US3790886A
Expired / Lapsed
US
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Electrical measurement instrument having an improved analog to digital converter
Assignee: Keithley Instruments LLC
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Filing: 1971-10-04
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Granted: 1974-02-05
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Expires: 1991-10-04
Abstract
Abstract An electrical measuring instrument is disclosed which may be used for measuring the magnitude of an unknown source, such as the magnitude of an A.C. signal, or the magnitude and polarity of a D.C. signal, or the resistance of a resistor. A voltage signal is developed having a magnitude dependent on the unknown source and this signal is applied to an analog to digital converter which employs a capacitor, a charging circuit and a discharging circuit. The capacitor charges at a rate dependent on the magnitude of the voltage signal. The stored energy crosses a given level and, then, in response to a clock pulse the capacitor is discharged at a known rate. The capacitor discharges through a particular level and the charging operation is thereafter commenced in response to another clock pulse. Counter and logic circuitry serve to provide an output indication of the magnitude of the unknown source as a function of a relationship of the number of clock pulses occurring during the discharge operations and a fixed number of clock pulses. Autoranging circuitry serves to sequentially uprange and downrange the scaling of the magnitude of an input signal prior to being applied to the analog to digital conversion circuitry. Other features are disclosed.
Inventors
- 👤 S Kurtin
- 👤 M Anthony
- 👤 W Watrous
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:43
CPC Classifications
H; H03; H03M; H03M1/00; G; G01; G01R; G01R1/00; G01R1/30; G01R27/00; G01R27/02; H03M1/06; H03M1/08
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
143 words
Apparatus for converting an analog signal into a digital signal and comprising: energy storage means; charging circuit means for storing energy in said energy storage means at a rate dependent on the magnitude of a said analog signal; discharging circuit means for discharging energy from said energy storage means at a relatively constant rate; means for monitoring said energy storage means and providing an output indication each time said energy storage means charges past a predetermined level in one direction and each time said energy storage means discharges to at least past said predetermined level in the opposite direction; a source of clock pulses; and control means for receiving said clock pulses for controlling said circuit means for alternate charging and discharging operations each commencing in dependence upon concurrent occurrence of a respective one of said output indications and a said clock pulse.
Claim 2
Dependent Claim
143 words
Apparatus for converting an analog signal into a digital signal and comprising: energy storage means; charging circuit means for storing energy in said energy storage means at a rate dependent on the magnitude of a said analog signal; discharging circuit means for discharging energy from said energy storage means at a relatively constant rate; means for monitoring said energy storage means and providing an output indication each time said energy storage means charges past a predetermined level in one direction and each time said energy storage means discharges to at least past said predetermined level in the opposite direction; a source of clock pulses; and control means for receiving said clock pulses for controlling said circuit means for alternate charging and discharging operations each commencing in dependence upon concurrent occurrence of a respective one of said output indications and a said clock pulse.
Claim 3
Dependent Claim
36 words
Apparatus as set forth in claim 1 including means for providing an outPut indication indicative of the magnitude of said analog signal in dependence upon the number of clock pulses occurring during the said discharge operations.
Claim 4
Dependent Claim
45 words
Apparatus as set forth in claim 1 including means for providing an output indication of the magnitude of said analog signal in dependence upon the ratio of the number of clock pulses occurring during the discharging operations and a predetermined number of said clock pulses.
Claim 5
Dependent Claim
79 words
Apparatus as set forth in claim 1 including gating means for providing gated clock pulses during said discharge operations and first and second digital counting means for respectively counting said clock pulses and said gated clock pulses and circuit means for providing an output indication as to the magnitude of a said analog signal in dependence upon the number of counted gated clock pulses occurring during a period in which a predetermined number of said clock pulses are counted.
Claim 6
Dependent Claim
64 words
Apparatus as set forth in claim 4 wherein said first counting means includes means for counting N pulses during each counting cycle of operation, means for controlling said gating means for a predetermined number of said N pulses so that only a corresponding predetermined number of gated clock pulses may be counted by said second counting means during each said counting cycle of operation.
Claim 7
Dependent Claim
48 words
Apparatus as set forth in claim 5 including circuit means controlled by said first timing means once at least said predetermined number of said N pulses have been counted for determining the actual number of said gated clock pulses which have been counted by said second counting means.
Claim 8
Dependent Claim
25 words
Apparatus as set forth in claim 6 including register means for providing a digital manifestation as to said actual number of said gated clock pulses.
Claim 9
Dependent Claim
35 words
Apparatus as set forth in claim 7 including decoder means responsive to said digital representation for providing output signals in accordance with the decimal value thereof, and readout means for providing a corresponding decimal readout.
Claim 10
Dependent Claim
72 words
Apparatus as set forth in claim 7 wherein said digital manifestation is representative of a plural digit decimal number, and decoder means responsive to said digital representation for providing a plurality of patterns of output signals with each said pattern being representative of the decimal value of an associated one of said plural digits, and plural digit readout means responsive to said patterns of output signals for providing a corresponding decimal readout.
