US3766469A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Capacitance and loss tangent measuring apparatus
Assignee: Yokogawa Electric Corp
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Filing: 1972-06-27
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Granted: 1973-10-16
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Expires: 1992-06-27
Abstract
Abstract A measuring device for automatically, accurately and rapidly measuring the unknown capacitance and loss tangent of a sample electrical element, and capable of measurement of these parameters in power transmission elements (such as power cable, insulating oil, etc.) under conditions corresponding to those encountered in actual use. The capacitance and loss tangent measuring device provides output signals linearly related to the desired parameters from a circuit which comprises: a power source for imposing selected measuring conditions of current and voltage on the sample element to be measured, an operational amplifier circuit for providing a first voltage which is proportional to the voltage drop across said sample and which has a substantially perpendicular phase relation with said voltage drop, another circuit means for providing a second voltage which is proportional to the current flowing through said sample and which has a substantially parallel phase relation with said current, and an automatic balancing circuit, operating in accordance with the steepest descent method and responsive to the first and second voltages, for deriving by means of synchronous rectifiers and integrators two d.c. output signals from perpendicular components of an intermediate summation signal and for negatively feeding back the output signals to input multipliers receiving the first and second voltages to attain a balanced state in which the two output signals have a linear relationship with the capacitance and loss tangent of the sample element.
Inventors
- 👤 H Nakane
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 05:37
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/26; G01R27/2688; G01R27/2694; G01R27/2605
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
151 words
A measuring circuit for automatically measuring the capacitance and loss tangent of a sample element and for providing output signals linearly related to said capacitance and loss tangent, comprising: a power source for imposing selected conditions of current and voltage upon the sample element; means for providing a first voltage which is proportional to the voltage drop across the sample element and which has a substantially perpendicular phase relation with the voltage drop; means for providing second voltage which is proportional to the current flowing through the sample element and which has a substantially parallel phase relation with the current; and steepest descent balancing means responsive to the first and second voltages for deriving said two output signals, said two output signals being negatively fed back to attain a balanced state in which the two output signals have a linear relationship with the capacitance and loss tangent of the sample element.
Claim 2
Dependent Claim
151 words
A measuring circuit for automatically measuring the capacitance and loss tangent of a sample element and for providing output signals linearly related to said capacitance and loss tangent, comprising: a power source for imposing selected conditions of current and voltage upon the sample element; means for providing a first voltage which is proportional to the voltage drop across the sample element and which has a substantially perpendicular phase relation with the voltage drop; means for providing second voltage which is proportional to the current flowing through the sample element and which has a substantially parallel phase relation with the current; and steepest descent balancing means responsive to the first and second voltages for deriving said two output signals, said two output signals being negatively fed back to attain a balanced state in which the two output signals have a linear relationship with the capacitance and loss tangent of the sample element.
Claim 3
Dependent Claim
42 words
A measuring circuit as claimed in claim 1 wherein said steepest descent balancing means derives the two out-put signals from perpendicular components of an intermediate summation signal, and negatively feeds back the output signals to multipliers receiving said first and second voltages.
Claim 4
Dependent Claim
214 words
A measuring circuit as claimed in claim 1 wherein said balancing means comprises: a first multiplier for multiplying the first voltage by a first negative feedback constant; a second multiplier for multiplying the second voltage by a second negative feedback constant; an adder geneRating an intermediate summation signal from three inputs, the first input being the output voltage from the first multiplier applied through a first impedance element, the second input being the output voltage from the second multiplier applied through a second impedance element having a substantially perpendicular phase relation with the first impedance element, and the third input being the second voltage applied through a third impedance element having a substantially parallel phase relation with said first impedance element; means for separating the intermediate summation signal into two components substantially ninety degrees out of phase and for converting the two components into direct current signals respectively; and integrators for separately integrating the two direct current signals provided by said separating and converting means, the integrator outputs providing said two output signals, said signals being negatively fed back to said multipliers to provide the negative feedback constants in proportion to the output signals, whereby the balancing circuit balances with said two output signals linearly representing capacitance and loss tangent of the sample element.
Claim 5
Dependent Claim
26 words
A measuring circuit as claimed in claim 3 wherein said separating and converting means comprises synchronous rectifiers arranged to provide components ninety degrees out of phase.
Claim 6
Dependent Claim
60 words
A measuring circuit as claimed in claim 1 wherein the sample element is connected in series with the power source and with the measuring circuit, and wherein the means for providing the first voltage comprises an input capacitor receiving the voltage across the sample element, in series with an operational amplifier with a feedback resistor, in series with an inverter.
Claim 7
Dependent Claim
59 words
A measuring circuit as claimed in claim 1 wherein the sample element is connected in series with the power source and with the measuring circuit, and wherein the means for providing the second voltage comprises an operational amplifier with a feedback resistor, connected in series with said sample element, the output of said operational amplifier providing said second voltage.
Claim 8
Dependent Claim
98 words
A measuring circuit as claimed in claim 1 wherein the sample element is connected in series with the power source and with a current detecting resistor, and wherein the means for providing the first voltage comprises a differential amplifier with its inputs connected across said sample element, one input being connected to the sample element through a capacitance and the other input being connected to the junction of the sample element and current detecting resistor through a capacitance and a buffer amplifier, the output of the differential amplifier being applied to an inverter to provide the first voltage.
Claim 9
Dependent Claim
35 words
A measuring circuit as claimed in claim 7 wherein the means for providing the second voltage comprises an operational amplifier having an input resistance of kR1/(k-1) where the current detecting resistor has a value kR1.
Claim 10
Dependent Claim
26 words
A measuring circuit as claimed in claim 7 wherein said means for providing the second voltage comprises means connected to the output of the buffer amplifier.
Claim 11
Dependent Claim
114 words
A measuring circuit as claimed in claim 1 wherein said sample element is connected in series with said power source and with a current detecting resistor, and wherein the means for providing the first voltage comprises an adder, means for providing a first branch signal applied to the adder including an operational amplifier and a capacitor connected to one end of said sample element, and means for providing a second branch signal for application to the adder including a capacitance and a buffer amplifier connected to the other end of said sample element at the function of the sample element and current detecting resistor, whereby the output of the adder provides said first voltage.
Claim 12
Dependent Claim
35 words
A measuring circuit as claimed in claim 10 wherein the means for providing the second voltage comprises an operational amplifier having an input resisTance of kR/(k-1) where the current detecting resistor has a value kR1.
Claim 13
Dependent Claim
37 words
A measuring circuit as claimed in claim 10 wherein the means for providing the second voltage comprises means connecting the output of the buffer amplifier, and an inverter, the output of the inverter providing the second voltage.
References Cited (Backward Citations)
SU189935A1
Cited
US3629700A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-15 | 1977-04-16 | 1977-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-15 | 1981-04-16 | 1981-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-15 | 1985-04-16 | 1985-10-16 | $7700.00 | Window Closed / Lapsed |