| 摘要 |
An ultrasonic sensor includes a piezoelectric vibrator (1), a reverberation measuring device (5) and a compensating device (2a-2c, 5, 6, 8a-8c, 9a-9c, 10a, 10b). The piezoelectric vibrator (1) vibrates to transmit an ultrasonic wave, receives a reflected wave of the transmitted ultrasonic wave and produces an output signal corresponding to vibration of the piezoelectric vibrator (1). The reverberation measuring device (5) measures a reverberation period of the piezoelectric vibrator (1) from the output signal. The compensating device (2a-2c, 5, 6, 8a-8c, 9a-9c, 10a, 10b) compensates for an operation characteristic of the piezoelectric vibrator (1) in accordance with the measured reverberation period. Thus, the ultrasonic sensor can decrease a reverberation period, which may cause reduction in detection accuracy and impossibility of detection of an obstacle at a short distance.
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