CPC B06B 1/0215 (2013.01) [B06B 1/0692 (2013.01); B06B 2201/40 (2013.01)] | 13 Claims |
1. An ultrasonic apparatus comprising:
a three-terminal ultrasonic transducer including a common electrode, a transmitting electrode, and a receiving electrode independent of the transmitting electrode;
a transmitting circuit to output a driving signal to the transmitting electrode to cause the ultrasonic transducer to transmit ultrasonic waves;
a receiving circuit to receive a receive signal from the receiving electrode; and
a capacitance measuring circuit that measures an electrostatic capacitance of the ultrasonic transducer while being electrically connected to the receiving electrode; wherein
the transmitting electrode is separated from the receiving electrode; and
the capacitance measuring circuit includes:
an alternating-current signal generating circuit to generate an alternating-current signal of a reference amplitude having a frequency different from a resonant frequency of the ultrasonic transducer;
a reference capacitor connected between the alternating-current signal generating circuit and the receiving electrode;
an amplitude measuring circuit to measure an amplitude between the reference capacitor and the receiving electrode; and
a capacitance calculating circuit to calculate the electrostatic capacitance of the ultrasonic transducer based on the amplitude measured by the amplitude measuring circuit and the reference amplitude.
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