Patent ID: 6842257

Claim:
A method for testing a magnetic disc to be used in a disc drive, the magnetic disc having a plurality of tracks, comprising the steps of: rotating the magnetic disc; scanning the magnetic disc along radial lines; storing a sequence of data points representing slopes of a plurality of tracks along the radial lines; operating on the stored sets of points to determine a measured average slope for each track of said plurality of tracks around an entire revolution of said each track to establish a representative slope for each of the tracks of the plurality of tracks; taking a radial moving average to establish a sequence of data points, each data point being an average for a plurality of the tracks, and each track is represented by its representative slope; taking a radial derivative of the sequence of data points on the surface of the disc; building a curvature profile of the disc; and comparing said curvature profile to a pre-established limit to determine suitability of the disc for use in a disc drive, wherein the step of taking a radial moving average comprises developing an average over a plurality of tracks sufficient in number to eliminate spikes from appearing in a subsequent step.