US5075816A
Expired / Lapsed
US
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Capacitive humidity sensor construction and method for manufacturing the sensor
Assignee: Vaisala Oy
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Filing: 1990-07-18
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Granted: 1991-12-24
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Expires: 2010-07-18
Abstract
Abstract The invention concerns a capacitive humidity sensor (6) capable of being connected to a measurement device of dielectric factor and a method for producing the sensor. The sensor comprises a dielectric layer (3), whose dielectric factor changes according to the moisture content absorbed in the layer, and at least two galvanically isolated conductive layers (2,1) enclosing the dielectric layer (3), where one of the conductive layers (2) of the capacitor construction is provided with a random pattern of clefts (7), which allow an immediate communication of ambient air with the dielectric layer (3). According to the invention, the dielectric layer (3) has a solid structure without cracks corresponding to the clefts (7) of the conductive layer (2). The construction according to the invention offers a reduction of the capillary effect and associated hysteresis up to a complete elimination of the effect in some embodiments of the invention.
Inventors
- 👤 Lars Stormbom
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-10 00:52
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/22; G01N27/223; G01N27/225; Y; Y10; Y10T; Y10T29/00; Y10T29/43; Y10T29/435
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
93 words
A capacitive humidity sensor capable of being connected to a measurement device of dielectric factor, said sensor comprising: a dielectric layer, whose dielectric factor changes in proportion to the moisture content absorbed in the layer; and at least two galvanically isolated conductive layers enclosing the dielectric layer, whereby one of the conductive layers of the capacitor construction is provided with a random pattern of clefts, which allow immediate communication of ambient air with the dielectric layer, the dielectric layer having a solid structure without cracks corresponding to the clefts of the conductive layer.
Claim 2
Dependent Claim
93 words
A capacitive humidity sensor capable of being connected to a measurement device of dielectric factor, said sensor comprising: a dielectric layer, whose dielectric factor changes in proportion to the moisture content absorbed in the layer; and at least two galvanically isolated conductive layers enclosing the dielectric layer, whereby one of the conductive layers of the capacitor construction is provided with a random pattern of clefts, which allow immediate communication of ambient air with the dielectric layer, the dielectric layer having a solid structure without cracks corresponding to the clefts of the conductive layer.
Claim 3
Dependent Claim
37 words
The humidity sensor in accordance with claim 1, wherein the conductive layer with the clefts is covered by a second and dielectric layer which is capable of allowing water vapour to diffuse into the first dielectric layer.
Claim 4
Dependent Claim
30 words
The humidity sensor in accordance with claim 2, wherein the second dielectric layer is firmly adhered both to the conductive electrode layer with the clefts and the first dielectric layer.
Claim 5
Independent Claim
105 words
A method for manufacturing a capacitive humidity sensor, comprising the steps of: producing a first conductive electrode on an insulating substrate; producing a dielectric layer on the first conductive electrode; and forming a second conductive electrode on the dielectric layer from such material with a high resistance to wear that contracts under internal stresses when produced as a thin layer and forms clefts in the second conductive layer, the second conductive electrode being produced on the dielectric layer while the dielectric layer is still in a plasticized state, whereby the clefts formed on the second conductive layer are prevented from extending into the dielectric layer.
Claim 6
Independent Claim
105 words
A method for manufacturing a capacitive humidity sensor, comprising the steps of: producing a first conductive electrode on an insulating substrate; producing a dielectric layer on the first conductive electrode; and forming a second conductive electrode on the dielectric layer from such material with a high resistance to wear that contracts under internal stresses when produced as a thin layer and forms clefts in the second conductive layer, the second conductive electrode being produced on the dielectric layer while the dielectric layer is still in a plasticized state, whereby the clefts formed on the second conductive layer are prevented from extending into the dielectric layer.
Claim 7
Dependent Claim
24 words
The method in accordance with claim 4, wherein the second electrode with the clefts is produced by vacuum evaporation onto the plasticized dielectric layer.
Claim 8
Dependent Claim
22 words
The method in accordance with claim 1, 2, 3, 4 or 5 wherein the dielectric layer is produced from a plastic material.
Claim 9
Dependent Claim
31 words
The method in accordance with claim 4 or 5, wherein the dielectric layer is held in a plasticized state by means of a slowly evaporating solvent such as NMP for instance.
Claim 10
Dependent Claim
58 words
The method in accordance with claim 1, 2, 3, 4 or 5 wherein the dielectric layer is held in a plasticized state with the help of elevated temperature, whereby the sensor is kept at a temperature above the glass transition temperature T g or the melting temperature, e.g., 180° C. during the processing of the second conductive electrode.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1994-12-23 | 1995-06-24 | 1995-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-12-23 | 1999-06-24 | 1999-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-12-23 | 2003-06-24 | 2003-12-24 | $7700.00 | Window Closed / Lapsed |