US3577072A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bridge circuit for differentially measuring capacitance
Assignee: HP Inc
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Filing: 1968-11-19
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Granted: 1971-05-04
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Expires: 1988-11-19
Abstract
Abstract An AC bridge includes two variable capacitors and two complementary conductivity transistors. The two transistors conduct during opposite one-half cycles of the AC bridge excitation voltage to alternately couple the two capacitors in circuit with a load resistor. When either one of the capacitors is not coupled to the load, it is clamped to a source of reference potential by a diode. The output across the load is proportional to the difference in value between the two capacitors.
Inventors
- 👤 Arthur Miller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 15:12
CPC Classifications
G; G01; G01R; G01R17/00; G01R17/10; G01R17/16; G01R27/00; G01R27/02; G01R27/26; G01R27/2605
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
146 words
A circuit for providing an output proportional to the difference between two variable reactance elements comprising: a bridge including: input terminal means connectable to an AC excitation voltage source; output terminal means connectable to a load; two parallel pairs of adjacent arms, each of said pairs being connected between said input and output terminal means, one arm of each pair including one of said two variable reactance elements, and the other adjacent arm of each pair including a transistor; means for biasing the transistors in said two pairs of adjacent arms to conduct alternately during successive half cycles of said AC signal source; a source of reference potential; means for clamping the reactance element in either pair of adjacent arms to said source of reference potential during the one-half cycle of said AC signal when the transistor in the other pair of adjacent arms is conducting.
Claim 2
Dependent Claim
146 words
A circuit for providing an output proportional to the difference between two variable reactance elements comprising: a bridge including: input terminal means connectable to an AC excitation voltage source; output terminal means connectable to a load; two parallel pairs of adjacent arms, each of said pairs being connected between said input and output terminal means, one arm of each pair including one of said two variable reactance elements, and the other adjacent arm of each pair including a transistor; means for biasing the transistors in said two pairs of adjacent arms to conduct alternately during successive half cycles of said AC signal source; a source of reference potential; means for clamping the reactance element in either pair of adjacent arms to said source of reference potential during the one-half cycle of said AC signal when the transistor in the other pair of adjacent arms is conducting.
Claim 3
Dependent Claim
61 words
The circuit of claim 1, each pair of adjacent arms being connected together at a common junction point, said transistors being of complementary conductivity-type and each of said transistors having an emitter electrode connected to the corresponding one of said common junction points, a collector electrode connected to said output terminal means, and a base electrode connected to said biasing means.
Claim 4
Dependent Claim
41 words
The circuit of claim 2, said biasing means including two opposite polarity DC voltage sources connected respectively to the base electrodes of said complementary conductivity transistors; and said clamping means including oppositely poled diodes connected respectively to said common junction points.
Claim 5
Dependent Claim
17 words
The circuit of claim 2, wherein each of said two variable reactance elements is a variable capacitor.
Claim 6
Dependent Claim
43 words
The circuit of claim 4, further including: load resistance means connected to said output terminals means; and means for measuring the output voltage developed across said load resistance means, said output voltage being indicative of the difference in capacitance between said variable capacitors.
Claim 7
Dependent Claim
18 words
The circuit of claim 5, further including filter capacitor means connected in parallel with said load resistance means.
References Cited (Backward Citations)
US3012192A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-05-03 | 1974-11-02 | 1975-05-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-05-03 | 1978-11-02 | 1979-05-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-05-03 | 1982-11-02 | 1983-05-04 | $7700.00 | Window Closed / Lapsed |