Patent US3652932A successfully refreshed from Google Patents.
US3652932A
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Method and apparatus for measurement of surface charge of an electret
Assignee: AT&T Inc
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Filing: 1970-07-30
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Granted: 1972-03-28
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Expires: 1990-07-30
Abstract
Abstract Electret surface charge is measured accurately and in a reproducible fashion by supporting an electret between fixed electrodes positioned at a finite distance from the electret, one at ground potential and the other employed as a voltage probe. A conductive shutter is interposed between the electret and the probe. A capacitor connecting the electrodes is discharged and the shutter opened to induce a charge on the probe. This charge is drawn from the capacitor and the voltage thus generated across the capacitor is measured with an electrometer. Since electrode spacing is fixed, repeated measurement yields the same measure and the charges on different samples are directly comparable.
Inventors
- 👤 Gerhard Martin Sessler
- 👤 James Edward West
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 07:24
CPC Classifications
H; H01; H01G; H01G7/00; H01G7/02; G; G01; G01N; G01N27/00; G01N27/60; G01R; G01R5/00; G01R5/28; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
119 words
Apparatus for the measurement of the surface charge of an electret, which comprises, first and second electrodes fixedly supported in juxtaposition to one another, the first held at reference ground potential and the second being coupled as a probe to ground by a capacitive system, means for supporting a film electret between said electrodes, conductive shutter means interposed between said probe electrode and said supported electret, means for selectively discharging said capacitive system, means for systematically withdrawing said conductive shutter means from said interposition, thereby to permit a charge to be induced, by virtue of said electret charge, on said probe electrode and drawn from said capacitive system, and means for measuring the voltage developed in said capacitive system.
Claim 2
Dependent Claim
119 words
Apparatus for the measurement of the surface charge of an electret, which comprises, first and second electrodes fixedly supported in juxtaposition to one another, the first held at reference ground potential and the second being coupled as a probe to ground by a capacitive system, means for supporting a film electret between said electrodes, conductive shutter means interposed between said probe electrode and said supported electret, means for selectively discharging said capacitive system, means for systematically withdrawing said conductive shutter means from said interposition, thereby to permit a charge to be induced, by virtue of said electret charge, on said probe electrode and drawn from said capacitive system, and means for measuring the voltage developed in said capacitive system.
Claim 3
Dependent Claim
26 words
Apparatus as defined in claim 1, wherein, said probe electrode has a surface area coextensive with the area of said electret that overlays said first electrode.
Claim 4
Dependent Claim
27 words
Apparatus as defined in claim 1, wherein, said probe electrode has a surface area substantially smaller than the area of said electret that overlays said first electrode.
Claim 5
Dependent Claim
33 words
Apparatus as defined in claim 1, wherein, said probe electrode, said shutter, and said first electrode are coated with a layer of nonoxidizing metal to avoid thE accumulation of erratic space charge thereon.
Claim 6
Dependent Claim
19 words
Apparatus as defined in claim 1, wherein, said film electret is supported at its periphery by a semirigid frame.
Claim 7
Dependent Claim
28 words
Apparatus as defined in claim 1, wherein, said first electrode has a recess in the form of a cuplike depression in its surface juxtaposed to said probe electrode.
Claim 8
Dependent Claim
33 words
Apparatus as defined in claim 1, wherein, said first electrode and said probe electrode are adjustably mounted so that they may be fixedly supported in juxtaposition with prescribed amounts of overlap and separation.
Claim 9
Dependent Claim
137 words
Apparatus for the measurement of surface charge on a film electret, which comprises: an annular conductive support maintained at a first potential, a conductive probe spaced apart from and held in fixed relation to said conductive support, capacitor means interconnecting said probe and said support, means for tautly holding an electret in contact with said annular support, a movable conductive shutter held at said first potential and supported intermediate said probe and said electret for electrically shielding said probe from said electret in a first position and for exposing said probe to said electret in a second position, said shutter having an area at least equal to the area encompassed by said probe, and means for measuring charge accumulated on said capacitor means upon the transfer of said shutter from said first position to said second position.
Claim 10
Dependent Claim
137 words
Apparatus for the measurement of surface charge on a film electret, which comprises: an annular conductive support maintained at a first potential, a conductive probe spaced apart from and held in fixed relation to said conductive support, capacitor means interconnecting said probe and said support, means for tautly holding an electret in contact with said annular support, a movable conductive shutter held at said first potential and supported intermediate said probe and said electret for electrically shielding said probe from said electret in a first position and for exposing said probe to said electret in a second position, said shutter having an area at least equal to the area encompassed by said probe, and means for measuring charge accumulated on said capacitor means upon the transfer of said shutter from said first position to said second position.
