| 摘要 |
PURPOSE:To attain a highly accurate detection by making coincident the main resonance frequency of an output signal induced to a piezoelectric transducer and the frequency of the sum or difference of the main resonance frequency of the output signal of a local oscillator with the central frequency of a BPF. CONSTITUTION:On a floating type magnetic slider, a piezoelectric transducer 1 is loaded. In order to execute the contact detection between a head and media, the frequency of an oscillator 11 is set so that the frequency of a local oscillator 11 and the frequency of the sum or difference of the main resonance frequency of the output signal induced to the transducer 1 can be coincident to the central frequency of a BPF 13. Thereafter, by an envelope detecting circuit 5, a comparator 6 and a counter 8 to count the number of a wave to exceed a threshold voltage, the number of times of the contact between the head and media is counted. Thus, the output of the erroneous contact detecting signal can be eliminated and the highly accurate detection can be executed.
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