US3710244A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Capacitance probe for detecting moisture with very long cables
Assignee: Individual
•
Filing: 1971-01-11
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Granted: 1973-01-09
•
Expires: 1991-01-11
Abstract
Abstract A probe consists of two spaced elements, each consisting of a piece of foil, sheet, rod or tube, each insulated from the other and from the material whose moisture is to be measured. The elements are connected by two coaxial or one tri-axial cable to a remote piece of electronic equipment including an ultrasonic oscillator which transmits signals to the probes, which thus function as a variable capacitor, the variation being dependent on the moisture content of the said material in which the probes are imbedded. The equipment has a preamplifier (integrated circuit charge amplifier) having high frequency response and very low voltage differential between the two inputs. An integrated circuit peak detector provides a positive D.C. voltage proportional to the input peak voltage from the preamplifier. Such D.C. voltage may be measured by a microammeter to indicate moisture, or the output may be used to control a valve (for irrigation, e.g.) Several probes and valves may be used in an irrigation system, or the like.
Inventors
- 👤 G Rauchwerger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:34
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/22; G01N27/223
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
153 words
Probe means for sensing moisture in a solid or liquid medium by measuring capacitance between and across a first and a second conductive medium comprising a non-conductive, moisture-proof thin plastic sheet base, a first and a second strip of metallic foil separated from each other, a pair of electric lead wires having bare ends, thin metal foil means electrically connecting the bare end of one wire to one strip and the other bare end to the other strip, and a pair of plastic sheets on opposite sides of said probe means securing said strips to said base and insulating said strips from each other and from the exterior of said probe, said sheets comprising homogeneous plastic material completely surrounding said foil means, sheet base and bare ends of wire, said sheets laminated together and hermetically sealing said wires to said probe and insulating said wires and foil from said soil or liquid medium.
Claim 2
Dependent Claim
153 words
Probe means for sensing moisture in a solid or liquid medium by measuring capacitance between and across a first and a second conductive medium comprising a non-conductive, moisture-proof thin plastic sheet base, a first and a second strip of metallic foil separated from each other, a pair of electric lead wires having bare ends, thin metal foil means electrically connecting the bare end of one wire to one strip and the other bare end to the other strip, and a pair of plastic sheets on opposite sides of said probe means securing said strips to said base and insulating said strips from each other and from the exterior of said probe, said sheets comprising homogeneous plastic material completely surrounding said foil means, sheet base and bare ends of wire, said sheets laminated together and hermetically sealing said wires to said probe and insulating said wires and foil from said soil or liquid medium.
Claim 3
Dependent Claim
56 words
Probe means according to claim 1 which further comprises an elongated cable having two conductors and grounding means grounding the space between conductors to eliminate capacitance between said conductors, said cable comprising a triaxial cable, the central and outer conductor of said cable connected to said first and second foil and the middle conductor to ground.
Claim 4
Dependent Claim
37 words
Probe means according to claim 1 which further comprises elongated first and second coaxial cables, each having its outer conductor grounded and one of said lead wires connected to the central conductor of each said coaxial cable.
Claim 5
Dependent Claim
40 words
A probe according to claim 1 in which both said plastic sheets are formed of a material severable along a line between said strips to form two probes, movable relative to each other and each connected to a lead wire.
Claim 6
Dependent Claim
34 words
Probe means according to claim 1 in which said base is a cylinder and said strips are on opposite sides of the outside of said cylinder arranged parallel to the axis of said cylinder.
Claim 7
Dependent Claim
101 words
In combiNation, probe means according to claim 3 with said probe means imbedded directly in said medium, an oscillator having its output connected to one said cable, a positive peak detector having its input connected to the other said conductor, said detector emitting a positive D.C. voltage proportional to capacitance between said strips and a comparator receiving the output of said detector and comparing said output with an adjustable reference voltage and having a switch opened and closed depending on whether the capacitance between said foils is more or less than a predetermined value as set by said adjustable reference voltage.
Claim 8
Dependent Claim
84 words
The combination according to claim 6 which further comprises an amplifier between said other conductor and said detector and a feedback capacitor across said amplifier having a characteristic such that the input voltage sent into one said cable by said oscillator equals the output voltage of said amplifier when said feedback capacitor equals the capacitance of said probe in the material under test and wherein the output voltage of said amplifier varies inversely to the ratio of the feedback capacitor to the probe capacitor.
References Cited (Backward Citations)
SU160355A1
Cited
US2285152A
Cited
US2373846A
Cited
US2555977A
Cited
US2754478A
Cited
GB701862A
Cited
GB925656A
Cited
US3022499A
Cited
US3043993A
Cited
US3341774A
Cited
US3421077A
Cited
US3519922A
Cited
US3515987A
Cited
US3523243A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-01-09 | 1976-07-10 | 1977-01-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-09 | 1980-07-10 | 1981-01-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-09 | 1984-07-10 | 1985-01-09 | $7700.00 | Window Closed / Lapsed |