US3774110A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Static electric field detector
Assignee: Woodhead Inc
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Filing: 1971-11-05
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Granted: 1973-11-20
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Expires: 1991-11-05
Abstract
Abstract This apparatus is used to detect the presence of static or alternating electric fields. The electric field intensity is sensed with a probe by proximity capacitance coupling. It comprises an antenna which applies any signal it detects to the input of an amplifier. The output of the amplifier is applied to the input of a threshold circuit which conducts when an input signal of greater than a prescribed value is detected. Conduction of the threshold circuit energizes an oscillator which drives indicators of various types. Once a prescribed threshold level is exceeded, display is activated. Hence, the device of this invention provides a go-no-go presentation of field intensities.
Inventors
- 👤 D Roveti
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 18:40
CPC Classifications
G; G01; G01R; G01R29/00; G01R29/24; G01R5/00; G01R5/28
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
338 words
A portable detector of electrical fields comprising a single antenna adapted to have a voltage induced therein by a changing electrical field, a normally conductive first electronic switch having a first main conductive path and a first control electrode, a first resistor for connecting one end of said antenna to said first control electrode, a multiposition switch having a common contact connected to ground, a second resistor connected to said one end of said antenna and to one contact of said switch, means for directly connecting said one end of said antenna to another contact of said switch so that when said common contact touches said one contact the antenna is connected to ground through said second resistor and when said common contact touches said other contact said antenna is directly connected to ground, a first normally nonconductive transistor having a second control electrode, means for connecting said second control electrode to said first main conductive path, said first main conduction path becoming nonconductive when said common contact touches said other contact and a voltage is induced in said antenna by a changing electrical field and said first transistor becoming conductive when said first main conduction path becomes nonconductive, a second normally nonconductive electronic switch having a third control electrode and a second main conductive path, a source of electrical energy, an oscillator, a power amplifier connected to the output of said oscillator, means for connecting said second main conduction path in series between said source of electrical energy and said oscillator and power amplifier so that said oscillator and said power amplifier are not energized by said source of electrical energy unless said second electronic switch is conductive, means for connecting said third control electrode to said first transistor so that when said first transistor becomes conductive it renders said second electronic switch conductive, and a signalling device connected to the output of said power amplifier to be energized thereby whenever the antenna enters an electrical field of sufficient strength to render said first electronic switch nonconductive.
Claim 2
Dependent Claim
338 words
A portable detector of electrical fields comprising a single antenna adapted to have a voltage induced therein by a changing electrical field, a normally conductive first electronic switch having a first main conductive path and a first control electrode, a first resistor for connecting one end of said antenna to said first control electrode, a multiposition switch having a common contact connected to ground, a second resistor connected to said one end of said antenna and to one contact of said switch, means for directly connecting said one end of said antenna to another contact of said switch so that when said common contact touches said one contact the antenna is connected to ground through said second resistor and when said common contact touches said other contact said antenna is directly connected to ground, a first normally nonconductive transistor having a second control electrode, means for connecting said second control electrode to said first main conductive path, said first main conduction path becoming nonconductive when said common contact touches said other contact and a voltage is induced in said antenna by a changing electrical field and said first transistor becoming conductive when said first main conduction path becomes nonconductive, a second normally nonconductive electronic switch having a third control electrode and a second main conductive path, a source of electrical energy, an oscillator, a power amplifier connected to the output of said oscillator, means for connecting said second main conduction path in series between said source of electrical energy and said oscillator and power amplifier so that said oscillator and said power amplifier are not energized by said source of electrical energy unless said second electronic switch is conductive, means for connecting said third control electrode to said first transistor so that when said first transistor becomes conductive it renders said second electronic switch conductive, and a signalling device connected to the output of said power amplifier to be energized thereby whenever the antenna enters an electrical field of sufficient strength to render said first electronic switch nonconductive.
Claim 3
Dependent Claim
62 words
The detector defined in claim 1 wherein said oscillator comprises two separate oscillating circuits having two different frequencies of oscillation, means for connecting said two oscillating circuits in parallel to said second main conduction path so that both oscillating circuits are energized at the same time, and meanS for connecting the outputs of said two oscillating circuits together to said power amplifier.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-11-19 | 1977-05-21 | 1977-11-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-19 | 1981-05-21 | 1981-11-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-19 | 1985-05-21 | 1985-11-20 | $7700.00 | Window Closed / Lapsed |