US3761805A
Expired / Lapsed
US
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Methods of and systems for measuring capacitance using a constant current charging technique
Assignee: AT&T Inc
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Filing: 1971-06-24
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Granted: 1973-09-25
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Expires: 1991-06-24
Abstract
Abstract In a constant current charging tenchique for measuring capacitance, a constant current is supplied to a capacitance to be measured and a voltage ramp is produced. Two voltage-level detectors sense the ramp. At a low level on the ramp, a first of the detectors triggers a time-interval meter which begins to count pulses from an oscillator. A second of the detectors stops the counting process when the voltage ramp reaches an upper level. The time measured by the meter is proportional to the value of the capacitance and can be used to calculate the actual value.
Inventors
- 👤 G Dornberger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:12
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/26; G01R27/2605
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
114 words
A method of measuring a capacitance value which comprises the steps of: charging a capacitance with a constant current to generate a voltage ramp by the capacitance during the charging of the capacitaNce; designating a first voltage value selected to occur while the ramp is rising linearly wherein the first value has a magnitude greater than the magnitude of any oscillations induced in the voltage ramp due to initially charging the capacitance; designating a second voltage value selected to occur subsequent to the first value and while the ramp is rising linearly, and measuring the time required for the voltage ramp to rise linearly from the first voltage value to the second voltage value.
Claim 2
Independent Claim
114 words
A method of measuring a capacitance value which comprises the steps of: charging a capacitance with a constant current to generate a voltage ramp by the capacitance during the charging of the capacitaNce; designating a first voltage value selected to occur while the ramp is rising linearly wherein the first value has a magnitude greater than the magnitude of any oscillations induced in the voltage ramp due to initially charging the capacitance; designating a second voltage value selected to occur subsequent to the first value and while the ramp is rising linearly, and measuring the time required for the voltage ramp to rise linearly from the first voltage value to the second voltage value.
Claim 3
Independent Claim
128 words
A method of measuring a capacitance value existing between two insulated conductors of a plurality of conductors which are stranded together to form a core of a communications cable, the method comprising the steps of: applying a constant current to the conductors to charge a capacitance therebetween to thereby develop a voltage rise; detecting when the voltage rise reaches a first predetermined value selected to occur subsequent to random oscillations resulting upon initial application of the current and selected to occur while the voltage rise is substantially linear; detecting when the voltage rises to a second predetermined value selected to occur while the voltage rise is substantially linear, and measuring the time required for the voltage to rise from the first predetermined value to the second predetermined value.
Claim 4
Independent Claim
128 words
A method of measuring a capacitance value existing between two insulated conductors of a plurality of conductors which are stranded together to form a core of a communications cable, the method comprising the steps of: applying a constant current to the conductors to charge a capacitance therebetween to thereby develop a voltage rise; detecting when the voltage rise reaches a first predetermined value selected to occur subsequent to random oscillations resulting upon initial application of the current and selected to occur while the voltage rise is substantially linear; detecting when the voltage rises to a second predetermined value selected to occur while the voltage rise is substantially linear, and measuring the time required for the voltage to rise from the first predetermined value to the second predetermined value.
Claim 5
Independent Claim
158 words
A system for measuring a capacitance value existing between two insulated conductors of a plurality of conductors which are stranded together to form a core of a communications cable, the system comprising: means for applying a constant current to the conductor to develop a voltage rise in the system due to a capacitance between the conductors; first means coupled to the conductors for detecting when the voltage rise reaches a first predetermined value selected to occur subsequent to random oscillations resulting in the system upon initially applying the current and while the voltage rise is substantially linear; second means coupled to the conductors for detecting when the voltage rise reaches a second predetermined value selected to occur subsequent to the first value and while the voltage rise is still linear, and means coupled to the first and second detecting means for measuring the time required for the voltage to rise from the first value to the second value.
Claim 6
Independent Claim
158 words
A system for measuring a capacitance value existing between two insulated conductors of a plurality of conductors which are stranded together to form a core of a communications cable, the system comprising: means for applying a constant current to the conductor to develop a voltage rise in the system due to a capacitance between the conductors; first means coupled to the conductors for detecting when the voltage rise reaches a first predetermined value selected to occur subsequent to random oscillations resulting in the system upon initially applying the current and while the voltage rise is substantially linear; second means coupled to the conductors for detecting when the voltage rise reaches a second predetermined value selected to occur subsequent to the first value and while the voltage rise is still linear, and means coupled to the first and second detecting means for measuring the time required for the voltage to rise from the first value to the second value.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-24 | 1977-03-26 | 1977-09-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-24 | 1981-03-26 | 1981-09-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-24 | 1985-03-26 | 1985-09-25 | $7700.00 | Window Closed / Lapsed |