US3646436A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus and method for measuring electrical resistance employing constant output voltage technique
Assignee: Verizon Laboratories Inc
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Filing: 1969-12-22
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Granted: 1972-02-29
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Expires: 1989-12-22
Abstract
Abstract Technique of measuring resistivity of a specimen by contacting the specimen with a pair of electrodes and passing a constant current from a constant current source through the specimen between the electrodes. The potential drop between the electrodes is detected and employed to control the output of the constant current source so as to produce a potential drop between the electrodes of a predetermined value. The measured constant current from the source which produces the predetermined potential drop is a measure of the resistivity of the specimen between the pair of electrodes.
Inventors
- 👤 Joseph Y Chan
- 👤 Dinesh C Gupta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 12:31
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
159 words
Apparatus for measuring the electrical resistance of a specimen comprising a pair of electrodes for contacting the specimen; a source of constant current connected to the pair of electrodes; control means including sensing means connected to the electrodes for detecting the potential drop therebetween, comparison means connected to the sensing means and operable to produce an output signal indicative of the difference between a predetermined potential and the detected potential drop between the electrodes, and regulating means connected to the comparison means and to said source of constant current and operable in response to the output signal from the comparison means to vary the value of the constant current produced by the source of constant current in a manner to change the value of the potential drop between the electrodes toward the predetermined potential; and current-measuring means for measuring the current flow from the source of constant current when the potential drop between the electrodes equals said predetermined potential.
Claim 2
Dependent Claim
159 words
Apparatus for measuring the electrical resistance of a specimen comprising a pair of electrodes for contacting the specimen; a source of constant current connected to the pair of electrodes; control means including sensing means connected to the electrodes for detecting the potential drop therebetween, comparison means connected to the sensing means and operable to produce an output signal indicative of the difference between a predetermined potential and the detected potential drop between the electrodes, and regulating means connected to the comparison means and to said source of constant current and operable in response to the output signal from the comparison means to vary the value of the constant current produced by the source of constant current in a manner to change the value of the potential drop between the electrodes toward the predetermined potential; and current-measuring means for measuring the current flow from the source of constant current when the potential drop between the electrodes equals said predetermined potential.
Claim 3
Dependent Claim
79 words
Apparatus for measuring the electrical resistance of a specimen in accordance with claim 1 wherein the value of the constant current produced by the source of constant current varies in response to the impedance present at the input thereto; said regulating means includes a variable impedance element connected to the input of the source of constant current; and the value of the impedance of said variable impedance element varies in response to the output signal from the comparison means.
Claim 4
Dependent Claim
103 words
Apparatus for measuring the electrical resistance of a specimen in accordance with claim 2 wherein said comparison means includes a differential amplifier circuit and is operable to produce an output signal proportional to the difference between said predetermined potential and the detected potential drop between the electrodes; and said variable impedance element is a field-effect type transistor having its gate connected to said comparison means and its source and drain coupled to the input of the source of constant current and is operable to provide a value of impedance between the source and drain related to the output signal from the comparison means.
Claim 5
Independent Claim
87 words
The method of measuring the electrical resistance of a specimen including the steps of contacting the specimen with a pair of electrodes; passing a constant electrical current through the specimen between the electrodes; measuring the potential drop between the electrodes; comparing the measured potential drop between the electrodes with a predetermined potential; changing the value of the constant current to change the potential drop between the electrodes to the predetermined potential; and measuring the electrical current when the potential drop between the electrodes equals said predetermined potential.
Claim 6
Independent Claim
87 words
The method of measuring the electrical resistance of a specimen including the steps of contacting the specimen with a pair of electrodes; passing a constant electrical current through the specimen between the electrodes; measuring the potential drop between the electrodes; comparing the measured potential drop between the electrodes with a predetermined potential; changing the value of the constant current to change the potential drop between the electrodes to the predetermined potential; and measuring the electrical current when the potential drop between the electrodes equals said predetermined potential.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-02-28 | 1975-08-30 | 1976-02-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-02-28 | 1979-08-30 | 1980-02-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-02-28 | 1983-08-30 | 1984-02-29 | $7700.00 | Window Closed / Lapsed |