For the group assignment we have analyzed with an oscilloscope the signals from an HC-SR04 ultrasonic distance sensor. To get started we focused on understanding how this sensor works looking at various tutorials on the internet such as this one, as well as the HC-SR04 component date sheet.

Here below is presented our measurement setup :

Ultrasonic distance sensor - setup for signals analysis

And a screenshot from the oscilloscope that reveals the different signals observed from the ultrasonic distance sensor :

Ultrasonic distance sensor - signals analysis

This corresponds exactly to this picture extracted from the component datasheet:

HC-SR04 - timing diagram

The overall idea is that the length of the pulse in the Echo (green curve) varies depending on the distance measured by the sensor.