APG MNU Slave Sensor user manual - Manual (Page 4)

MNU Series Ultrasonic Sensors Rev. B1, 5/13
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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.