Accurate - used with the Vessel Systems Monitor VSM 422 PN 1800?can be precisely calibrated for each tank*. Reliable - SSI Technologies, Inc. Fluid-Trac? is non-contacting eliminating any mechanical moving parts that can wear and cause intermittent or complete signal loss. Digital filtering - Eliminates errors due to liquids sloshing in mobile tanks Limitations and considerations for mounting the ultrasonic tank senders: Senders are calibrated to the VSM 422 and will not function with other monitors. Senders must be mounted 4" or greater distance from a tank side or baffle. Tank floor must not be sloped. Tanks must not be deeper than 24". Sender must be mounted perpendicular to the surface of the liquid. The sender negative connection should be connected as directly as possible to the main negative bus.