Abstract
The technique for detecting the head-disk contacts by using the read back signal was investigated. A spectrum of the read back signal was measured and the time history of the peak height at the recording frequency was monitored by using a spectrum analyzer to determine the fluctuation of the read back signal (peak to peak values and sigma values). The track average amplitude (TAA) and the acoustic emission (AE) signal were also monitored. The peak to peak and the sigma values proved to be sensitive enough to detect the slider-disk contact and so was the AE sensor. The TAA, however, was not sensitive enough. On the spectrum of the read back signal, some side band peaks were observed near the recording frequency when the slider was in contact with the disk. The differences in frequency between the peak of the read back signal and side band peaks showed the vibration mode of the head ginbal assembly (HGA) caused by the slider-disk contact.
