US3906426A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Humidity sensor
Assignee: Plessey Inc
•
Filing: 1974-10-31
•
Granted: 1975-09-16
•
Expires: 1994-10-31
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 semiconductor device in standard hermetic packages. This makes possible the continuous, on-line monitoring of hermeticity for the lift of the circuit without the necessity of 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
2026-11-07 15:02
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; Y10T29/49101
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
61 words
A HUMIDITY SENSOR COMPRISING: A HIGH-TEMPERATURE RESISTANT, DIELECTRIC SUBSTRATE, A DOUBLE-FIRED LAYER OF COBALT OXIDE ON A MAJOR SURFACE OF SAID SUBSTRATE, SAID DOUBLE-FIRED LAYER HAVING A LOWER THAN NORMAL RESISTIVITY AS A RESULT OF A SECOND FIRING IN A REDUCING ATMOSPHERE AT ABOUT 1500*C FOR A BRIEF PERIOD, AND A FIRED-ON PAIR OF ELECTRODES IN CONTACT WITH SAID DOUBLEFIRED LAYER.
Claim 2
Dependent Claim
61 words
A HUMIDITY SENSOR COMPRISING: A HIGH-TEMPERATURE RESISTANT, DIELECTRIC SUBSTRATE, A DOUBLE-FIRED LAYER OF COBALT OXIDE ON A MAJOR SURFACE OF SAID SUBSTRATE, SAID DOUBLE-FIRED LAYER HAVING A LOWER THAN NORMAL RESISTIVITY AS A RESULT OF A SECOND FIRING IN A REDUCING ATMOSPHERE AT ABOUT 1500*C FOR A BRIEF PERIOD, AND A FIRED-ON PAIR OF ELECTRODES IN CONTACT WITH SAID DOUBLEFIRED LAYER.
Claim 3
Dependent Claim
30 words
The humidity sensor as claimed in claim 1, wherein the resistivity of said double-fired layer is at least one order of magnitude less as a result of said second firing.
Claim 4
Dependent Claim
19 words
The humidity sensor as claimed in claim 1, wherein said electrodes are in the form of closely-spaced, interdigitated fingers.
References Cited (Backward Citations)
US3345596A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-15 | 1979-03-17 | 1979-09-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-15 | 1983-03-17 | 1983-09-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-15 | 1987-03-17 | 1987-09-16 | $7700.00 | Window Closed / Lapsed |