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.

Abstract: A hand-held interface couples fill level detection switch terminals on a tank barge with current source terminals of a dockside facility. The interface includes a dockside connector adapted to be connected to the dockside terminals and a barge connector adapted to be connected to the barge terminals and test circuits for respectively testing the lading level detection switches. Each test circuit includes a battery connected in series with the light source of an optocoupler across a pair of terminals of the barge connector. Also connected across the battery are the light-sensitive switching element of the optocoupler, the coil of a normally-open relay and an indicator LED, the contacts of the relay being connected across a pair of terminals of the dockside connector. When the interface connectors are respectively connected to the barge and dockside terminals, the level detection switch under test completes the circuit across the battery through the optocoupler light source so that the optocoupler is energized.

Abstract: A universal read head for a tank-level float gauge is adapted for use with any of certain different types of gauge rods which may be connected to a float element in the tank, including rods having an optical code thereon including a plurality of alternating reflecting and non-reflecting stripes arranged between magnetic end portions, and a rod with one or more magnets disposed adjacent to each end thereof and longitudinally spaced magnets intermediate the ends. The sensing head includes an LED light source for illuminating the rod and two phototransistors coupled in quadrature relationship for detecting the illuminated optical code patterns, and two magnetic reed switches for sensing the proximity of magnets on the gauge rod. The sensors are coupled to a microprocessor for interpreting the electrical signals generated by the sensors to identify the type of gauge rod being used and to provide an indication of the position of the gauge rod relative to the sensors.

Abstract: An optical tank-level gauge includes an elongated gauge rod magnetically coupled at its lower end to a float for rising and falling with the liquid level. The outer surface of the rod is provided along most of its length with alternating reflecting and non-reflecting circumferential stripes of equal height, the rod having non-reflecting zones at its opposite ends. An optical read head is fixed on the tank and includes LEDs for illuminating the rod and four optical sensors spaced apart longitudinally along the rod and arranged into quadrature pairs relative to the stripes, so that each pair reads a longitudinal extent of the rod substantially equal to the height of one stripe. Each of the non-reflecting end zones has a height such that, in either the full or empty condition, the fields of view of all four optical sensors will be completely within one or the other of the end zones.

Abstract: The gauge has an outer tube sealed at its lower end and adapted for attachment to the top wall of the tank, and an inner tube axially movable within the outer tube. A float encircles the outer tube and moves freely therealong. First and second magnets respectively attached to the float and to the lower end of the inner tube provide magnetic coupling therebetween so that a rising liquid causes the inner tube to rise with the float. Magnets within the inner tube operate a switch to signal when the first and second magnets are in position for magnetic coupling therebetween. Another magnet is fixed by a set screw to the outside of the inner tube in position for operating the switch when the tank is substantially full. Retaining clips are also disclosed for holding the latter magnet in place.