US4093915A
Expired / Lapsed
US
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Capacitance measuring system
Assignee: Setra Systems LLC
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Filing: 1977-06-29
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Granted: 1978-06-06
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Expires: 1997-06-29
Abstract
Abstract A system for generating a signal linearly related to the capacitive reactance of a sensor capacitor. The system includes an oscillator for providing an oscillatory signal characterized by a peak-to-peak voltage proportional to an applied control signal, at least one capacitive network and associated peak detecting network, and a feedback network. The capacitive network includes a drive capacitor and a sensor capacitor connected in series between the oscillator and a reference potential, and the peak detector includes means to generate a peak signal representative of the peak-to-peak voltage at the junction between its associated coupling and sensor capacitor. The feedback network produces the control signal for the oscillator whereby the peak amplitude of the voltage across the drive capacitor is constant.
Inventors
- 👤 Dennis K. Briefer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 18:49
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/26; G01R27/2605
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
233 words
A capacitance measuring system comprising: A. an oscillator including means for providing at an output terminal an oscillatory signal relative to a ground potential, said oscillatory signal being characterized by a predetermined peak-to-peak voltage, B. a first capacitive network and associated first peak detecting network, said first capacitive network including a coupling capacitor and a first sensor capacitor connected in series between said output terminal and said ground potential, said first sensor capacitor having one terminal connected to said ground potential, and said first peak detecting network being connected to the junction between said coupling and first sensor capacitors and including means to generate a first peak signal representative of the peak-to-peak voltage at said junction, C. a second capacitive network and associated second peak detecting network, said second capacitive network including a coupling capacitor and a second sensor capacitor connected in series between said output terminal and said ground potential, said second sensor capacitor having one terminal connected to said ground potential, and said second peak detecting network being connected to the junction between said coupling and second sensor capacitors and including means to generate a second peak signal signal representative of the peak-to-peak voltage at said junction, D. combining means coupled to an output terminal of said first and second peak detecting networks for producing an output signal representative of the difference in magnitude of said first and second peak signals.
Claim 2
Dependent Claim
233 words
A capacitance measuring system comprising: A. an oscillator including means for providing at an output terminal an oscillatory signal relative to a ground potential, said oscillatory signal being characterized by a predetermined peak-to-peak voltage, B. a first capacitive network and associated first peak detecting network, said first capacitive network including a coupling capacitor and a first sensor capacitor connected in series between said output terminal and said ground potential, said first sensor capacitor having one terminal connected to said ground potential, and said first peak detecting network being connected to the junction between said coupling and first sensor capacitors and including means to generate a first peak signal representative of the peak-to-peak voltage at said junction, C. a second capacitive network and associated second peak detecting network, said second capacitive network including a coupling capacitor and a second sensor capacitor connected in series between said output terminal and said ground potential, said second sensor capacitor having one terminal connected to said ground potential, and said second peak detecting network being connected to the junction between said coupling and second sensor capacitors and including means to generate a second peak signal signal representative of the peak-to-peak voltage at said junction, D. combining means coupled to an output terminal of said first and second peak detecting networks for producing an output signal representative of the difference in magnitude of said first and second peak signals.
Claim 3
Dependent Claim
50 words
The system according to claim 1 wherein said oscillator includes an oscillatory signal generator coupled through an amplitude limiter to said output terminal, whereby said limiter restricts voltage excursions of the signal produced by said generator to be within predetermined upper and lower limit values defining said predetermined peak-to-peak voltage.
Claim 4
Dependent Claim
119 words
The system according to claim 2 wherein said limiter includes first branch connected between said output terminal and a first reference potential, and a second branch connected between said output terminal and a second reference potential, said first reference potential being greater than said second reference potential, and wherein said first branch includes at least one branch diode arranged to be forward conducting from said output terminal to said first reference potential when the voltage at said terminal equals said upper limit value, and wherein said second branch includes at least one branch diode arranged to be forward conducting from said second reference potential to said output terminal when the voltage at said terminal equals said lower limit value.
