US4288742A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrical moisture sensor
Assignee: Dartmouth College
•
Filing: 1979-12-18
•
Granted: 1981-09-08
•
Expires: 1999-12-18
Abstract
Abstract A moisture sensor including a probe formed with a first ring of spines extending in parallel outward from a base and a second ring of spines extending in parallel outward from the base separated and insulated from the first ring, the spines forming an effective coaxial capacitor and being insertable into material to be sensed and an RC bridge circuit, preferably a Wien bridge connected to the rings to measure the impedance of the material.
Inventors
- 👤 John E. Walsh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 15:32
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/26; G01N; G01N27/00; G01N27/02; G01N27/22; G01N27/223
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
91 words
A moisture sensor comprising: a base, a first ring of spines extending outwardly from said base in parallel; a second ring of spines extending outwardly from said base in parallel within said first ring, separated and electrically insulated therefrom, said spines being sufficient in number to appear as a ground plane forming an effective coaxial capacitor and being insertable into material to be sensed; and circuit means connected to said first and second rings for applying an ac signal to said spines measuring the impedance of said material between said rings.
Claim 2
Dependent Claim
91 words
A moisture sensor comprising: a base, a first ring of spines extending outwardly from said base in parallel; a second ring of spines extending outwardly from said base in parallel within said first ring, separated and electrically insulated therefrom, said spines being sufficient in number to appear as a ground plane forming an effective coaxial capacitor and being insertable into material to be sensed; and circuit means connected to said first and second rings for applying an ac signal to said spines measuring the impedance of said material between said rings.
Claim 3
Dependent Claim
147 words
A moisture sensor comprising: a probe having a base, a first ring of spines extending outwardly from said base in parallel, a second ring of spines extending outwardly from said base in parallel within said first ring, means electrically insulating said first ring from said second ring, said rings being sufficient in number to appear as a ground plane forming an effective coaxial capacitor and being insertable into material to be sensed; circuit means including an RC bridge with a resistor and capacitor connected to said first and second rings for applying an ac signal to said spines to form a bridge with the resistance and capacitance of said material between said rings, for producing electrical signals indicating the impedance of said materials; means for producing a variable frequency signal and applying said signal to said bridge; and meter means connected to said bridge for indicating voltage.
Claim 4
Dependent Claim
147 words
A moisture sensor comprising: a probe having a base, a first ring of spines extending outwardly from said base in parallel, a second ring of spines extending outwardly from said base in parallel within said first ring, means electrically insulating said first ring from said second ring, said rings being sufficient in number to appear as a ground plane forming an effective coaxial capacitor and being insertable into material to be sensed; circuit means including an RC bridge with a resistor and capacitor connected to said first and second rings for applying an ac signal to said spines to form a bridge with the resistance and capacitance of said material between said rings, for producing electrical signals indicating the impedance of said materials; means for producing a variable frequency signal and applying said signal to said bridge; and meter means connected to said bridge for indicating voltage.
Claim 5
Dependent Claim
28 words
A sensor as in claim 1 or 2 wherein said circuit means is mounted on said base on the side opposite the side from which said spines extend.
Claim 6
Dependent Claim
14 words
A sensor as in claim 1 or 2 wherein said spines are stainless steel.
References Cited (Backward Citations)
US2587771A
Cited
GB709177A
Cited
US2870404A
Cited
US2975361A
Cited
US3803570A
Cited
US3882381A
Cited
US3986110A
Cited
US4135151A
Cited
JPS54115296A
Cited
US4174498A
Cited
US4181881A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-09-07 | 1985-03-09 | 1985-09-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-09-07 | 1989-03-09 | 1989-09-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-09-07 | 1993-03-09 | 1993-09-08 | $7700.00 | Window Closed / Lapsed |