Figure 1. Ultrasonic sensor working principle

From

Distance Measurement via Using of Ultrasonic Sensor

Michal Kelemen, Ivan Virgala, Tatiana Kelemenová, Ľubica Miková, Peter Frankovský, Tomáš Lipták, Milan Lörinc

Journal of Automation and Control. 2015, 3(3), 71-74 doi:10.12691/automation-3-3-6