Abstract: A liquid level detection device (10), particularly for submersed pumps, characterized in that it comprises means (13, 14) for detecting variation of electric and/or magnetic field in relation to the variation of the level of the liquid; the means are associated with a controller (16) for switching on and off a submersed pump (12).

Abstract: Corrosion sensors and methods of their use for monitoring corrosion of a material of interest. The corrosion sensors are adapted to be placed in the environment containing the material of interest during the period when corrosion is taking place. The corrosion sensors include a power source, a visual indicator and an electrode contained on a support. Changes in the electrical resistance of the electrode facilitate a display on the visual indicator including changes in color or brightness. Some corrosion sensors have power sources activated by directing a light source or other electromagnetic radiation source at the corrosion sensor. Some corrosion sensors have visual indicators containing thermochromic or electrochromic materials that are responsive to changes in voltage drop or current flow across the visual indicator. Some corrosion sensors have tracking devices to provide tracking information about the corrosion sensor.

Abstract: A liquid level indicator apparatus provides direct readout of liquid level at high resolution using an array of vertically disposed Hall-effect magnetic switches. To overcome the limit to closer spacing of the switches imposed by their vertical dimension, they a disposed side by side horizontally and vertically by a distance less than the vertical dimension of each switch. They are mounted on a flat flexible substrate and then bent around into a hollow cylinder or prism shape. A floating magnet of annular shape surrounds the cylinder, or a magnet corresponding to the cylindrical or prismatic shape floats inside the surrounding circuit board. Several circuits are shown for displaying a liquid level readout resulting from the actuation of the switches by the magnet.

Abstract: An apparatus for indicating a fluid level in a reservoir includes a conduit for communication with a reservoir and including a sight glass. A buoyant primary float is provided within the conduit, and a stop is provided within the conduit for engaging the primary float to prevent travel of the primary float beyond an upper portion of the conduit. A buoyant secondary float in the conduit is moveable together with the primary float when the primary float is not engaged by the stop, and is moveable separately from the primary float when the primary float is engaged by the stop and a fluid level in the conduit exceeds the level of the stop such that a portion of the secondary float may travel separately within the upper portion of the conduit. The secondary float preferable includes an elongate portion that passes through an aperture in the primary float, and a buoyant upper portion that is located above the primary float and is larger than the aperture in the primary float.