Switch level control for tank ullage determining system

Abstract

A liquid level sensor for a tank includes coaxial inner and outer tubes having lower ends extending into the tank and upper ends projecting from the tank, with the upper end of the inner tube projecting from the outer tube and disposed a known distance from the top of the tank. A switch assembly includes a switch disposed in the inner tube and operable in response to proximity to a switch actuator which is carried by a float encircling the outer tube and movable therealong with the liquid level, the switch being connected across a pair of electrical conductors extending from the upper end of the inner tube. An indicator strip extends lengthwise of the conductors and is held thereagainst by a transparent sleeve, the strip having indicia indicating distance to the switch. Plastic cable ties extend through openings in the inner tube and snugly hold the switch assembly against the inner tube to permit manual axial movement of the switch assembly while preventing inadvertent movement thereof. The upper end of the inner tube is cut away to permit observation of alignment of the indicia with a reference mark on the inner tube. Plural tubes and switch assemblies with appropriate color coding may be provided.