Claim 5
Dependent Claim
79 words
The system according to claim 3 wherein said first and second peak detecting networks include a pair of series arranged diodes connected in parallel with a capacitor between said peak detecting network output terminal and a reference potential, and wherein the junction between said series diodes is connected to the junction between the coupling and sensor capacitors associated with each peak detecting network whereby temperature induced changes in the forward voltage drops across said branch diodes are substantially offset.
Claim 6
Dependent Claim
53 words
The system according to claim 1 further comprising a feedback means for applying a feedback signal to said oscillator said, feedback signal being proportional to said output signal, and wherein said oscillator includes means responsive to said feedback signal to control said predetermined peak-to-peak voltage to be functionally related to said feedback signal.
Claim 7
Dependent Claim
67 words
The system according to claim 5 wherein said oscillator includes an oscillatory signal generator coupled through an amplitude limited to said output terminal, whereby said limiter restricts the peak voltage excursions of the signal produced by said generator to be within predetermined upper and lower limit values defining said predetermined peak-to-peak voltage, at least one of said upper and lower limits being related to said feedback signal.
Claim 8
Dependent Claim
119 words
The system according to claim 6 wherein said limiter includes first branch connected between said output terminal and a first reference potential, and a second branch connected between said output terminal and a second reference potential, said first reference potential being greater than said second reference potential, and wherein said first branch includes at least one branch diode arranged to be forward conducting from said output terminal to said first reference potential when the voltage at said terminal equals said upper limit value, and wherein said second branch includes at least one branch diode arranged to be forward conducting from said second reference potential to said output terminal when the voltage of said terminal equals said lower limit value.
Claim 9
Dependent Claim
79 words
The system according to claim 7 wherein said first and second peak detecting networks include a pair of series arranged diodes connected in parallel with a capacitor between said peak detecting network output terminal and a reference potential, and wherein the junction between said series diodes is connected to the junction between the coupling and sensor capacitors associated with each peak detecting network whereby temperature induced changes in the forward voltage drops across said branch diodes are substantially offset.
Claim 10
Independent Claim
186 words
A system for generating a signal functionally related to the capacitive reactance of a sensor capacitor, comprising: A. a first capacitive network and associated first peak detecting network, said first capacitive network including a first drive capacitor and a first sensor capacitor connected in series between a system input terminal and a first reference potential, and said associated peak detecting network being connected to the junction between said first drive and first sensor capacitors and including means for generating a peak signal representative of the peak voltage at said junction, B. an oscillator coupled to said system input terminal and having a control terminal, said oscillator including means to generate an oscillatory signal at said system input terminal, said oscillatory signal being characterized by an amplitude proportional to the voltage at said control terminal, and C. feedback network coupled between said first peak detecting network and said control terminal, said feedback network including means responsive to said peak signal and a second reference potential to apply a feedback signal to said control terminal whereby the peak amplitude of the voltage across said drive capacitor is constant.
Claim 11
Independent Claim
186 words
A system for generating a signal functionally related to the capacitive reactance of a sensor capacitor, comprising: A. a first capacitive network and associated first peak detecting network, said first capacitive network including a first drive capacitor and a first sensor capacitor connected in series between a system input terminal and a first reference potential, and said associated peak detecting network being connected to the junction between said first drive and first sensor capacitors and including means for generating a peak signal representative of the peak voltage at said junction, B. an oscillator coupled to said system input terminal and having a control terminal, said oscillator including means to generate an oscillatory signal at said system input terminal, said oscillatory signal being characterized by an amplitude proportional to the voltage at said control terminal, and C. feedback network coupled between said first peak detecting network and said control terminal, said feedback network including means responsive to said peak signal and a second reference potential to apply a feedback signal to said control terminal whereby the peak amplitude of the voltage across said drive capacitor is constant.
Claim 12
Dependent Claim
102 words
The system according to claim 9 wherein said first drive capacitor is coupled between said oscillator and said peak detecting network and wherein said feedback network includes a differential amplifier network having a non-inverting input terminal, and inverting input terminal, and an output terminal, said non-inverting terminal being coupled to said second reference potential, and said inverting terminal being coupled by resistor R A to said peak detecting network, and said output terminal being coupled to said control terminal by a feedback path and further being coupled to said inverting input terminal by resistor R B wherein R A =R B .
