Patent US3935531A successfully refreshed from Google Patents.
US3935531A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrometer with low voltage indicator
Assignee: Xerox Corp
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Filing: 1974-12-16
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Granted: 1976-01-27
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Expires: 1994-12-16
Abstract
Abstract An electrometer system particularly adapted for non-contact measurement of electrostatic charges in electrostatography, such as the charge level on photoreceptor surface areas in xerographic machines. The electrometer circuit has a very high impedance normally floating input, and a simple D.C. measurement circuit. The measurement circuit output can be read by a conventional test meter. The electrometer is controlled by a simple switching arrangement providing an automatic zeroing position in which the initial level of the input circuit is automatically reset by a feedback amplifier from the output to compensate for any temperature induced or other variations in the measurement circuit. The power supply voltage is automatically monitored and the output meter is driven to a non-zeroing position in response to a low supply voltage by a feedback amplifier circuit operative only in the zeroing position, overriding the automatic zeroing circuit.
Inventors
- 👤 Robert J. Slomcenski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 02:52
CPC Classifications
G; G01; G01R; G01R29/00; G01R29/24; G01R29/12; Y; Y10; Y10S; Y10S320/00; Y10S320/18
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
206 words
In an electrometer system for non-contact detection of an electrostatic charge comprising a probe electrode and an electrometer circuit having a power supply voltage and including an electrically floating input circuit for said probe electrode, said electrometer circuit providing an output signal to an output level indicator means indicating a voltage on said probe electrode, and wherein said electrometer circuit has zeroing means and switch means selectively connecting said zeroing means with said input circuit for normally providing zeroing of said indicator means with a zero output signal, the improvement comprising: reference voltage means providing a reference voltage, inhibited voltage comparison means comparing said power supply voltage against said reference voltage and providing an indicator signal output only in response to said power supply voltage falling below said reference voltage; and connecting means for connecting said inhibited voltage comparison means to said input circuit when said switch means is connecting said zeroing means to said input circuit to provide a non-zero output signal only when said indicator signal is produced by said inhibited voltage comparison means, said non-zero output signal corresponding to said indicator signal and being indicated by said indicator means during said normal zeroing of said indicator means, indicating a low power supply voltage.
Claim 2
Dependent Claim
206 words
In an electrometer system for non-contact detection of an electrostatic charge comprising a probe electrode and an electrometer circuit having a power supply voltage and including an electrically floating input circuit for said probe electrode, said electrometer circuit providing an output signal to an output level indicator means indicating a voltage on said probe electrode, and wherein said electrometer circuit has zeroing means and switch means selectively connecting said zeroing means with said input circuit for normally providing zeroing of said indicator means with a zero output signal, the improvement comprising: reference voltage means providing a reference voltage, inhibited voltage comparison means comparing said power supply voltage against said reference voltage and providing an indicator signal output only in response to said power supply voltage falling below said reference voltage; and connecting means for connecting said inhibited voltage comparison means to said input circuit when said switch means is connecting said zeroing means to said input circuit to provide a non-zero output signal only when said indicator signal is produced by said inhibited voltage comparison means, said non-zero output signal corresponding to said indicator signal and being indicated by said indicator means during said normal zeroing of said indicator means, indicating a low power supply voltage.
Claim 3
Dependent Claim
43 words
The electrometer system of claim 1, wherein said zeroing means is automatic, and wherein said connecting means contains signal override means for overriding said zeroing means with said indicator signal only when said indicator signal is produced by said inhibited voltage comparison means.
Claim 4
Dependent Claim
17 words
The electrometer system of claim 1, wherein said connecting means is a part of said switch means.
Claim 5
Dependent Claim
31 words
The electrometer system of claim 1, wherein said inhibited voltage comparison means comprises an operational amplifier and rectifying means in the output of the operational amplifier providing inhibition of said output.
Claim 6
Dependent Claim
20 words
The electrometer system of claim 2, wherein said automatic zeroing means connects with said input circuit through said connecting means.
Claim 7
Dependent Claim
38 words
The electrometer system of claim 5, wherein said override means comprises a resistor connecting between said automatic zeroing means and said inhibited voltage comparison means but not connecting between said inhibited voltage comparison means and said input circuit.
Claim 8
Dependent Claim
34 words
The electrometer system of claim 1, wherein said indicator signal from said inhibited voltage comparison means drives said output signal and said indicator means to a substantial portion of the full output level thereof.
References Cited (Backward Citations)
US3118137A
Cited
US3832629A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-01-26 | 1979-07-28 | 1980-01-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-01-26 | 1983-07-28 | 1984-01-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-01-26 | 1987-07-28 | 1988-01-27 | $7700.00 | Window Closed / Lapsed |