Method and apparatus for sensing liquid level using baseline characteristic
First Claim
1. A method for determining a level of a liquid in a tank, comprising:
- providing a tank in which a liquid level is variable;
measuring a baseline characteristic of a probe circuit including a probe associated with the tank while the probe is out of contact with the liquid in the tank;
starting a filling of the tank from a level at which the probe is out of contact with the liquid;
measuring a first characteristic of the probe circuit after measuring the baseline characteristic and during filling of the tank;
determining the liquid level in the tank corresponding to about a time that the first characteristic is measured based on the first characteristic and the baseline characteristic;
wherein if the step of determining determines that the liquid is out of contact with the probe, the method further comprises;
assigning an updated value as the baseline characteristic based on a characteristic measured during filling of the tank;
measuring a second characteristic of the probe circuit after measuring the first characteristic and during filling of the tank; and
determining the liquid level in the tank corresponding to about a time that the second characteristic is measured based on the second characteristic and the updated baseline characteristic.
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Accused Products
Abstract
A liquid level sensing arrangement using a probe uses a baseline probe circuit characteristic, e.g., a circuit resistance or voltage, that is measured when the probe is out of contact with the liquid in the tank. The baseline characteristic may be used to determine a liquid level in the tank, e.g., a determination whether the liquid level is below or at/above the probe. In one embodiment, the baseline characteristic may be compared to a circuit characteristic that is measured as the tank is being filled. A difference between the baseline characteristic and the other circuit characteristic may be used to determine whether or not the probe is in contact with the liquid.
143 Citations
28 Claims
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1. A method for determining a level of a liquid in a tank, comprising:
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providing a tank in which a liquid level is variable; measuring a baseline characteristic of a probe circuit including a probe associated with the tank while the probe is out of contact with the liquid in the tank; starting a filling of the tank from a level at which the probe is out of contact with the liquid; measuring a first characteristic of the probe circuit after measuring the baseline characteristic and during filling of the tank; determining the liquid level in the tank corresponding to about a time that the first characteristic is measured based on the first characteristic and the baseline characteristic; wherein if the step of determining determines that the liquid is out of contact with the probe, the method further comprises; assigning an updated value as the baseline characteristic based on a characteristic measured during filling of the tank; measuring a second characteristic of the probe circuit after measuring the first characteristic and during filling of the tank; and determining the liquid level in the tank corresponding to about a time that the second characteristic is measured based on the second characteristic and the updated baseline characteristic. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A liquid level determining system comprising:
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a probe circuit including a conductive probe constructed and arranged to contact a liquid in a tank in which a liquid level is variable; and a controller adapted to measure a baseline characteristic of the probe circuit while the conductive probe is out of contact with the liquid in the tank, measure a first characteristic of the probe circuit after measuring the baseline characteristic and during filling of the tank, and determine the liquid level in the tank corresponding to about a time that the first characteristic is measured based on the first characteristic and the baseline characteristic; wherein the controller is adapted to assign an undated value as the baseline characteristic based on a characteristic measured during filling of the tank if the liquid is determined to be out of contact with the conductive probe at about the time that the first characteristic is measured; and wherein the controller is adapted to measure a second characteristic of the probe circuit after measuring the first characteristic and during filling of the tank, and adapted to determine a liquid level corresponding to about a time that the second characteristic is measured based on the second characteristic and the updated baseline characteristic. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A method for determining a level of a liquid in a tank, comprising:
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providing a tank in which a liquid level is variable; measuring a baseline characteristic of a probe circuit including a conductive probe associated with the tank while the conductive probe is out of contact with the liquid in the tank; starting a filling of the tank from a level at which the probe is out of contact with the liquid; measuring a first characteristic of the probe circuit after measuring the baseline characteristic and during filling of the tank; determining the liquid level in the tank corresponding to about a time that the first characteristic is measured based on the first characteristic and the baseline characteristic; wherein if the step of determining determines that the liquid is out of contact with the conductive probe, the method further comprises; assigning an undated value as the baseline characteristic based on a characteristic measured during filling of the tank; measuring a second characteristic of the probe circuit after measuring the first characteristic and during filling of the tank; and determining a liquid level corresponding to about a time that the second characteristic is measured based on the second characteristic and the baseline characteristic.
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Specification