APG DCR-WEB user manual - Manual (Page 5)

Rev. A3, 10/08 DCR-WEB
5
Automation Products Group, Inc.
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• Understanding Ultrasonics
Ultrasonic sensors measure distance
using a transducer to send out
ultrasonic bursts. Each burst contains
a series of 1-20 pulsed sound waves
that emit in the shape of a cone,
reflect off the target, and are received
by the sensor. The time required for
the sound burst to travel to and from
the target is converted into a distance
measurement by the sensor.
Ultrasonic sensing is affected by
several factors including the target
surface, distance, size, and angle. The
following considerations will help
ensure the best possible target
conditions.
Surface
The ideal target surface is hard and smooth and perpendicular to the face of
the transducer. This surface will reflect a greater amount of signal than a soft,
sound wave absorbent surface. A target with poor sound wave reflection
characteristics will reduce the operating distance of the sensor and decrease its
detection
area
beam spread
low sensitivity
and
pulses
high sensitivity
and
pulses