| 摘要 |
PURPOSE:To detect an object up to the closest distance by providing a waveform shaping circuit and a voltage comparing circuit for an ultrasonic wave and masking voltage of a sneak wave by the waveform shaping circuit and taking out only the voltage of a reflected signal. CONSTITUTION:A pulse is generated by a timing circuit 1, and the waveform obtained by amplifying it is impressed to a transmitter 3 and is radiated as ultrasonic pulse to the space. A voltage comparing circuit 9 which compares the output voltage of the waveform shaping circuit 5 and the voltage of the reflected signal 16, which is received when said ultrasonic pulse is radiated to the object 15 to output is provided not to make malfunction the voltage of the reflected signal 16 and the output voltage of a sneak wave 17 inputted directly to a receiver 6, and the voltage of the sneak wave 17 is masked with the output voltage of the circuit 5 to take out only the voltage of the reflected signal. Thus, the object 15 is detected surely even if the object 15 exists near transmitter and receiver 3 and 6, and the non-detection range is eliminated. |
