PURPOSE: To 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. Below is the signal seen by the oscilloscope with the horizontal scale at 10 ms/division (left) and at 100 microseconds per division (right).

SUGGESTIONS: Set the motion detector to go for a long time (one minute or more) so that you have time to adjust the oscilloscope and view the signal. the

REFERENCES: (PIRA unknown.)

EQUIPMENT: Computer cart with ultrasonic motion detector activated, oscilloscope with lecture hall microphone and amplifier, as photographed.

SETUP TIME: 5 minutes.