Claim 13
Dependent Claim
113 words
The system according to claim 9 wherein said first drive capacitor is coupled between said oscillator and said peak detecting network and wherein said feedback network includes: i. combining means coupled to said peak detecting network for generating a signal representative of the sum of said peak voltage and a predetermined constant voltage, ii. differential amplifier network having a noninverting input terminal, and inverting input terminal, and an output terminal, said noninverting terminal being coupled to said combining network and said peak detecting network, said inverting terminal being coupled to said output terminal by a first feedback path, and said output terminal being coupled to said control terminal by a second feedback path.
Claim 14
Dependent Claim
96 words
A system according to claim 11 wherein said peak detecting network and combining network comprise two series connected diodes coupled in the same direction between said second potential and said non-inverting input terminal, with the junction between said diodes being connected to said junction between said first drive and first sensor capacitors, and wherein the constant of proportionality relating the amplitude of said oscillatory signal and said voltage at said amplifier output terminal is unity, whereby said voltage at said amplifier output terminal is a linear function of the capacitive reactance of said first sensor capacitor.
Claim 15
Dependent Claim
129 words
A system according to claim 11 wherein said peak detecting network comprises two series connected diodes coupled in the same direction between said first reference potential and a system output terminal, with the junction between said diodes being connected to the junction between said first coupling and first sensor capacitors, and wherein said combining network comprises a first resistor (R1) connected between said system output terminal and said non-inverting terminal, and a second resistor (R2) connected between said second reference potential and said non-inverting terminal, and wherein the constant of proportionality relating the amplitude of said oscillatory signal and said voltage at said amplifier output terminal equals (R1 + R2/(R1), whereby the voltage at said system output terminal is proportional to the capacitive reactance of said first sensor capacitor.
Claim 16
Dependent Claim
107 words
A system according to claim 9 wherein said first sensor capacitor is coupled between said oscillator and said peak detecting network, and wherein said feedback network includes: i. combining means coupled to said peak detecting network for generating a signal representative of the difference of said peak voltage and a predetermined constant voltage, ii. differential amplifier network having a noninverting input terminal, and inverting-input terminal, and an output terminal, said noninverting terminal being coupled to said combining network, and said inverting terminal being coupled to said output terminal by a capacitive feedback path, and said output terminal being coupled to said control terminal by a feedback path.
Claim 17
Dependent Claim
129 words
A system according to claim 14 wherein said peak detecting network and combining network comprise two series connected diodes coupled in the same direction between said first reference potential and said non-inverting input terminal, with the junction between said diodes being connected to said junction between said first drive and first sensor capacitors, and wherein said combining network comprises a first resistor connected between said peak detector and said non-inverting terminal, and a second resistor connected between said second reference potential and said non-inverting terminal, and wherein the constant of proportionality relating the amplitude of said oscillatory signal and said voltage at said amplifier output terminal is unity, whereby said voltage at said amplifier output terminal is a linear function of the capacitive reactance of said first sensor capacitor.
Claim 18
Dependent Claim
91 words
A system according to claim 9 wherein said first sensor capacitor is coupled between said oscillator and said peak detecting network, and wherein said feedback network includes differential amplifier network having a non-inverting input terminal, and inverting input terminal, and an output terminal, said non-inverting terminal being coupled to said second reference potential, and said inverting terminal being coupled to said peak detecting network and being further coupled to said output terminal by a capacitive feedback path, and said output terminal being coupled to said control terminal by a feedback path.
Claim 19
Dependent Claim
94 words
A system according to claim 16 wherein said peak detecting network comprises two series connected diodes coupled in the same direction between said first reference potential and said non-inverting input terminal, with the junction between said diodes being connected to said junction between said first drive and first sensor capacitors, and wherein the constant of proportionality relating the amplitude of said oscillatory signal and said voltage at said amplifier output terminal is unity, whereby said voltage at said amplifier output terminal is a linear function of the capacitive reactance of said first sensor capacitor.
