Capacitive fluid level sensor
First Claim
1. A device for sensing the liquid level in the container comprising:
- first and second elongated tubes in said container arranged one inside the other in a concentric, spaced relationship to reduce the effect of liquid sloshing in the container;
a continuous conductive surface on one of the elongated tubes to form one plate of a capacitor;
a plurality of separate, electrically-conductive surfaces arranged in a longitudinally-spaced relationship along the surface of the other of the elongated tubes in cooperative spaced relationship to said continuous conductive surface to form a plurality of individual capacitors that progressively increase in number from one end to the other of the tubes;
said separate electrically-conductive surfaces being physically and electrically isolated from one another;
each said separate electrically-conductive surface occupying a discrete longitudinal length of said other tube and with no part of one separate electrically-conductive surface extending beyond its discrete longitudinal length of said other tube into a discrete longitudinal length of said other tube occupied by an adjacent separate electrically-conductive surface;
means for utilizing the plurality of capacitors to determine the liquid level in the container; and
means for individually electrically connecting said continuous conductive surface and each of said separate electrically-conductive surfaces with said means for utilizing.
1 Assignment
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Accused Products
Abstract
A device that determines liquid level or volume by means of charging a plurality of capacitors in sequence. Each capacitor is charged for a fixed time interval. The voltage level obtained is a function of the liquid level and is compared with a known voltage to obtain an output signal that can be used to represent liquid depth. The capacitors are formed by two concentric tubes, one inside the other in a spaced relationship. The tubes reduce the effect of sloshing in the tank, resulting in a more stable reading. To measure volume or level in an irregular shaped tank, the capacitors can be arranged in a non-linear manner. The device has no moving parts to wear out and thus results in higher reliability and longer life.
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Citations
10 Claims
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1. A device for sensing the liquid level in the container comprising:
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first and second elongated tubes in said container arranged one inside the other in a concentric, spaced relationship to reduce the effect of liquid sloshing in the container; a continuous conductive surface on one of the elongated tubes to form one plate of a capacitor; a plurality of separate, electrically-conductive surfaces arranged in a longitudinally-spaced relationship along the surface of the other of the elongated tubes in cooperative spaced relationship to said continuous conductive surface to form a plurality of individual capacitors that progressively increase in number from one end to the other of the tubes; said separate electrically-conductive surfaces being physically and electrically isolated from one another; each said separate electrically-conductive surface occupying a discrete longitudinal length of said other tube and with no part of one separate electrically-conductive surface extending beyond its discrete longitudinal length of said other tube into a discrete longitudinal length of said other tube occupied by an adjacent separate electrically-conductive surface; means for utilizing the plurality of capacitors to determine the liquid level in the container; and
means for individually electrically connecting said continuous conductive surface and each of said separate electrically-conductive surfaces with said means for utilizing. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A fluid level sensor for a container comprising:
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first and second elongated tubes in said container arranged one inside the other in a concentric, spaced relationship to reduce the effects of fluid sloshing in the container; a continuous conductive surface formed in the inside of the outer tube and the outside of the inner tube to form an elongated capacitor; means for charging the elongated capacitor at consecutive intervals for a fixed amount of time to achieve a voltage level that varies with the dielectric constant and the depth of the liquid in which the elongated capacitor is immersed; a plurality of reference voltage levels each of which represents a predetermined liquid level in the container; means for sequentially comparing each reference voltage level with the capacitor voltage level obtained at each consecutive interval to generate an output signal representing a change in the liquid level in the containers; a counter coupled to the output of the comparing means for counting each output signal representing a change in liquid levels; and decoding means coupled to the counter for converting the count to signals for driving the visual display.
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9. A device for sensing the liquid level in the container comprising:
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first and second elongated tubes in said container arranged one inside the other in a concentric, spaced relationship to reduce the effect of liquid sloshing in the container; a continuous conductive surface on one of the elongated tubes to form one plate of a capacitor; a plurality of separate, electrically-conductive surfaces arranged in a spaced relationship on the surface of the other of the elongated tubes to form a plurality of individual capacitors; at least a third elongated insulated surface concentric with and spaced from the first and second elongated tubes; an electrically conductive surface on the third elongated insulated surface connected in electrical parallel with a selected one of the conductor surfaces on the first and second elongated tubes to increase the capacitance and the sensitivity of the device; and means for utilizing the plurality of capacitors to determine the liquid level in the container. - View Dependent Claims (10)
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Specification