Abstract: A system for measuring the level of liquid stored in deep tanks or vessels that allows the use of a lightweight, relatively non-toxic, non-corrosive gauge fluid of normal column height is disclosed. The system discloses a diaphragm manometer that alters a greater pressure from the tank liquid into a lesser pressure from the gauge fluid permitting such gauge fluid to be lightweight and making it unnecessary to use high density fluids which are usually toxic, contaminating and have other undesirable handling characteristics. The device can be used for open tanks, or, with adaptations, for sealed tanks. For open tanks, the device provides two sealed chambers having two opposing diaphragms. For sealed tanks, pressure neutralizing elements are added with one device providing three sealed chambers and two diaphragms with neutralizing connectors, and another providing three sealed chambers and three diaphragms.

Abstract: A system for measuring the water level, within a predetermined range, at the bottom of a tank containing gasoline. A first air bell is adapted to be inserted into said tank and has an opening in the lower part thereof to define a first interface. A second air bell is disposed interiorly of the first air bell and has an opening in the lower part thereof to define a second interface which is lower than the first interface. The upper ends of the air bells are in communication, respectively, with opposite legs of a manometer so as to produce a displacement of manometer liquid as a function of the difference of hydrostatic pressure between said interfaces whereby said displacement is a function of the water level therebetween, there being minimum displacement when the water level is at said second interface and maximum displacement when the water level is at said first interface.