In situ measurement of flyheight variations in magnetic storage devices through the use of sample margin signal processing techniques

An analysis technique that characterizes magnetic disk drives that use sampling detectors has been developed. This test scheme is analogous to the window margin test for drives that use peak detect channels. The test methodology is called sample margin testing. As with window margin testing, this scheme can be used as a short cut to error-rate testing in development and manufacturing environments. Due to the simplicity of digital compared to analog signal processing, sample margin data can be obtained in situ for an operating disk file. The sample margin data are periodically taken and compared to previous measurements to determine projected changes in error rate. Recording anomalies, like magnetic erasers and increasing flyheight, cause error-rate degradation and a corresponding decrease in the sample margin over time. This scheme can be used to monitor these physical changes. The use of this technique as an in situ monitor of mechanical disk file parameters is described