RESOLUTION-IMPROVING ELECTRIC CIRCUIT OF ULTRASONIC DISTANCE MEASURING DEVICE

摘要

PROBLEM TO BE SOLVED: To utilize a low frequency ultrasonic wave having wide measurable distance and directivity and provide resolution of high frequency band ultrasonic wave by comparing a received ultrasonic signal level for stopping a distance measuring count pulse with a determined threshold by use of a logarithmic amplifier type comparator. ;SOLUTION: A drive signal is transmitted to a pulse transmitting circuit 4 at fixed intervals by a control circuit 3, and a counting circuit 7 is also started. A transmitter 5 transmits an ultrasonic signal controlled by the transmitting circuit 4. A receiver 6 receives the ultrasonic wave and transmits it after amplification to a received wave shaping circuit 1. The received wave shaping circuit 1 shapes the received wave and inputs a received signal A to a logarithmic amplifier type comparator 2 as an integrated waveform. The logarithmic amplifier type comparator 2 receives the value regulated by a threshold generating circuit 8 as a threshold signal B and outputs a received wave detection signal C of a fixed interval when the received signal A exceeds the threshold. The counting circuit 7 stops the counting operation according to the received wave detection signal C and derives the distance from the counted value.;COPYRIGHT: (C)1998,JPO