Purpose:Show the wave form of the ultrasonic signal created by the ultrasonic motion detector.
Description:A microphone is used to pick up the signal from the ultrasonic motion detector; that signal is then amplified and viewed using an oscilloscope. The wave form consists of bursts of 45 kHz ultrasound at intervals of about 25 milliseconds. Above is the signal seen by the oscilloscope with the horizontal scale at 10 ms/division (left) and at 100 microseconds per division (right).
A question for students: Why do motion detectors use such high frequencies?