APG LPU-2428 user manual - Manual (Page 5)

Rev. A3, 11/08 LPU-2428
5
Automation Products Group, Inc.
APG...Providing tailored solutions for measurement applications
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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, angle, and the
environment. The following
considerations will help ensure the
best possible target conditions.
Surface
The ideal target surface is hard and smooth and perpendicular to the sensor.
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 accuracy.
detection
area
beam spread
low sensitivity
and
pulses
high sensitivity
and
pulses