Claim 11
Dependent Claim
143 words
Apparatus for the measurement of surface charge on a film electret, which comprises: a conductive ring maintained at a first potential, a shielded plane conductive probe spaced apart from and held in fixed relation to said conductive ring, capacitor means interconnecting said probe and said ring, means for tautly holding a metallized thin film electret in contact with said ring support, a movable conductive electrode held at said first potential and supported intermediate said probe and said electret for electrically isolating said probe from said electret in a first position and for exposing said probe to said electret in a second position, said movable electrode having an area at least equal to an area coextensive with said ring support, and means for measuring charge accumulated on said capacitor means upon the transfer of said shutter from said first position to said second position.
Claim 12
Dependent Claim
143 words
Apparatus for the measurement of surface charge on a film electret, which comprises: a conductive ring maintained at a first potential, a shielded plane conductive probe spaced apart from and held in fixed relation to said conductive ring, capacitor means interconnecting said probe and said ring, means for tautly holding a metallized thin film electret in contact with said ring support, a movable conductive electrode held at said first potential and supported intermediate said probe and said electret for electrically isolating said probe from said electret in a first position and for exposing said probe to said electret in a second position, said movable electrode having an area at least equal to an area coextensive with said ring support, and means for measuring charge accumulated on said capacitor means upon the transfer of said shutter from said first position to said second position.
Claim 13
Independent Claim
97 words
The method of measuring the surface charge on an electret supported between first and second electrodes, which comprises the steps of: interposing a conductive shield between the electret and the first of the electrodes, said shield being maintained at the potential of said second electrode, momentarily electrically interconnnecting said electrodes, withdrawing the shield to expose said one electrode to the charge on the electret, accumulating the charge thereby induced in said one electrode from said electret in a capacitor system, and measuring the charge accumulated in said capacitor system within the time constant of said capacitor system.
Claim 14
Independent Claim
97 words
The method of measuring the surface charge on an electret supported between first and second electrodes, which comprises the steps of: interposing a conductive shield between the electret and the first of the electrodes, said shield being maintained at the potential of said second electrode, momentarily electrically interconnnecting said electrodes, withdrawing the shield to expose said one electrode to the charge on the electret, accumulating the charge thereby induced in said one electrode from said electret in a capacitor system, and measuring the charge accumulated in said capacitor system within the time constant of said capacitor system.
Claim 15
Independent Claim
79 words
The method of measuring the surface charge on an electret supported between a pair of electrodes, which comprises the steps of: exposing one electrode to the field of an electret, interposing a conductive shield between the electret and one of the electrodes, accumulating the charge induced in said one electrode from said electret as a result of said interposition in a capacitor system, and measuring the charge accumulated said capacitor system within the time constant of said capacitor system.
Claim 16
Independent Claim
79 words
The method of measuring the surface charge on an electret supported between a pair of electrodes, which comprises the steps of: exposing one electrode to the field of an electret, interposing a conductive shield between the electret and one of the electrodes, accumulating the charge induced in said one electrode from said electret as a result of said interposition in a capacitor system, and measuring the charge accumulated said capacitor system within the time constant of said capacitor system.
Claim 17
Independent Claim
162 words
The method of mapping the lateral charge distribution of an electret, which comprises the steps of: supporting an electret between a fixed electrode having an area at least coextensive with the area of the electret, and a probe electrode having an area comparable to the smallest area of detail required for said map, interposing a conductive shield between the electret and said probe electrode, momenTarily bringing said fixed electrode and said probe electrode to the same potential, withdrawing the shield to expose said probe electrode to the charge on the underlying area of the electret, accumulating the charge induced in the probe electrode from the electret area in a capacitor system, measuring the charge accumulated in the capacitor system within the time constant of the capacitor system, progressively moving said probe electrode laterally over the surface of said electret, and repeatedly measuring the charge on said capacitor system within the time constant thereof for each area of said electret underlying said probe.
Claim 18
Independent Claim
162 words
The method of mapping the lateral charge distribution of an electret, which comprises the steps of: supporting an electret between a fixed electrode having an area at least coextensive with the area of the electret, and a probe electrode having an area comparable to the smallest area of detail required for said map, interposing a conductive shield between the electret and said probe electrode, momenTarily bringing said fixed electrode and said probe electrode to the same potential, withdrawing the shield to expose said probe electrode to the charge on the underlying area of the electret, accumulating the charge induced in the probe electrode from the electret area in a capacitor system, measuring the charge accumulated in the capacitor system within the time constant of the capacitor system, progressively moving said probe electrode laterally over the surface of said electret, and repeatedly measuring the charge on said capacitor system within the time constant thereof for each area of said electret underlying said probe.
References Cited (Backward Citations)
US3496461A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-03-28 | 1975-09-27 | 1976-03-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-28 | 1979-09-27 | 1980-03-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-28 | 1983-09-27 | 1984-03-28 | $7700.00 | Window Closed / Lapsed |