DISTANCE MEASURING DEVICE

摘要

PURPOSE:To measure accurate distance through a simple ciruit with an ultrasonic wave pulse by sampling and holding a receive signal at every oscillation period, comparing two successive signals to decide the arrival time point of a reflected wave when the signal comparison is reduced. CONSTITUTION:An ultrasonic wave pulse radiated by an ultrasonic wave oscillator 11 is reflected by a target to enter a receiver 12. The receive signal is inputted to the 1st sample-and-hold circuit 103 to hold the maximum in every oscillation period with an analog switch 103A successively, and it is outputted from an amplifier 103B as a hold signal 1h. The signal 1h is held in a holding circuit 104 as the 2nd hold signal 1i elasping a specific time after sampling timing. The signals 1h and 1i are compared with each other by a comparing circuit 105, which outputs a peak detection signal when the signal 1i becomes larger to measure the time of reflected wave arrival.