JPS61186881A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE: To improve the ability to detect a reflected wave from very short distance by providing a gate circuit, a gate timing varying circuit, a position decision means, etc.

CONSTITUTION: The gate timing varying circuit 10, gate circuit 14, the 2nd gate circuit 16, etc., are provided. The 1st ultrasonic wave of one shot generates a corresponding ultrasonic wave unless there is a reflection waveform in a short-distance zone. The circuits 16 and 14 are triggered with this signal to operate. When a reflected signal from, for example, a body to be detected at short distance returns through the transmission and reception of the ultrasonic wave of the 1st shot, a fine-level signal passed through a transmitter receiver 7 is amplified 8 by a receiving circuit 2 and further selected by a tuning amplifying circuit 9. The signal from the circuit 9 is detected by a detecting circuit 11 and a level detecting circuit 12 operates when the signal is higher than an operation level. When this reflected wave is generated within the time when the gate of the circuit 16 is open, the circuit 16 outputs a signal. Therefore, a reverberation component becomes short corresponding to the shortening of the transmitted signal and the ability to detect the reflected wave is improved.

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