Importance

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Abstract

Two embodiments of an analog liquid level sensor are provided for measuring the level of a liquid in a container having a volume/depth relationship wherein each sensor has a resistance-to-float-displacement profile matched to the volume/depth relationship of the container. Each sensor includes a dielectric coated metal bar which acts as a heat sink and a ground plane. A pair of electrically spaced terminals and a printed circuit including a thick film resistor pattern and a metallization pattern having metallized graduations are formed on the metal bar for reduced electrical noise characteristics and improved hysteresis. The resistance of the resistor pattern is electrically coupled between the terminals and has a resistance which varies at different positions between the terminals. The metallization pattern is formed on the resistor pattern which, in turn, is formed on opposite sides of the dielectric coated metal bar. A float assembly including a buoyant housing and a contact assembly is connected to the dielectric coated metal bar to reciprocate in a generally vertical direction in response to the level of the liquid in the container. The contact assembly is connected to the buoyant housing in a fixed vertical relationship thereto for making electrical connection with the metallization pattern and for changing the effective resistance of the resistor pattern between the terminals. The contact assembly includes a pair of spring-loaded wiper contacts for making electrical connection with the graduations of the metallization pattern on opposite sides of the metal bar. The terminals provide an electrical signal which is a function of the vertical position of the wiper contacts along the metal bar.

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First Claim