Fluid level sensor and controller
AssigneeRaytheon Company
InventorsJoseph R. Adamski, Donald A. Coates
Life of this patent
Estimating the term…
Abstract
A fluid level sensor for determining the amount of liquid in a container. Thin metal plates are placed parallely adjacent each other to form a capacitor cell coated with a non-hygroscopic film. The plates are mounted on the walls of the container containing fluid. As the fluid covers more surface area of the capacitor plates, the dielectric properties of the fluid increase the capacitance of the cell proportionally. The plates are connected to an oscillator whose output frequency varies with the change in container fluid levels. By monitoring these frequency changes, the container fluid levels of the fluid in the container can be controlled.
Claims18
An apparatus for sensing the level of liquid in a container comprising:
- first and second parallel metal plates having opposingly facing flat surfaces and providing a capacitance;
- means for supporting said plates inside said container;
- insulating spacing means, attached to said first and second plates for maintaining a constant spacing between said first and second plates;
- and
- means electrically coupled to said plates for detecting said capacitance and for generating in response to said capacitance a signal indicating the level of liquid in said container;
- wherein said first and second parallel metal plates are shaped to support said detecting and signal generating means.
A washing machine comprising:
- an outer tub;
- an inner tub disposed within said outer tub;
- an agitator positioned in said inner tub;
- means for driving said agitator;
- and
- means for sensing the level of liquid in said outer tub, said sensing means comprising:
- (a) first and second parallel metal plates having opposingly facing flat surfaces;
- (b means for supporting said plates inside said outer tub;
- (c) insulating spacing means, attached to said first and second plates, for maintaining a constant spacing between said first and second plates;
- and
- (d) means attached to a portion of said first and second plates for generating a signal indicating the level of liquid in said tub.
A method of sensing the level of liquid in a washing machine comprising the steps of:
- positioning first and second parallel metal plates having opposingly facing flat surfaces in a substantially vertical position within the liquid within said machine;
- coating said plates with a non-corrosive material;
- maintaining a constant spacing by an insulating spacer between said first and second plates of less than approximately 0.5 inches;
- sensing the capacitance between the first and second plates;
- generating a signal having a frequency proportional to the level of liquid in said washing machine in response to said capacitance;
- and
- attaching a circuit board to said metal plates, said circuit board containing circuitry that senses the capacitance between said first and second plates and generates said signal.
Dependencies are inferred from the claim text.