ABSTRACT
Level is deŸned as the Ÿlling height of a liquid or bulk material, for example, in a tank or reservoir. Generally, the position of the surface is measured relative to a reference plane, usually the tank bottom. If the product’s surface is not žat (e.g., with foam, waves, turbulences, or with coarse-grained bulk material), level usually is deŸned as the average height of a bounded area.
