US4471300A
Expired / Lapsed
US
⏱️ 0.0 years remaining
LDC Hook-on digital ammeter
Assignee: General Electric Co
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Filing: 1981-07-24
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Granted: 1984-09-11
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Expires: 2001-07-24
Abstract
Abstract A low cost hook-on ammeter for consumer use includes a split core to be clipped around a conductor. Secondary turns on the core actuate a liquid crystal digital display to indicate alternating current amplitude in the conductor. The liquid crystal display segments may be connected to individual taps on the secondary winding, or to taps on a resistive divider network connected across the entire secondary winding. As current in the conductor increases, secondary voltage increases, turning on an increasing number of segments of the liquid crystal display accordingly.
Inventors
- 👤 John D. Harnden, Jr.
- 👤 William P. Kornrumpf
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 03:39
CPC Classifications
G; G01; G01R; G01R13/00; G01R13/40; G01R13/404; G01R13/407; G01R15/00; G01R15/14; G01R15/18; G01R15/186
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
106 words
A hook-on digital ammeter comprising: an annular magnetic core interrupted at at least one location such that the core material at opposite sides of the interruption is sufficiently separable to allow passage of a conductor through the interruption; a secondary winding wound on said core; liquid crystal display means comprising a plurality of display segments having a common connection; a tapped voltage divider network coupled in parallel with said secondary winding, said tapped network having a terminal coupled to said common connection; and resistor means coupling a separate tap, respectively, on said voltage divider network to a separate segment of said liquid crystal display means, respectively.
Claim 2
Dependent Claim
106 words
A hook-on digital ammeter comprising: an annular magnetic core interrupted at at least one location such that the core material at opposite sides of the interruption is sufficiently separable to allow passage of a conductor through the interruption; a secondary winding wound on said core; liquid crystal display means comprising a plurality of display segments having a common connection; a tapped voltage divider network coupled in parallel with said secondary winding, said tapped network having a terminal coupled to said common connection; and resistor means coupling a separate tap, respectively, on said voltage divider network to a separate segment of said liquid crystal display means, respectively.
Claim 3
Dependent Claim
15 words
The digital ammeter of claim 1 wherein said voltage divider network comprises a resistive network.
Claim 4
Dependent Claim
32 words
The digital ammeter of claim 2 wherein said liquid crystal display means is fabricated on a substrate and wherein said circuit means comprises a thin film resistor network deposited on said substrate.
Claim 5
Dependent Claim
13 words
The digital ammeter of claim 2 wherein said display segments comprise bargraph elements.
Claim 6
Dependent Claim
92 words
A digital ammeter for measuring alternating current in a conductor, said ammeter comprising: an annular magnetic core encircling said conductor carrying alternating current; a secondary winding wound on said core; a liquid crystal display means comprising a plurality of display segments having a common connection; a tapped voltage divider network coupled in parallel with said secondary winding, said tapped network having a terminal coupled to said common connection; and resistor means coupling a separate tap, respectively, on said voltage divider network to a separate segment of said liquid crystal display means, respectively.
Claim 7
Dependent Claim
92 words
A digital ammeter for measuring alternating current in a conductor, said ammeter comprising: an annular magnetic core encircling said conductor carrying alternating current; a secondary winding wound on said core; a liquid crystal display means comprising a plurality of display segments having a common connection; a tapped voltage divider network coupled in parallel with said secondary winding, said tapped network having a terminal coupled to said common connection; and resistor means coupling a separate tap, respectively, on said voltage divider network to a separate segment of said liquid crystal display means, respectively.
Claim 8
Dependent Claim
15 words
The digital ammeter of claim 5 wherein said voltage divider network comprises a resistive network.
Claim 9
Dependent Claim
32 words
The digital ammeter of claim 6 wherein said liquid crystal display means is fabricated on a substrate and wherein said circuit means comprises a thin film resistor network deposited on said substrate.
Claim 10
Dependent Claim
13 words
The digital ammeter of claim 5 wherein said display segments comprise bargraph elements.
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) | 1987-09-11 | 1988-03-12 | 1988-09-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-09-11 | 1992-03-12 | 1992-09-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-09-11 | 1996-03-12 | 1996-09-11 | $7700.00 | Window Closed / Lapsed |