US3890703A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of making humidity sensor
Assignee: Plessey Inc
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Filing: 1974-02-19
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Granted: 1975-06-24
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Expires: 1994-02-19
Abstract
Abstract The operation of relative humidity sensors made from cobalt oxide on a non-conductive ceramic substrate is improved by heating the sensor for a short period to a high temperature in a reducing atmosphere. This reduces the specific resistance of the device. With a lower resistivity, it is possible to reduce the size of the sensor to the point where it can be included along with a semiconductive device in standard hermetic packages. This makes possible the continuous, on-line monitoring of hermeticity for the life of the circuit without the necessity fo applying a load to the circuit.
Inventors
- 👤 Lawrence E Frazee
- 👤 Anthony V Fraioli
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:52
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/12; G01N27/121; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49099; Y10T29/49101
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
83 words
The method of forming a humidity sensor comprising: mixing cobalt oxide powder with an inert vehicle to form a paste; applying a layer of said paste onto a major surface of a high-temperature resistant dielectric substrate; firing said paste in an oxidizing atmosphere at a temperature of about 1350*C. to 1550*C. to form a hygroscopic element; and firing said hygroscopic element at a temperature of about 1500*C. for a few minutes in a reducing atmosphere, whereby the resistivity of said element is reduced.
Claim 2
Independent Claim
83 words
The method of forming a humidity sensor comprising: mixing cobalt oxide powder with an inert vehicle to form a paste; applying a layer of said paste onto a major surface of a high-temperature resistant dielectric substrate; firing said paste in an oxidizing atmosphere at a temperature of about 1350*C. to 1550*C. to form a hygroscopic element; and firing said hygroscopic element at a temperature of about 1500*C. for a few minutes in a reducing atmosphere, whereby the resistivity of said element is reduced.
Claim 3
Dependent Claim
18 words
The method as claimed in claim 1, and additionally comprising applying a pair of electrodes to said element.
Claim 4
Dependent Claim
13 words
The method as claimed in claim 1, wherein said reducing atmosphere comprises hydrogen.
Claim 5
Dependent Claim
59 words
IN THE METHOD OF PRODUCING A HUMIDITY SENSOR BY FIRING A LAYER OF A COBALT OXIDE PASTE ONTO A HIGH-TEMPERATURE RESISTANT, DIELECTRIC SUBSTRATE TO PRODUCE A HYGROSCOPIC ELEMENT; THE IMPROVEMENT COMPRISING FIRING SAID ELEMMENT A SECOND TIME FOR A SHORT PERIOD AT A TEMPERATURE OF ABOUT 1500*C. IN A REDUCING ATMOSPHERE, WHEREBY THE RESISTIVITY OF SAID ELENENT IS LOWERED.
Claim 6
Dependent Claim
59 words
IN THE METHOD OF PRODUCING A HUMIDITY SENSOR BY FIRING A LAYER OF A COBALT OXIDE PASTE ONTO A HIGH-TEMPERATURE RESISTANT, DIELECTRIC SUBSTRATE TO PRODUCE A HYGROSCOPIC ELEMENT; THE IMPROVEMENT COMPRISING FIRING SAID ELEMMENT A SECOND TIME FOR A SHORT PERIOD AT A TEMPERATURE OF ABOUT 1500*C. IN A REDUCING ATMOSPHERE, WHEREBY THE RESISTIVITY OF SAID ELENENT IS LOWERED.
Claim 7
Dependent Claim
13 words
The method as claimed in claim 4, wherein said reducing atmosphere is hydrogen.
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) | 1978-06-23 | 1978-12-23 | 1979-06-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-23 | 1982-12-23 | 1983-06-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-23 | 1986-12-23 | 1987-06-24 | $7700.00 | Window Closed / Lapsed |