US5554937A
Expired / Lapsed
US
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Apparatus and method for sensing material level by capacitance measurement
Assignee: Penberthy Inc
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Filing: 1995-05-15
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Granted: 1996-09-10
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Expires: 2015-05-15
Abstract
Abstract A highly accurate system to measure the level of material in a vessel. A probe is provided in the vessel. The vessel and the probe are at different potentials so as to create a capacitance therebetween. The air and materials in the vessel act as dielectrics. As the material level varies, so does the capacitance. This capacitance is subjected to a charge-discharge-charge cycle yielding integrated net neutral charge. The duration of the cycle is compared to a reference time to determine capacitance, which is proportional to the level of material in the vessel.
Inventors
- 👤 Gary G. Sanders
- 👤 Brian J. Goodwin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 00:35
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/26; G01F; G01F23/00; G01F23/22; G01F23/26; G01F23/263; G01F23/266; G01R27/2605
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
112 words
A device for monitoring the level of a material in a container, comprising: probe means for developing a capacitance that varies with the level of material in the container; charging means for subjecting the capacitance to a charge-discharge-charge cycle, wherein the capacitance is linearly charged to a first predetermined voltage, then linearly charged to a second predetermined voltage that is opposite in polarity from the first predetermined voltage, and then linearly charged to a reference voltage that is intermediate the first and second predetermined voltages; and output means for generating an output signal that varies in accordance with the duration of the charge-discharge-charge cycle, said duration being directly proportional to said capacitance.
Claim 2
Independent Claim
112 words
A device for monitoring the level of a material in a container, comprising: probe means for developing a capacitance that varies with the level of material in the container; charging means for subjecting the capacitance to a charge-discharge-charge cycle, wherein the capacitance is linearly charged to a first predetermined voltage, then linearly charged to a second predetermined voltage that is opposite in polarity from the first predetermined voltage, and then linearly charged to a reference voltage that is intermediate the first and second predetermined voltages; and output means for generating an output signal that varies in accordance with the duration of the charge-discharge-charge cycle, said duration being directly proportional to said capacitance.
Claim 3
Dependent Claim
54 words
The device of claim 1 further comprising means for generating a clock signal having a period that defines a reference time, wherein the charge-discharge-charge cycle is initiated at the beginning of the reference time, and wherein the output signal varies in accordance with the duration of the charge-discharge-charge cycle relative to the reference time.
Claim 4
Dependent Claim
28 words
The device of claim 2 wherein, after the charge-discharge-charge cycle is complete, the charging means maintains the capacitance at the reference voltage until the reference time has elapsed.
Claim 5
Dependent Claim
18 words
The device of claim 1 wherein the integrated net charge of the charge-discharge-charge cycle is equal to zero.
Claim 6
Dependent Claim
20 words
The device of claim 4 wherein the first and second predetermined voltages are equal in magnitude and opposite in polarity.
Claim 7
Dependent Claim
63 words
The device of claim 1 wherein the charging means includes a first and second constant current sources having opposite polarities, wherein the changing means initially couples the capacitance to the first current source to linearly charge the capacitance to the first predetermined voltage, and then couples the capacitance to the second current source to linearly charge the capacitance to the second predetermined voltage.
Claim 8
Dependent Claim
37 words
The device of claim 1 wherein at the completion of the charge-discharge-charge cycle, the charging means holds the capacitance at the reference voltage for an amount of time sufficient to substantially reduce the effects of dielectric absorption.
Claim 9
Dependent Claim
37 words
The device of claim 1 wherein the charging means periodically repeats the charge-discharge-charge cycle, and, at the end of each charge-discharge-charge cycle, maintains the capacitance at the reference voltage until the beginning of the next charge-discharge-charge cycle.
Claim 10
Independent Claim
114 words
A method for measuring the level of a material in a vessel, comprising the steps of: developing a capacitance between a probe and the vessel, said capacitance varying with the level of the material in the container; subjecting the capacitance to a charge-discharge-charge cycle, wherein the capacitance is linearly charged to a first predetermined voltage, then linearly charged to a second predetermined voltage that is opposite in polarity from the first predetermined voltage, and then linearly charged to a reference voltage that is intermediate the first and second predetermined voltages; and generating an output signal that varies in accordance with the duration of the charge-discharge-charge cycle, said duration being directly proportional to said capacitance.
Claim 11
Independent Claim
114 words
A method for measuring the level of a material in a vessel, comprising the steps of: developing a capacitance between a probe and the vessel, said capacitance varying with the level of the material in the container; subjecting the capacitance to a charge-discharge-charge cycle, wherein the capacitance is linearly charged to a first predetermined voltage, then linearly charged to a second predetermined voltage that is opposite in polarity from the first predetermined voltage, and then linearly charged to a reference voltage that is intermediate the first and second predetermined voltages; and generating an output signal that varies in accordance with the duration of the charge-discharge-charge cycle, said duration being directly proportional to said capacitance.
Claim 12
Dependent Claim
55 words
The method of claim 9 further comprising the step of generating a clock signal having a period that defines a reference time, wherein the charge-discharge-charge cycle is initiated at the beginning of the reference time, and wherein the output signal varies in accordance with the duration of the charge-discharge-charge cycle relative to the reference time.
Claim 13
Dependent Claim
29 words
The method of claim 9 further comprising the step of after the charge-discharge-charge cycle is complete, maintaining the capacitance at the reference voltage until the reference time has elapsed.
Claim 14
Dependent Claim
18 words
The method of claim 9 wherein the integrated net charge of the charge-discharge-charge cycle is equal to zero.
Claim 15
Dependent Claim
20 words
The method of claim 12 wherein the first and second predetermined voltages are equal in magnitude and opposite in polarity.
Claim 16
Dependent Claim
65 words
The method of claim 9 wherein the step of charging the capacitance to the first predetermined voltage is accomplished by coupling the capacitance to a first constant current source, and the step of linearly charging the capacitance to the second predetermined voltage is accomplished by coupling the capacitance to a second constant current source, wherein said first and second constant current sources have opposite polarity.
Claim 17
Dependent Claim
38 words
The method of claim 9 further comprising the step of, at the completion of the charge-discharge-charge cycle, holding the capacitance at the reference voltage for an amount of time sufficient to substantially reduce the effects of dielectric absorption.
Claim 18
Dependent Claim
38 words
The method of claim 9 further comprising the step of periodically repeating the charge-discharge-charge cycle, and, at the end of each charge-discharge-charge cycle, maintaining the capacitance at the reference voltage until the beginning of the next charge-discharge-charge cycle.
Claim 19
Dependent Claim
26 words
The method of claim 9 further comprising the step of using the output signal to drive a display indicating the level of material in the vessel.
References Cited (Backward Citations)
US3778708A
Cited
US3993947A
Cited
US4146834A
Cited
US4146834B1
Cited
US3993947B1
Cited
US4499766A
Cited
US4558274A
Cited
US4939519A
Cited
US5045797A
Cited
US5278513A
Cited
US4968946A
Cited
US5014011A
Cited
US4942401A
Cited
US5294889A
Cited
US5446444A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-09-10 | 2000-03-11 | 2000-09-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-09-10 | 2004-03-11 | 2004-09-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-09-10 | 2008-03-11 | 2008-09-10 | $7700.00 | Window Closed / Lapsed |