| 摘要 |
PROBLEM TO BE SOLVED: To surely carry out capacitance compensation for a piezoelectric vibrator in a supersonic sensor and hereby bring the reverberation time of reception output of the piezoelectric vibrator into a proper range. SOLUTION: A plurality of capacitors 2a-2c are connected in parallel to the piezoelectric vibrator 1. Further, a plurality of switches 3a-3c are provided for controlling the connection and disconnection between the capacitors 2a-2c and the piezoelectric vibrator 1 by switching the connection states between the capacitors 2a-2c and the piezoelectric vibrator 1. The combination of ONs and OFFs of the plurality of switches 3a-3c is changed in an output signal processing circuit 5 by sensing the reverberation time of the output of the piezoelectric vibrator 1 based on the reception signal from the piezoelectric vibrator 1, and outputting an ON-OFF control signal from a microcomputer 6 in accordance with the reverberation time. Thus, the capacitance compensation for the piezoelectric vibrator can be surely carried out and the reverberation time can be adjusted as desired. COPYRIGHT: (C)2005,JPO&NCIPI
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