing end downstream from the front end, an air-bearing surface between the front and trailing ends and facing the disk surface, and a protrusion pad at the trailing end and movable toward the disk surface in response to the application of heat, the calibration method comprising:

• providing a calibration disk having a generally smooth disk surface and a plurality of sets of calibration bumps, each set of bumps projecting above the disk surface a unique calibration bump height;
• rotating the disk at a generally constant speed about an axis substantially perpendicular to the disk surface;
• heating the protrusion pad to move the pad toward the disk surface while the disk is rotating at said constant speed;
• detecting when the protrusion pad contacts bumps in a first set of calibration bumps;
• recording the level of heat applied when contact with the first set of bumps is detected;
• repeating the steps of detecting and recording for each set of bumps;
• and
• correlating, from the recorded heat levels and corresponding bump heights, a heat level with a glide height.