US3821641A
Expired / Lapsed
US
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Resistance level detector
Assignee: ECOS ELECTRONICS CORP
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Filing: 1972-12-12
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Granted: 1974-06-28
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Expires: 1992-12-12
Abstract
Abstract A portable resistance level detector for determining the unknown resistance between a pair of test points under high voltage and low voltage test conditions is disclosed. More particularly, the detector includes a switching arrangement for selectively coupling regulated high-level and low-level DC potentials across the test points and a resistive threshold arrangement for sampling the resultant current to determine whether the unknown resistance is below certain preselected thresholds. If the resistance is below any of the thresholds set for high-level and low-level testing, an audio system is enabled to generate a particular audible tone associated with each threshold. A meter is also provided to provide an exact read-out of the resistance measured under high voltage test conditions. The high-level DC test voltage is, in turn, developed by a novel regulated voltage generator. The generator includes circuitry for developing a pulse train at a rate determined by the charging and discharging time constants of a capacitive element included in a control circuit. The pulses are subsequently rectified and filtered to provide a DC potential. A feedback network monitors the DC output potential to vary the charging time constant and hence the rate at which pulses are applied to the rectification network. In this manner, the DC potential is maintained at a constant level regardless of load conditions.
Inventors
- 👤 P Portoulas
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 08:06
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/025
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
167 words
A resistance level detector for measuring the unknown resistance between first and second test points under low voltage and high voltage test conditions, said detector comprising in combination: generator means for developing voltage-stabilized high-level and low-level DC potentials; switch means interconnecting said generator means and said unknown resistance for selectively applying either of said voltage stabilized DC potentials to said resistance; threshold means coupled to said unknown resistance for establishing preselected resistive threshold levels, by monitoring the current conducted through said unknown resistance during low voltage and high voltage testing to determine whether said unknown resistance is below any of said preselected thresholds; audio means activated by said threshold means for generating a tone associated with a particular one of said preselected thresholds when said threshold means determines that said unknown resistance is below said particular threshold; and meter means coupled to said unknown resistance for measuring the current conducted through said unknown resistance during high voltage testing to provide an accurate determination of said unknown resistance.
Claim 2
Dependent Claim
167 words
A resistance level detector for measuring the unknown resistance between first and second test points under low voltage and high voltage test conditions, said detector comprising in combination: generator means for developing voltage-stabilized high-level and low-level DC potentials; switch means interconnecting said generator means and said unknown resistance for selectively applying either of said voltage stabilized DC potentials to said resistance; threshold means coupled to said unknown resistance for establishing preselected resistive threshold levels, by monitoring the current conducted through said unknown resistance during low voltage and high voltage testing to determine whether said unknown resistance is below any of said preselected thresholds; audio means activated by said threshold means for generating a tone associated with a particular one of said preselected thresholds when said threshold means determines that said unknown resistance is below said particular threshold; and meter means coupled to said unknown resistance for measuring the current conducted through said unknown resistance during high voltage testing to provide an accurate determination of said unknown resistance.
Claim 3
Dependent Claim
40 words
A resistance level detector in accordance with claim 1 including supply means comprising a battery for providing an operating potential to said generator means, said operating potential enabling said generator means to develop said voltage-stabilized high-level and low-level DC potentials.
Claim 4
Dependent Claim
56 words
A resistance level detector in accordance with claim 2 wherein said switch means couples said meter means to said supply means during low voltage testing, said meter means monitoring the current from said supply means for providing a visual indication of the charged condition of said battery to insure that said generator means is properly functioning.
Claim 5
Dependent Claim
90 words
A resistance level detector in accordance with claim 1 wherein said threshold means includes means for establishing a first selectable threshold during low voltage testing and enabling said audio means to generate an interrupted tone whenever said unknown resistance is below said first threshold, said threshold means also establishing second and third selectable thresholds during high voltage testing and enabling said audio means to generate an interrupted tone when said unknown resistance is below said second threshold and a steady tone when said unknown resistance is below said third threshold.
Claim 6
Dependent Claim
45 words
A resistance level detector in accordance with claim 4 including oscillator means and steady tone means for driving said audio means, said audio means generating an interrupted signal when said oscillator means are enabled and a steady tone responsive to steady tone means being enabled.
Claim 7
Dependent Claim
93 words
A resistance level detector in accordance with claim 5 wherein said means for establishing said first threshold includes first variable impedance means and first amplifier means, said first variable impedance means being serially connected with said unknown resistance between said first test point and a plane of a reference potential during low voltage testing, said first variable impedance being adjusted to bias said first amplifier means to conduction whenever said unknown resistance is below said first threshold, said first amplifier means enabling said oscillator so that said audio means generates an interrupted tone.
Claim 8
Dependent Claim
93 words
A resistance level detector in accordance with claim 5 wherein said means for establishing said second threshold includes second variable impedance means and second amplifier means, said second variable impedance means being serially connected with said unknown resistance between said first test point and a plane of reference potential during high voltage testing, said second variable impedance being adjusted to bias said second amplifier means to conduction whenever said unknown resistance is below said second threshold, said secoNd amplifier means enabling said oscillator means so that said audio means generates an interrupted tone.
Claim 9
Dependent Claim
113 words
A resistance level detector in accordance with claim 5 wherein said means for establishing said third threshold includes third variable impedance means and third amplifier means, said third variable impedance means being serially connected with said unknown resistance between said first test point and a plane of reference potential during high voltage testing, said third variable impedance means being adjusted to bias said third amplifier means to conduction whenever said unknown resistance is below said third threshold, said third amplifier means applying a control signal to said generating means to reduce said high-level DC potential to an intermediate level enabling said steady tone means so that said audio means generates a steady tone.
Claim 10
Dependent Claim
64 words
A resistance level detector in accordance with claim 8 wherein said steady tone means comprises amplifier means, said amplifier means being switched from conduction to non-conduction whenever said high-level DC potential is reduced to said intermediate level, said amplifier means developing an increased output voltage for driving said audio means to generate a steady tone when said unknown resistance falls below said third threshold.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-27 | 1977-12-27 | 1978-06-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-27 | 1981-12-27 | 1982-06-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-27 | 1985-12-27 | 1986-06-28 | $7700.00 | Window Closed / Lapsed |