JPS6412284A - Ultrasonic range finder - Google Patents

Abstract

PURPOSE:To accurately measure a short distance and a long distance without being affected by the reflected wave of an obstruction from the short distance, by detecting the detection signal of the reflected wave on the basis of a detection signal attenuating with the elapse of time. CONSTITUTION:When the predetermined time ultrasonic signal from a transmitting circuit 1 is emitted to an object A to be measured from a head 3 through a change-over circuit 2, the ultrasonic signal is reflected from the object A to be measured to be received by the head 3. At this time, when an obstruction A' is present on the way up to the object A to be measured, the reflected wave from the obstruction A' is also received. In this case, each receiving wave is amplified by an amplifying circuit 5 through the change-over circuit 2 and subsequently inputted to a BPF to remove a noise component and further shaped by a shaping circuit 7. When a detection signal is detected on the basis of a trigger voltage signal attenuating with the elapse of time, the rectifying waveform accompanied by the object A to be measured can be clearly discriminated regardless of long and short distances and accurate measurement can be performed.