THE APPARATUS FOR MEASURING DISTANCE

摘要

This appts. for measuring distance and detecting object presence with ultrasonic sensor transmits signal wave periodically and evaluates received signal changes. A source emitting a signal wave periodically contains two scillators operating at different frequencies and in a fixed phase relationship. The received signal is sampled and stored during a transmission period. The sampled signal is compared by the evaluation device with the previously stored signal. The scanning pulse width is no larger than the duration of operation of the higher frequence oscilation.