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ULTRASONIC MOTION DETECTORS



The air resistance data will be posted shortly.

We discovered a very strange behavior of motion detectors. Facing our
linoleum floor, and collecting data at the rate of 10 samples per second,
the distance to the floor (3 m) was correctly measured. But it was not
correct at higher collection rates (for example 2 m instead of 3 at 20
samples per second). We called Vernier and they suggested that we cover
the floor with a piece of carpet. This cured the situation. How can this
strange effect be explained? The f of the ultrasonic waves is 40 KHz.

Ludwik Kowalski and Richard Hodson
P.S.
Previously posted air resistance data should be ignored; they were
collected without using the carpet.