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Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001

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12.4.4 Ultrasonic

· The reflection of sound waves can be used to detect parts or distances.

· These normally use frequencies above 20KHz which is above the normal human hearing threshold of 16KHz.

· These sensors are commonly,

1. electrostatic - uses capacitive effects. It has longer ranges and wider bandwidth, but is more sensitive.
2. piezoelectric - based on charge displacement during strain in crystal lattices. These are rugged and inexpensive.

· Good for sensing distances to most materials with surfaces perpendicular to the beam.

· Applications of these are similar to optical sensors.