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US 6,634,229 B1Granted
Resistive fluid level sensing and control system
AssigneeIllinois Tool Works Inc.
InventorsGhaffar Kazkaz, Richard C. Francke, Bradley S. Beiermann
Life of this patent
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Abstract
A fluid level sensing systems including a resistive element having an upper end portion disposed in an upper portion of a container and a lower end portion disposed in a lower portion of the container. The resistance of the resistive element varies between the upper and the lower portions of the container. An at least partially conductive strip having substantially the same length as the resistive element is disposed in the container generally parallel thereto and at approximately the same level in the container as the resistive element. An input signal source is coupled to the resistive element by a series resistor.
Claims30
A fluid level sensing system comprising:
- a container having lower and upper portions;
- a resistive element disposed in the container, the resistive element having an upper end portion disposed in the upper portion of the container and a lower end portion disposed in the lower portion of the container,
- a resistance of the resistive element increases from the upper portion of the container toward the lower portion of the container,
- the resistive element is a semi-conductive film strip deposited onto a non-conductive substrate, the semi-conductive film strip comprises a plurality of discrete strip portions each having a corresponding width dimension such that an output signal across the film strip varies substantially linearly with changing fluid level in the container,
- a plurality of electrodes disposed thereon in spaced apart relation between the upper and lower end portions of the resistive element, each of the plurality of electrodes is coupled to a corresponding discrete portion of the resistive element;
- an at least partially conductive strip disposed in the container generally parallel to the resistive element, the at least partially conductive strip and the resistive element having approximately the same length and positioned at approximately the same level as the resistive element in the container,
- a series resistor having a first end portion coupled to the upper end portion of the resistive element;
- an input signal source coupled to a second end portion of the series resistor.
5 more elements
A fluid level sensing resistive element comprising:
- a non-conductive substrate having a first end portion and an opposite second end portion;
- an electrically insulated semi-conductive film strip deposited onto the non-conductive substrate, the semi-conductive film strip having a first end portion disposed toward the first end portion of the non-conductive substrate and a second end portion disposed toward the second end portion of the non-conductive substrate,
- the semi-conductive film strip having a plurality of discrete strip portions each having a corresponding width dimension, the width dimensions of discrete strip portions toward the first end portion of the non-conductive substrate are wider than the width dimensions of discrete strip portions toward the second end portion of the non-conductive substrate;
- a plurality of electrodes disposed in spaced apart relation on the non-conductive substrate, each of the plurality of electrodes is coupled to a corresponding discrete strip portion.
1 more element
A fluid level sensing resistive element comprising:
- a non-conductive substrate having a first end portion and an opposite second end portion;
- an electrically insulated semi-conductive film strip deposited onto the non-conductive substrate, the semi-conductive film strip having a first end portion disposed toward the first end portion of the non-conductive substrate and a second end portion disposed toward the second end portion of the non-conductive substrate,
- the semi-conductive film strip having a width dimension with a continuously narrowing taper between the first and second end portions thereof, the first end portion of the semi-conductive film strip having a wider width dimension than the second end portion thereof.
A fluid level sensing system comprising:
- a fluid container having a side wall with upper and lower portions,
- a resistive element disposed in the container, the resistive element having an upper end portion disposed in the upper portion of the container and a lower end portion disposed in the lower portion of the container,
- the resistive element is a semi-conductive film strip deposited onto a non-conductive substrate, the film strip comprises a plurality of discrete strip portions each having a corresponding width dimension, a plurality of conductive film portions deposited onto the non-conductive substrate, each conductive film portion is coupled to a corresponding discrete strip portion,
- a resistance of the resistive element increases toward the lower end portion thereof and decreases toward the upper end portion thereof,
- an at least partially conductive strip disposed in the container generally parallel to the resistive element, the at least partially conductive strip and the resistive element having at least approximately the same length and positioned at approximately the same level as the resistive element in the container,
- an alternating input signal circuit coupled to the upper end portion of the resistive element;
- a converter circuit having an input and an output, the input of the converter circuit coupled to the at least partially conductive strip,
- a comparator circuit having a signal input, the output of the converter circuit coupled to the signal input of the comparator circuit.
5 more elements
Dependencies are inferred from the claim text.