Claim 20
Dependent Claim
209 words
A system according to claim 9 wherein said first drive capacitor is coupled between said oscillator and said first peak detecting network. and wherein said feedback network includes: i. combining means coupled to said peak detecting network for generating a signal representative of the sum of said peak voltage and a predetermined constant voltage, ii. differential amplifier network having a noninverting input terminal, and inverting input terminal, and an output terminal, said noninverting terminal being couples to said combining network and said first peak detecting network, and said inverting terminal being coupled to said output terminal by a capacitive feedback path, and said output terminal being coupled to said control terminal by a feedback path, and further comprising: second capacitive network and associated peak detecting network, said second capacitive network including a second drive capacitor and a secnd capacitor between sais system input terminal and said first reference potential, and said associated peak detecting network being connected to the junction between said second drive and second sensor capacitors, said second drive capacitor being coupled between said oscillator and said peak detecting network, and said peak detecting network including means for generating a signal representative of the peak voltage at said junction and applying that signal to said inverting terminal.
Claim 21
Dependent Claim
116 words
A system according to claim 18 wherein said first peak detecting network and combining network comprise two series connected diodes coupled in the same direction between said second reference potential and said non-inverting terminal, with the junction between said diodes being connected to said junction between said first drive and first sensor capacitors, and wherein said second peak detecting network comprises two series connected diodes coupled in the same direction between said first reference potential and said inverting terminal, with the junction between said diodes being connected to the junction between said first coupling and first sensor capacitors, whereby the voltage at said non-inverting terminal is proportioned to the capacitive reactance of said first sensor capacitor.
Claim 22
Dependent Claim
126 words
A system according to claim 18 wherein said first peak detecting network comprises two series connected diodes coupled in the same direction between first reference potential and a system output terminal, with the junction between said diodes being connected to said junction between said first drive and first sensor capacitors, and wherein said combining network comprises a first resistor connected between said system output terminal and said noninverting terminal, and a second resistor connected between a reference potential and said non-inverting terminal, and wherein said second peak detecting network comprises two series connected diodes coupled in the same direction between first reference potential and said inverting terminal, with the junction between said diodes being connected to said junction between said first drive and first sensor capacitors.
Claim 23
Dependent Claim
32 words
A system according to claim 20 wherein R A = R B , whereby the voltage at said system output terminal is proportional to the capacitive reactance of said first sensor capacitor.
Claim 24
Dependent Claim
207 words
A system according to claim 9 wherein said first drive capacitor is coupled between said oscillator and said first peak detecting network, and further comprising: second capacitive network and associated peak detecting network, said second capacitive network including a second drive capacitor and a second capacitor between said system input terminal and said first reference potential, and said associated peak detecting network being connected to the junction between said second drive and second sensor capacitors, said second drive capacitor being coupled between said oscillator and said peak detecting network, and said peak detecting network including means for generating a signal representative of the peak voltage at said junction between said second drive and second sensor capacitors, wherein said feedback network includes: i. combining means coupled to said first and second peak detecting networks for generating a combined signal representative of the difference of said peak voltages, ii. differential amplifier network having a noninverting input terminal, and inverting input terminal, and an output terminal, said inverting terminal being coupled to said combining network, said non-inverting terminal being coupled to said second reference potential, and said output terminal being coupled to said control terminal by a first feedback path and to said inverting terminal by a second feedback path.
Claim 25
Dependent Claim
143 words
A system according to claim 22 wherein said first peak detecting network and combining network comprise a first pair of diodes coupled in series in the same direction between said first reference potential and said combining network, with the junction between said diodes being connected to said junction between said first drive and first sensor capacitors, and wherein said second peak detecting network comprises a second pair of diodes coupled in series in the same direction between said first reference potential and said inverting terminal, with the junction between said diodes being connected to the junction between said first coupling and first sensor capacitors wherein one of said pairs of diodes is adapted to pass current to said first reference potential when forward biased, and the other of said pairs is adapted to pass current from said first reference potential when forward biased.
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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) | 1981-06-05 | 1981-12-05 | 1982-06-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-06-05 | 1985-12-05 | 1986-06-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-06-05 | 1989-12-05 | 1990-06-06 | $7700.00 | Window Closed / Lapsed |