US3944920A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Current measurement
Assignee: Taylor Servomex Ltd
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Filing: 1974-08-07
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Granted: 1976-03-16
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Expires: 1994-08-07
Abstract
Abstract An apparatus for measuring small currents in which the current is applied to an integrator. The integrator output is applied to a slope detecting means, preferably differentiator and the integrator output is reduced at intervals to zero.
Inventors
- 👤 Alan John Borer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 21:46
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/34; H03F3/343; H03F3/347; G; G01; G01R; G01R19/00; G01R19/0023; G01R19/12; G06; G06G; G06G7/00; G06G7/12; G06G7/14; G06G7/18
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
206 words
An apparatus responding to the value of a small input current, comprising input terminals for said input current and output terminals, and an integrator, said integrator having an integrator input coupled to said input terminals, and an output, said integrator comprising an amplifier connected in a path between input and output of said integrator and a capacitor, whereby said integrator produces on said capacitor a voltage which is the continuing integral of an input current applied to said input terminals, said apparatus further comprising a differentiator having an input coupled to the integrator output and an output, to differentiate continuously the voltage at the integrator output whilst the voltage at said integrator output is varying, and an output coupled to said output terminals whereby an output is obtained at said output terminals which is directly proportional to said input current, said apparatus further including switching means associated with the input to said integrator, said switching means being of a nature to produce by its operation an unwanted input to said integrator and comprising means for developing a correction signal the effect of which is equal and opposite that of said unwanted signal, and, on operation of said switching means injecting said correction signal into said input.
Claim 2
Independent Claim
206 words
An apparatus responding to the value of a small input current, comprising input terminals for said input current and output terminals, and an integrator, said integrator having an integrator input coupled to said input terminals, and an output, said integrator comprising an amplifier connected in a path between input and output of said integrator and a capacitor, whereby said integrator produces on said capacitor a voltage which is the continuing integral of an input current applied to said input terminals, said apparatus further comprising a differentiator having an input coupled to the integrator output and an output, to differentiate continuously the voltage at the integrator output whilst the voltage at said integrator output is varying, and an output coupled to said output terminals whereby an output is obtained at said output terminals which is directly proportional to said input current, said apparatus further including switching means associated with the input to said integrator, said switching means being of a nature to produce by its operation an unwanted input to said integrator and comprising means for developing a correction signal the effect of which is equal and opposite that of said unwanted signal, and, on operation of said switching means injecting said correction signal into said input.
Claim 3
Dependent Claim
61 words
An apparatus in accordance with claim 1, wherein said switching means is a field effect transistor, and said unwanted signal is due to a capacitance of said transistor, and wherein the means for developing said correction signal includes a capacitor and further switching means for injecting into said injector input a current due to a change of charge on said capacitor.
Claim 4
Dependent Claim
92 words
An apparatus in accordance with claim 1, and including a feedback path from an output of said integrator to the input of said integrator, said feedback path including a second integrator whereby said second integrator is effective to produce at said first integrator input a signal component, applied in opposition to the input current to be measured, the loop circuit including both said integrators having gain, whereby the input to the first integrator tends to remain substantially constant, the output from said apparatus being derived from the output of said first integrator.
Claim 5
Dependent Claim
22 words
An apparatus in accordance with claim 1 and including means for injecting a steady bias current into the input of said integrator.
Claim 6
Dependent Claim
65 words
An apparatus in accordance with claim 1 and including means for deriving from the input current an inverse current of equal amplitude and opposite polarity, said switching means alternately applying the input and inverse currents to said integrator means, a phase inverter connection to the output of said integrator and selecting means for selectig the signal at the input or output of said phase inverter.
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) | 1979-03-16 | 1979-09-15 | 1980-03-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-03-16 | 1983-09-15 | 1984-03-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-03-16 | 1987-09-15 | 1988-03-16 | $7700.00 | Window Closed / Lapsed |