| 摘要 |
PURPOSE:To remove a noise and to improve the quality of signals by differentially amplifying respective signals outputted from respective upper electrodes and comparing the amplified signals with a reference value to detect head crush. CONSTITUTION:The lower electrodes 14A, 15A of a pair of AE sensors 14, 15 are connected to an earth potential, respective signals outputted from respective upper electrodes 14B, 15B are differentially amplified by a differential amplifier 21 and passed through a band pass filter 22 to remove mechanical noise and electric noise and a signal in an objective signal band is selected and outputted. A signal outputted from the band pass filter 22 is led into a comparator 23 and compared with a threshold led as a reference signal and the compared result is outputted as an objective head crush signal.
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