US4477772A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Frequency compensator for a current-comparator capacitance bridge
Assignee: National Research Council Canada
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Filing: 1982-03-29
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Granted: 1984-10-16
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Expires: 2002-03-29
Abstract
Abstract A method and apparatus for rendering a high-voltage current-comparator capacitance bridge insensitive to frequency fluctuations when used for measuring inductance. A compensating current, proportional to twice the change in the current through the reference capacitor due to frequency fluctuations, is driven into the first comparator winding, through which the current from the reference capacitor passes, resulting in a current in that winding having frequency characteristics similar to those of the current passing through the second winding, which is connected to the inductance. This compensating current is derived from a reduced replica of the applied high-voltage or from the current through the reference capacitor.
Inventors
- 👤 Eddy So
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 03:58
CPC Classifications
G; G01; G01R; G01R17/00; G01R17/10; G01R27/00; G01R27/02; G01R27/26; G01R27/2611
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
93 words
In a current comparator capacitance bridge for measuring inductance wherein the bridge includes first comparator winding connected to a reference capacitor and second comparator winding for connection to the inductance, a method for rendering the bridge insensitive to frequency fluctuations comprising: deriving a compensating current proportional to twice the change in current through the reference capacitor due to the frequency fluctuations; and driving the compensating current through the first comparator windings to produce a current in the first winding having frequency characteristics similar to those of the current in the second comparator winding.
Claim 2
Dependent Claim
93 words
In a current comparator capacitance bridge for measuring inductance wherein the bridge includes first comparator winding connected to a reference capacitor and second comparator winding for connection to the inductance, a method for rendering the bridge insensitive to frequency fluctuations comprising: deriving a compensating current proportional to twice the change in current through the reference capacitor due to the frequency fluctuations; and driving the compensating current through the first comparator windings to produce a current in the first winding having frequency characteristics similar to those of the current in the second comparator winding.
Claim 3
Dependent Claim
41 words
A method as claimed in claim 1 wherein the step of deriving the compensating current includes: deriving a reduced replica of a voltage applied to the bridge; and summing currents obtained from the integral and the derivative of the derived voltage.
Claim 4
Dependent Claim
49 words
A method as claimed in claim 1 wherein the step of deriving the compensating current includes: detecting the current flowing through the reference capacitor; converting the detected current to a proportional voltage; and summing the detected current with the current obtained from the double integration of the proportional voltage.
Claim 5
Dependent Claim
116 words
In a current comparator capacitance bridge for measuring inductance wherein the bridge includes first comparator winding connected to a reference capacitor, second comparator winding for connection to the inductance, and a comparator amplifier connected to the first comparator winding for providing a reduced replica of a voltage applied to the bridge, a compensator for rendering the bridge insensitive to frequency fluctuations comprising: means for deriving a compensating current proportional to twice the current change in the reference capacitor due to frequency fluctuations; and means for driving the compensating current through the first comparator winding to produce a current in the first winding having frequency characteristics similar to those of the current through the second comparator winding.
Claim 6
Dependent Claim
116 words
In a current comparator capacitance bridge for measuring inductance wherein the bridge includes first comparator winding connected to a reference capacitor, second comparator winding for connection to the inductance, and a comparator amplifier connected to the first comparator winding for providing a reduced replica of a voltage applied to the bridge, a compensator for rendering the bridge insensitive to frequency fluctuations comprising: means for deriving a compensating current proportional to twice the current change in the reference capacitor due to frequency fluctuations; and means for driving the compensating current through the first comparator winding to produce a current in the first winding having frequency characteristics similar to those of the current through the second comparator winding.
Claim 7
Dependent Claim
26 words
A compensator as claimed in claim 1 wherein the compensating current driving means includes amplifier means and a fixed resistor connected to the first comparator winding.
Claim 8
Dependent Claim
62 words
A compensator as claimed in claim 4 or 5 wherein the compensating current deriving means includes: a series-connected integrator and resistor connected to the comparator amplifier, to provide a first current; a series-connected differentiator and resistor connected to the comparator amplifier to provide a second current; and a summing circuit for adding the first and second current to provide the compensating current.
Claim 9
Dependent Claim
87 words
A compensator as claimed in claim 4 or 5 wherein the compensating current deriving means includes: a current transformer having a primary transformer winding connected in series with the reference capacitor and the first comparator winding, and a secondary transformer winding; a current-to-voltage converter connected to the secondary transformer winding; a double integrator and resistor series connected to the converter; a summing circuit adding the current from the integrator circuit and a current derived from the converter voltage applied to a resistor, to provide the compensating current.
Claim 10
Dependent Claim
43 words
A compensator as claimed in claim 5 which further includes an inverting amplifier and a fixed resistor connected to the summing circuit, the fixed resistor being equal in magnitude to the driving means fixed resistor, for applying a current to the comparator amplifier.
References Cited (Backward Citations)
SU270882A1
Cited
SU277087A1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-10-16 | 1988-04-16 | 1988-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-10-16 | 1992-04-16 | 1992-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-10-16 | 1996-04-16 | 1996-10-16 | $7700.00 | Window Closed / Lapsed |