Claim 11
Dependent Claim
46 words
Apparatus as set forth in claim 1 wherein said discharging circuit means is connected to said energy storage means and includes switching means for, when actuated, completing a discharge path for said energy storage means to a reference point exhibiting a substantially constant D.C. voltage level.
Claim 12
Dependent Claim
71 words
Apparatus as set forth in claim 1 including input circuit means for receiving a said analog signal and output circuit means for applying a unipolar analog signal to said energy storage means, unipolar circuit means interposed between said input and output circuit means for providing at said output circuit means a unipolar analog signal of a given polarity and of a magnitude dependent on that of a received said analog signal.
Claim 13
Dependent Claim
50 words
Apparatus as set forth in claim 11 wherein said discharge circuit means is connected to said energy storage means and includes switching means for, when actuated, completing a discharge path to a reference point exhibiting a substantially constant potential and of a polarity opposite from that of said given polarity.
Claim 14
Dependent Claim
41 words
Apparatus as set forth in claim 12 wherein said switching means includes a first semiconductor means normally reverse biased and wherein said control means includes circuit means for forward biasing said semiconductor means to complete said discharge path for discharging operations.
Claim 15
Dependent Claim
23 words
Apparatus as set forth in claim 11 wherein said unipolar circuit means includes active rectifier means for providing a said unipolar analog signal.
Claim 16
Dependent Claim
26 words
Apparatus as seT forth in claim 14 including polarity sensor means for providing an output indication as to the polarity of a received said analog signal.
Claim 17
Dependent Claim
26 words
Apparatus as set forth in claim 1 including input signal scaling means preceeding said energy storage means for scaling the amplitude of a said analog signal.
Claim 18
Dependent Claim
40 words
Apparatus as set forth in claim 16 wherein said scaling means includes a plurality of selectable scaling circuits for respectively different ranges of values of the amplitude of a said analog signal, and control means for selecting said scaling circuits.
Claim 19
Dependent Claim
51 words
Apparatus as set forth in claim 17, wherein said control means includes circuit means for selecting said scaling circuits in such a manner that said apparatus is sequentially upranged as the magnitude of a said analog signal increases and is sequentially downranged as the magnitude of a said analog signal decreases.
Claim 20
Dependent Claim
46 words
Apparatus as set forth in claim 18, wherein said control means includes decoding means responsive to an outrange indication that a said analog signal has a magnitude beyond the uppermost range of operation, and means for providing a visual indication in response to said outrange indication.
Claim 21
Dependent Claim
90 words
Apparatus as set forth in claim 1 including digital output circuit means for providing an output indication of the magnitude of a said analog signal in dependence upon the number of clock pulses occurring during such discharge operations over a counting cycle dependent on a fixed number of clock pulses, said digital output circuit means including maximum value detecting means for providing an output indication when the analog signal exceeds a predetermined level, and scaling means responsive to a said output indication for scaling the magnitude of said analog signal.
Claim 22
Dependent Claim
175 words
Apparatus for converting an analog signal into a digital signal and comprising: energy storage means; first circuit means for continuously applying energy to said storage means to be stored thereby and at a rate dependent on the magnitude of a said analog signal; second circuit means for periodically discharging energy from said energy storage means at a relatively constant rate; means for monitoring said energy storage means and providing a first output indication each time said stored energy increases past a predetermined level in one direction and a second output indication each time said stored energy decreases to at least past said predetermined level in the opposite direction; a source of clock pulses; and control means for receiving said clock pulses for controlling said second circuit means for periodically discharging energy from said storage means so that each discharge period commences in dependence upon concurrent occurrence of a said first output indication and a said clock pulse and terminates in dependence upon concurrent occurrence of a said second output indication and a said clock pulse.
Claim 23
Dependent Claim
175 words
Apparatus for converting an analog signal into a digital signal and comprising: energy storage means; first circuit means for continuously applying energy to said storage means to be stored thereby and at a rate dependent on the magnitude of a said analog signal; second circuit means for periodically discharging energy from said energy storage means at a relatively constant rate; means for monitoring said energy storage means and providing a first output indication each time said stored energy increases past a predetermined level in one direction and a second output indication each time said stored energy decreases to at least past said predetermined level in the opposite direction; a source of clock pulses; and control means for receiving said clock pulses for controlling said second circuit means for periodically discharging energy from said storage means so that each discharge period commences in dependence upon concurrent occurrence of a said first output indication and a said clock pulse and terminates in dependence upon concurrent occurrence of a said second output indication and a said clock pulse.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-04 | 1977-08-06 | 1978-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-04 | 1981-08-06 | 1982-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-04 | 1985-08-06 | 1986-02-05 | $7700.00 | Window Closed / Lapsed |