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: Sensors for mounting in fluid chambers respond electrically to low pressures in the fluid, while resisting damage or leakage at high pressures. A flexible diaphragm, mounted at one end of a housing, is sandwiched between first and second annuli, leaving a center portion free to move in response to fluid pressure changes. The diaphragm moves a cylinder, which reciprocates in the second annulus against an adjustable spring bias. Travel of the cylinder away from the fluid is limited by a stop. Once the stop is reached, increased pressure on the diaphragm forces it against a fixed wall composed of a face of the second annulus and a face of the cylinder. The forces on the diaphragm are then all compressive. This enables the use of an easily flexed diaphragm for low pressure sensitivity, while resisting damage from high pressures. The moving cylinder is used to move a magnet that actuates a Hall effect switch, a Hall effect analog output transducer, or a reed switch.

Abstract: A target flow meter has a target with a broad face attached to the free end of an elastic stalk. The stalk has at least a portion with an oblong cross section. A fixed end of the stalk is attached to a rigid support secured in the system to be measured with the broad face disposed transverse to the fluid flow. Strain gauges are affixed to the longer sides of the oblong portion. A temperature sensor may also be affixed there. The strain gauges are immersed in the fluid to be measured. Wires to the gauges and sensor pass through a fixed seal to the outside. They may be protected from the fluid by an impervious coating. By applying the strain gauges within the fluid, the system may be reduced in size, achieve greater sensitivity, and better temperature compensation.