Two measurement principles are recommended for the continuous level measurement of bulk solids: ultrasonic (Prosonic) and guided microimpulses (Levelflex).

For a long time ultrasonic was the only non-contact continuous measurement beside radioactive measurements. It is still recommended for hard and large-grained material and for dust-free applications.

For dusty powders, fine powders with a reflecting surface, for narrow silos or for silos with many cross-struts "guided microimpulses" is a modern measurement principal that is optimized for these applications. It measures independent of physical properties such as moisture content, particle size, density and electrical properties. The only condition is a minimum dielectric constant. It is a safe, reliable and flexible solution for most cases of standard and heavy-duty applications.