Ultrasonic Sensors Knowledge (Part 2): Influences on the Sound Beam

A major reason to use ultrasonic sensors is their ability to recognize most materials and surfaces. Color is of no consequence and they can detect solids, liquids, or powders. Surface properties also have no effect on detection reliability. It does not matter if the surface is rough, smooth, high gloss, transparent, dirty, wet, or dry – a high-quality ultrasonic sensor delivers precise results.

The best reflection can be reached when level, smooth surfaces are positioned at right angles to the sensor surfaces. If the angle to the surface object is not 90°, the returning sound can be deflected away from the transducer, and it will no longer be detectable. Large angle deviations are possible when recording rough or uneven surfaces. The amplitude of the reflected ultrasonic signal must be high enough to allow reliable measurement. Similarly, high levels of dust and humidity reduce the acoustic energy and can reduce the maximum range of the ultrasonic sensor.

The range of ultrasonic signals is also influenced by the relative humidity and temperature of the ambient air. Generally speaking, the sensing range decreases with increasing temperature and increasing humidity. This reduction is not linear and differs from sensor to sensor.

Ultrasonic sensors with adjustable sound beams allow customization of the sensing threshold. The sensing range can be adjusted to suit the object being detected via programming software or a Teach-In function. Pepperl+Fuchs’ ultrasonic sensors are programmed using the ULTRA3000, SONPROG, PACTware (IO-LINK), or ULTRA-PROG-IR software.

They enable precise control of the overall acoustic beam width. This means that the beam can be reduced in both length (axial sound beam) and width (lateral sound beam). Lateral and axial sound beam width can also be adjusted independently. This allows disruptive or reflective objects within the sensing range to be suppressed. Reducing the sound beam size allows disruptive objects or attachments on machines or in tanks to be suppressed.