US3673589A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Intruder detector
Assignee: CURRENT IND Inc
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Filing: 1969-05-05
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Granted: 1972-06-27
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Expires: 1989-05-05
Abstract
Abstract A probe is located to carry electric currents brought about by change in the surrounding electrostatic field to produce a signal feeding a high input impedance circuit connected to an operational amplifier connected in the feedback mode to produce an output signal indicative of the presence of an object in the vicinity of the probe which disturbs the electrostatic field. The latter signal is used to feed a monitoring circuit which indicates that the device is operational and an alarm circuit which may be selectively activated.
Inventors
- 👤 Robert W Barrett
- 👤 Pat S Preese
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 17:25
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/08; G01V3/088
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
202 words
An intruder detection device comprising, in combination: a. a probe located in an electrostatic field which has a minute conduction current flow in its quiescent state, said probe arranged to sense and carry displacement current resulting from change in the quiescent state of said electrostatic field; b. Conducting means connected to said probe for carrying the displacement current carried by said probe; c. ultra high impedance means coupled to said conducting means for developing a signal proportional to the displacement current carried by said conducting means; d. a differential input operational amplifier for producing an amplified output signal; e. means coupling said ultra high impedance means to the input of said operational amplifier for feeding at least part of said developed signal as an input thereto; f. indicator circuit means coupled to the output of said operational amplifier for producing visual indications of the signals developed by said operational amplifier to show that said operational amplifier is operative; g. alarm circuit means coupled to the output of said operational amplifier for producing an alarm signal in response to the signals developed by said operational amplifier; and h. control means connected to said alarm circuit means for selectively disabling or enabling the latter.
Claim 2
Dependent Claim
202 words
An intruder detection device comprising, in combination: a. a probe located in an electrostatic field which has a minute conduction current flow in its quiescent state, said probe arranged to sense and carry displacement current resulting from change in the quiescent state of said electrostatic field; b. Conducting means connected to said probe for carrying the displacement current carried by said probe; c. ultra high impedance means coupled to said conducting means for developing a signal proportional to the displacement current carried by said conducting means; d. a differential input operational amplifier for producing an amplified output signal; e. means coupling said ultra high impedance means to the input of said operational amplifier for feeding at least part of said developed signal as an input thereto; f. indicator circuit means coupled to the output of said operational amplifier for producing visual indications of the signals developed by said operational amplifier to show that said operational amplifier is operative; g. alarm circuit means coupled to the output of said operational amplifier for producing an alarm signal in response to the signals developed by said operational amplifier; and h. control means connected to said alarm circuit means for selectively disabling or enabling the latter.
Claim 3
Dependent Claim
60 words
The invention as set forth in claim 1 further including: e. full-wave rectifying means connected to the output of said amplifier for producing a dc signal proportional to the amplifier output; and f. means connected to said rectifying means for feeding at least a portion of said dc signal to said indicator circuit means and to said alarm circuit means.
Claim 4
Dependent Claim
141 words
An intruder detection device, comprising in combination: a. an electrically conductive probe located in an electrostatic field in air which has a minute conduction current flow in its quiescent state, said probe arranged to sense and carry displacement current resulting from change in the quiescent state of said electrostatic field; b. ultra high impedance input means coupled to said probe for developing a signal in response to the displacement current carried by said probe; c. a differential-input operational amplifier; d. means connected to said ultra high impedance means for feeding at least part of said developed signal into the input of said operational amplifier; e. rectifying circuit means connected to the output of the operational amplifier for producing a dc signal representation of said output; and f. means for feeding at least part of said dc signal to an alarm circuit.
Claim 5
Dependent Claim
141 words
An intruder detection device, comprising in combination: a. an electrically conductive probe located in an electrostatic field in air which has a minute conduction current flow in its quiescent state, said probe arranged to sense and carry displacement current resulting from change in the quiescent state of said electrostatic field; b. ultra high impedance input means coupled to said probe for developing a signal in response to the displacement current carried by said probe; c. a differential-input operational amplifier; d. means connected to said ultra high impedance means for feeding at least part of said developed signal into the input of said operational amplifier; e. rectifying circuit means connected to the output of the operational amplifier for producing a dc signal representation of said output; and f. means for feeding at least part of said dc signal to an alarm circuit.
Claim 6
Dependent Claim
29 words
The invention as set forth in claim 3 including means for providing a negative feedback signal from the output of said operational amplifier to said high impedance input means.
Claim 7
Dependent Claim
105 words
The invention as set forth in claim 4 wherein said ultra high impedance input means comprises: ultra large value resistance means attached electrically in series with the sensor for producing a signal proportional to the current carried by said sensor; a field effect transistor; means for connecting the gate control element of the field effect transistor to said resistance means; a low valued resistance means connected in series with the current-carrying elements of said field effect transistor for producing a signal proportional to the current passing through the transistor; and means for connecting said latter resistance means to a signal input of said operational amplifier.
Claim 8
Dependent Claim
56 words
The invention as set forth in claim 5 including: a dc voltage divider network; means for selectively tapping off different dc signal levels from said divider network; and means for connecting said tap means to a second input of said operational amplifier whereby the differential signal input to said amplifier can be adjusted for quiescent conditions.
Claim 9
Dependent Claim
93 words
The invention as set forth in claim 5 wherein said ultra large value resistance means comprises: a first high value resistor; a second resistor having a value in the order of 10 times that of said first resistor, said second resistor being attached at one end to one end of the first resistor and at its other end to the output of said operational amplifier for providing a negative feedback path; and conducting means connecting the gate controL element of the field effect transistor to the junction of said first and second resistors.
Claim 10
Dependent Claim
22 words
The invention as set forth in claim 7 further including capacitor means attached across said second resistor for providing high frequency filtering.
Claim 11
Dependent Claim
122 words
An intruder detection device, comprising, in combination: a. an electrostatic field having a substantially steady, non-varying, potential gradient in its quiescent state; b. a probe located in said electrostatic field arranged to sense and to carry displacement current resulting from a change in the potential gradient of the field brought about by a charged or uncharged body disturbing the quiescent state; c. means coupled to said probe for producing an output signal in response to said displacement current; d. means for preventing said output signal producing means from producing an output signal when the rate of change of the displacement current is above or below a predetermined frequency range; and e. means responsive to said output signal for producing an alarm signal.
Claim 12
Dependent Claim
122 words
An intruder detection device, comprising, in combination: a. an electrostatic field having a substantially steady, non-varying, potential gradient in its quiescent state; b. a probe located in said electrostatic field arranged to sense and to carry displacement current resulting from a change in the potential gradient of the field brought about by a charged or uncharged body disturbing the quiescent state; c. means coupled to said probe for producing an output signal in response to said displacement current; d. means for preventing said output signal producing means from producing an output signal when the rate of change of the displacement current is above or below a predetermined frequency range; and e. means responsive to said output signal for producing an alarm signal.
Claim 13
Dependent Claim
22 words
The invention as set forth in claim 9 wherein said means for producing an output signal includes a differential input operational amplifier.
References Cited (Backward Citations)
US3258762A
Cited
US2802178A
Cited
US3201775A
Cited
US3346856A
Cited
US3564529A
Cited
US3493954A
Cited
US3452346A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-06-27 | 1975-12-27 | 1976-06-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-27 | 1979-12-27 | 1980-06-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-27 | 1983-12-27 | 1984-06-27 | $7700.00 | Window Closed / Lapsed |