ULTRASONIC RANGING
José Miguel Martín Abreu, R. Ceres, Teodiano Freire · Sensor Review · 1992
The pulse‐echo method used for the measurement of distances is based on the determination of the fly‐time, employed by the wave (a pulse or a short train) to travel from the sensor to the object and back. It is easy to measure with accuracy the precise moment of the emission, but determining the precise moment of the arrival of the echo is somewhat more complex.