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US3582728A
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Capacitance humidity sensing element
Assignee: Johnson Controls International Inc
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Filing: 1969-03-06
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Granted: 1971-06-01
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Expires: 1989-03-06
Abstract
Abstract A capacitance synthetic humidity sensing element comprising a moisture sensitive dielectric core and having electrode layers integrally bonded to opposite surfaces of the core. Each electrode layer consists of a matrix of a dielectric, moisturepermeable material, and a plurality of interconnected electrically conductive particles are dispersed within the matrix. The element is supported within a central opening of a frame, and the frame includes an electrically conductive section which is in electrical contact with the electrode layers. At least one of the electrode layers is exposed completely to the environment being sensed. Changes in relative humidity provide changes in capacitance and this can be converted into a signal to indicate the relative humidity or to operate a humidity control system.
Inventors
- 👤 Paul E Thoma
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 04:59
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/22; G01N27/223; G01N27/225
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
90 words
A capacitance synthetic humidity sensing element, comprising a sheetlike core formed of a dielectric moisture sensitive material, a dielectric outer layer bonded to each surface of the core and being porous to the diffusion of water vapor therethrough, and a plurality of interconnected electrically conductive particles distributed within each outer layer the electrically conductive particles of each outer layer adapted to be connected in an electrical circuit, water vapor from the atmosphere penetrating said outer layers and being absorbed in said core to thereby vary the capacitance of the element.
Claim 2
Dependent Claim
90 words
A capacitance synthetic humidity sensing element, comprising a sheetlike core formed of a dielectric moisture sensitive material, a dielectric outer layer bonded to each surface of the core and being porous to the diffusion of water vapor therethrough, and a plurality of interconnected electrically conductive particles distributed within each outer layer the electrically conductive particles of each outer layer adapted to be connected in an electrical circuit, water vapor from the atmosphere penetrating said outer layers and being absorbed in said core to thereby vary the capacitance of the element.
Claim 3
Dependent Claim
41 words
The humidity sensing element of claim 1, wherein said core is capable of absorbing at least 1 percent, based on its dry weight, of moisture when exposed to 95 percent relative humidity at 70* F. for a period of 30 minutes.
Claim 4
Dependent Claim
15 words
The humidity sensing element of claim 1, wherein said electrically conductive particles comprise graphitized carbon.
Claim 5
Dependent Claim
20 words
The humidity sensing element of claim 1, wherein both the core and the outer layers are formed of organic materials.
Claim 6
Dependent Claim
20 words
The humidity sensing element of claim 4, wherein both the core and the outer layers are formed of cellulose esters.
Claim 7
Dependent Claim
37 words
The humidity sensing element of claim 1, wherein said element has 0.1 percent to 2.0 percent capacitance change with a 1 percent change in relative humidity at temperatures in the range of 40* F. to 200* F.
Claim 8
Dependent Claim
39 words
The humidity sensing element of claim 1, wherein at least one of said outer layers is formed of a cellulose ester, and said element includes a hydrolyzed film of cellulose disposed on the outer surface of said outer layer.
Claim 9
Dependent Claim
111 words
A humidity sensing assembly, comprising an electrically insulating frame having an opening therein, and a capacitance syNthetic humidity sensing element extending across said opening, said element comprising a sheetlike core formed of a dielectric material having a relatively high sensitivity to moisture, and said element including an electrode layer bonded to each surface of the core, each electrode layer including a moisture permeable dielectric matrix and having a plurality of interconnected electrically conductive particles dispersed within the matrix, a first of said electrode layers extending solely within the opening of the frame, means for attaching the element to said frame, and means for connecting the electrode layers in an electric circuit.
Claim 10
Dependent Claim
111 words
A humidity sensing assembly, comprising an electrically insulating frame having an opening therein, and a capacitance syNthetic humidity sensing element extending across said opening, said element comprising a sheetlike core formed of a dielectric material having a relatively high sensitivity to moisture, and said element including an electrode layer bonded to each surface of the core, each electrode layer including a moisture permeable dielectric matrix and having a plurality of interconnected electrically conductive particles dispersed within the matrix, a first of said electrode layers extending solely within the opening of the frame, means for attaching the element to said frame, and means for connecting the electrode layers in an electric circuit.
Claim 11
Dependent Claim
18 words
The assembly of claim 8, wherein said frame is generally annular in shape and has a central opening.
Claim 12
Dependent Claim
22 words
The assembly of claim 9, wherein the periphery of said first electrode layer terminates adjacent the inner surface of said annular frame.
Claim 13
Dependent Claim
35 words
The assembly of claim 9, including a pair of electrically conductive rings disposed on the inner surface of said frame, the electrically conductive particles of each electrode layer being connected to one of said rings.
Claim 14
Dependent Claim
24 words
The assembly of claim 11, and including a coating of an electrically conductive material connecting each ring to the particles of the electrode layers.
Claim 15
Dependent Claim
37 words
The assembly of claim 8, wherein said particles are graphitized carbon capable of adsorbing and/or absorbing less than 4 percent by weight of water at 78* F. with relative humidity changes from 0 percent to 90 percent.
Claim 16
Dependent Claim
34 words
The assembly of claim 8, wherein both the core and the matrix having a dielectric constant in the range of 1.1 to 10 and a high electric resistivity above 1 X 109 ohm inches.
Claim 17
Dependent Claim
39 words
The assembly of claim 8, wherein said core is capable of absorbing at least 1 percent, based on its dry weight, of moisture when exposed to 85 percent relative humidity at 70* F. for a period of 30 minutes.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-05-31 | 1974-11-30 | 1975-06-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-05-31 | 1978-11-30 | 1979-06-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-05-31 | 1982-11-30 | 1983-06-01 | $7700.00 | Window Closed / Lapsed |