US4751466A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Instrument for on-line measurement of the absolute electrical conductivity of a liquid
Assignee: Ford Global Technologies LLC
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Filing: 1987-01-20
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Granted: 1988-06-14
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Expires: 2007-01-20
Abstract
Abstract The invention is directed to an instrument for measuring the absolute electrical conductivity of liquids, which instrument may be employed on-line in a recirculating paint bath to measure the conductivity of the paint. The instrument comprises a four electrode probe and a meter which comprises a device for generating and controlling an AC current connected to the first electrode such that a constant AC voltage is maintained across the second and fourth electrodes and a device for measuring and detecting an AC current connected to the third electrode, wherein the fourth electrode is maintained at the same potential as a nearby ground.
Inventors
- 👤 Alex D. Colvin
- 👤 James W. Butler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 11:38
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/06; G01N27/07; G01N33/00; G01N33/26; G01N33/32
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
133 words
An instrument for measuring of the absolute electrical conductivity of a liquid, said instrument comprising: a probe comprising an electrically insulating tube and four electrodes within said tube, said electrodes being spaced substantially parallel to each other and substantially perpendicular to the longitudinal axis of said tube so as to form a second and third electrode between a first and fourth electrode, said tube having a substantially uniform cross-sectional area at least between said second and third electrodes; and a meter comprising: means for generating and controlling an AC current connected to said first electrode such that a constant AC voltage is maintained across said second and said fourth electrodes; and means for measuring and detecting an AC current connected to said third electrode; wherein said fourth electrode is maintained at ground potential.
Claim 2
Dependent Claim
133 words
An instrument for measuring of the absolute electrical conductivity of a liquid, said instrument comprising: a probe comprising an electrically insulating tube and four electrodes within said tube, said electrodes being spaced substantially parallel to each other and substantially perpendicular to the longitudinal axis of said tube so as to form a second and third electrode between a first and fourth electrode, said tube having a substantially uniform cross-sectional area at least between said second and third electrodes; and a meter comprising: means for generating and controlling an AC current connected to said first electrode such that a constant AC voltage is maintained across said second and said fourth electrodes; and means for measuring and detecting an AC current connected to said third electrode; wherein said fourth electrode is maintained at ground potential.
Claim 3
Dependent Claim
26 words
An instrument according to claim 1, wherein the measuring and detecting means connected to said third electrode comprises a synchronous detection means for measuring the current.
Claim 4
Dependent Claim
25 words
An instrument according to claim 2, wherein said synchronous detection means comprises a field effect transistor switch which is driven by a square wave oscillator.
Claim 5
Dependent Claim
22 words
An instrument according to claim 1, wherein said generating and controlling means connected to said first electrode generates a square wave voltage.
Claim 6
Dependent Claim
20 words
An instrument according to claim 1, wherein said electrodes are spaced at least one tube diameter apart from one another.
Claim 7
Dependent Claim
21 words
An instrument according to claim 1, wherein said constant AC voltage is a voltage of about 1.5 volts peak to peak.
References Cited (Backward Citations)
US2871445A
Cited
US2599413A
Cited
US3376501A
Cited
US3582767A
Cited
US3924175A
Cited
US3993945A
Cited
US4118663A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-06-14 | 1991-12-14 | 1992-06-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-06-14 | 1995-12-14 | 1996-06-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-06-14 | 1999-12-14 | 2000-06-14 | $7700.00 | Window Closed / Lapsed |