US3571703A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Resonance-type inductance or capacitance meter
Assignee: Individual
•
Filing: 1968-10-11
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Granted: 1971-03-23
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Expires: 1988-10-11
Abstract
Abstract An electronic instrument measures properties of inductors by connecting the unknown inductor in an oscillating feedback loop and measuring the frequency of oscillation by means of a pulseaveraging discriminator. Feedback amplifiers are switched to measure inductance and self-oscillation frequency separately. Readout is by means of analogue indicating instruments. A unique control circuit maintains the amplitude of the AC oscillation voltage across the unknown inductor at a constant low value, independently of the inductor''s parameters, and permits the use of large shunt capacitors to minimize errors due to the selfcapacitance of the inductor.
Inventors
- 👤 Alfred Wallace Russell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 23:22
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/26
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
110 words
An impedance measuring instrument comprising: amplifying means having an input terminal and a pair of output terminals; a positive feedback path including an unknown inductor and a capacitive network, said inductor and said network being connected in parallel, said feedback path connected intermediate said output and input terminals to produce oscillations; a variable impedance element, said impedance element connected in said feedback path intermediate said output terminals and said capacitive network to regulate the amplitude of said oscillations to a relatively low and constant value; and indicating means connected to one of said output terminals for indicating the frequency of said oscillations, said means being calibrated in terms of inductance.
Claim 2
Dependent Claim
110 words
An impedance measuring instrument comprising: amplifying means having an input terminal and a pair of output terminals; a positive feedback path including an unknown inductor and a capacitive network, said inductor and said network being connected in parallel, said feedback path connected intermediate said output and input terminals to produce oscillations; a variable impedance element, said impedance element connected in said feedback path intermediate said output terminals and said capacitive network to regulate the amplitude of said oscillations to a relatively low and constant value; and indicating means connected to one of said output terminals for indicating the frequency of said oscillations, said means being calibrated in terms of inductance.
Claim 3
Dependent Claim
41 words
An instrument according to claim 1, wherein said indicating means comprises: a square wave producing circuit fed from one of the output terminals of said amplifying means and feeding a pulse averaging discriminator; and an indicating instrument fed from said discriminator.
Claim 4
Dependent Claim
92 words
An instrument according to claim 1, further comprising a rectifier circuit connected intermediate said output terminals and said variable impedance element and wherein: said amplifying means comprises a first and a second amplifier; said first amplifier supplying power through the other of said output terminals to start and to maintain oscillations in said path; and said second amplifier supplying additional signal voltage through said one of said output terminals to said rectifier circuit controlling said variable impedance element, whereby the buildup and maintenance of the amplitude of said oscillations is made stable.
Claim 5
Dependent Claim
36 words
An instrument according to claim 3, wherein: a capacitor is connected between said one of said output terminals and said rectifier circuit, said variable impedance element being bias controlled by the output of said rectifier circuit.
Claim 6
Dependent Claim
132 words
An instrument according to claim 1, wherein said amplifying means comprises a first and a second amplifier; said first amplifier having said input terminal being connected to provide power gain through the other of said output terminals to said path; said second amplifier being connected to amplify further the output signal of said first amplifier to control said variable impedance element and to feed said indicating means through said one of said output terminals; said instrument further comprises a third amplifier having an input and an output; said input connected to said output terminals adapted to maintain oscillations in said unknown inductor in its self-resonant state; and switch means for coupling the output of said third amplifier to said inductor and said input terminal while decoupling said network from said unknown inductor.
Claim 7
Dependent Claim
31 words
An instrument according to claim 5, wherein: said indicating means includes a pair of indicators, said switch means coupling one of said indicators to said one of sa said output terminals.
Claim 8
Dependent Claim
29 words
The structure of a claim 6, one of said indicators being calibrated in terms of self-resonant frequency, and the other of said indicators being calibrated in terms of inductance.
Claim 9
Dependent Claim
26 words
An instrument according to claim 5, further comprising: a further variable impedance element connected in said feedback path intermediate said third amplifier and said output terminals.
Claim 10
Dependent Claim
15 words
An instrument according to claim 1, wherein said variable impedance element is a field-effect transistor.
References Cited (Backward Citations)
US2999168A
Cited
US3344668A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-03-22 | 1974-09-21 | 1975-03-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-22 | 1978-09-21 | 1979-03-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-22 | 1982-09-21 | 1983-03-23 | $7700.00 | Window Closed / Lapsed |