AN EXPERIMENTAL CORRELATION OF SLIDER-DISK CONTACT DETECTION BETWEEN PIEZOELECTRIC AND ELECTRICAL-RESISTANCE MEASUREMENTS

Piezoelectric transducers (PZTs) and Acoustic emission (AE) sensors have become widely accepted for measuring slider-disk contacts in magnetic media. Recent papers have shown that the 140 kHz and 160 kHz resonant frequencies reported with these methods are most likely a result of sensor resonances and not actual slider resonances, making the accuracy of these detection methods suspect. This paper presents two velocity avalanche methods which can be used to determine slider-disk spacing as well as to calibrate individual PZT sliders. The measurements, which were made using a specially developed asperity disk, indicate that the PZT signals must be high-pass filtered to provide accurate contact detection. When the PZT results are compared to electrical resistance methods it is shown that both methods detect given asperities at the same velocity (fly height) indicating that PZT detection is both sensitive and accurate.