Used to detect the level of settled sediment or solid materials in a tank containing liquids, the VR-21 SED and VR-41 SED function by vibrating until the settled solid material reach the level of the rod. These vibrating rods can be wired to an alarm panel or horn to alert when sediment has reached the probe's level. The standard model VR-21 SED has a 7.37" insertion length and is recommended for use on the tank wall. The VR-41 SED model is a rigid extended vibrating rode for top mounting applications. It is custom made to fit the needs of the application with extensions from 13 inches to 13 feet long.