APG LOE Master Sensor user manual - Manual (Page 4)

LOE Series Rev. B, 1/12
4
Automation Products Group, Inc.
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• Understanding Ultrasonics
Ultrasonic sensors use a transducer to transmit bursts of ultrasonic sound
waves. Each burst contains a series of pulsed sound waves that emit in the
shape of a cone, refl ect off the target, and are detected by the sensor. The me
required for the sound waves to travel to and from the target is converted into
a distance measurement by the sensor. Ultrasonic sensing is aff ected by several
factors including the target surface, distance, size, and angle. The following
considera ons will help ensure the best possible target condi ons.
Surface
The ideal target surface is hard and smooth. This type of surface will refl ect a
greater amount of signal than a so or uneven surface. Sound wave absorbent
materials, such as granules and powders, will reduce the opera ng range of the
sensor and decrease measurement accuracy.
Distance
Sound wave a enua on increases as the distance traveled increases.
Therefore, targets at longer ranges require be er refl ec ve characteris cs than
targets that are closer to the sensor.
Size
A large object will have a greater surface area to refl ect the signal than a
smaller one. Therefore, a large target will be detected at a greater distance
than a small target. The surface area recognized as the target will generally be
the por on closest to the sensor.