Ultrasonic sensors can detect solids, liquids, and powders. The surface properties of the object are critical for the sensor’s echo evaluation. Level, smooth surfaces at right angles to the beam produce ideal reflections. The angular deviation of the measurement plate must not exceed 3° to ensure reliable detection.
Material properties such as transparency, color, or surface treatment (polished or matte) have no effect on detection reliability. Rough surfaces reflect the acoustic energy in multiple directions. This decreases the overall detection range. Conversely, rough surfaces allow greater angular deviation due to the predominantly diffuse reflection of the ultrasound signal.
This characteristic can be used to detect filling levels or piles of coarse-grained materials with an angular deviation of up to 45° (at a reduced range).
The following objects can be detected particularly well:
- All smooth and solid objects aligned perpendicular to the beam angle
- All solid objects with a surface roughness that cause diffuse reflections and that are randomly aligned
- Surfaces of liquids at an angle <3° from the beam axis
The following materials are poorly detected:
- Materials that absorb ultrasonic signals, such as felt, cotton, rough textiles, or foam
- Materials with temperatures of more than 100° C
In these cases, a thru-beam sensor may be required for such materials.