US4793181A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Constant temperature sorption hygrometer
Assignee: GULATI JACK D
•
Filing: 1987-06-02
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Granted: 1988-12-27
•
Expires: 2007-06-02
Abstract
Abstract A constant temperature sorption hygrometer comprising a differential pair of substrate-supported heated metal film sensing elements, one coated with a hygroscopic layer of microporous aluminum oxide and the other coated with a non-hygroscopic protective coating or uncoated, both operated by feedback controlled constant temperature bridge circuits; together with alternate forms of hygrometer transducer apparatus employing differential sorption detection of water vapor.
Inventors
- 👤 Robert S. Djorup
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:41
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/12; G01N27/121
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
99 words
Hygrometer comprising: a pair of temperature coefficient resistive sensing elements, one of the elements including a hygroscopic material and the other element being substantially non-hygroscopic; a transducer Wheatstone bridge including the pair of sensing elements as two of the transducer bridge arms; a heating Wheatstone bridge including the transducer bridge as one arm of the heating bridge; a feedback controlled electrical circuit adapted to maintain the resistance of the transducer bridge constant; and circuitry adapted to measure the transducer bridge imbalance, the imbalance being relate to the amount of water adsorbed by the sensing element including the hygroscopic material.
Claim 2
Dependent Claim
99 words
Hygrometer comprising: a pair of temperature coefficient resistive sensing elements, one of the elements including a hygroscopic material and the other element being substantially non-hygroscopic; a transducer Wheatstone bridge including the pair of sensing elements as two of the transducer bridge arms; a heating Wheatstone bridge including the transducer bridge as one arm of the heating bridge; a feedback controlled electrical circuit adapted to maintain the resistance of the transducer bridge constant; and circuitry adapted to measure the transducer bridge imbalance, the imbalance being relate to the amount of water adsorbed by the sensing element including the hygroscopic material.
Claim 3
Dependent Claim
12 words
The hygrometer of claim 1 wherein the hygroscopic material is aluminum oxide.
Claim 4
Dependent Claim
13 words
The hygrometer of claim 1 wherein the hygroscopic material is a hygroscopic polymer.
Claim 5
Dependent Claim
13 words
The hygrometer of claim 1 wherein the hygroscopic material is a hygroscopic copolymer.
Claim 6
Dependent Claim
13 words
The hygrometer of claim 1 wherein the hygroscopic material is hydroxyl ethyl cellulose.
Claim 7
Dependent Claim
13 words
The hygrometer of claim 1 wherein the hygroscopic material is carboxyl methyl cellulose.
Claim 8
Dependent Claim
13 words
The hygrometer of claim 1 wherein the hygroscopic material is a cellulose ester.
Claim 9
Dependent Claim
12 words
The hygrometer of claim 1 wherein the hygroscopic material is vinylene carbonate.
Claim 10
Dependent Claim
12 words
The hygrometer of claim 1 wherein the hygroscopic material is vinyl acetate.
Claim 11
Dependent Claim
12 words
The hygrometer of claim 1 wherein tee hygroscopic material is beryllium oxide.
Claim 12
Dependent Claim
13 words
The hygrometer of claim 1 wherein the hygroscopic material is a metal oxide.
Claim 13
Dependent Claim
11 words
The hygrometer of claim 11 wherein the metal oxide includes silicon.
Claim 14
Dependent Claim
11 words
The hygrometer of claim 11 wherein the metal oxide includes nickel.
Claim 15
Dependent Claim
19 words
The hygrometer of claim 1 wherein the sensing elements include a cylindrical refractory substrate coated with a conductive material.
Claim 16
Dependent Claim
11 words
The hygrometer of claim 14 wherein the conductive material is platinum.
Claim 17
Dependent Claim
21 words
The hygrometer of claim 14 wherein the hydroscopic material of one of the elements forms a coating over the conductive material.
Claim 18
Dependent Claim
12 words
The hygrometer of claim 16 wherein the hygroscopic coating is aluminum oxide.
Claim 19
Dependent Claim
11 words
The hygrometer of claim 14 wherein the substrate is aluminum oxide.
Claim 20
Dependent Claim
16 words
The hygrometer of claim 1 wherein the pair elements are both mounted on a single substrate.
Claim 21
Dependent Claim
11 words
The hygrometer of claim 19 wherein the substrate is substantially flat.
Claim 22
Dependent Claim
34 words
The hygrometer of claim 1 wherein the circuit adapted to measure the transducer bridge imbalance includes an amplifier connected between the two resistive sensing elements and between two other resistors of the transducer bridge.
Claim 23
Dependent Claim
15 words
The hygrometer of claim 1 wherein the feedback controlled electrical circuit includes a differential amplifier.
References Cited (Backward Citations)
US1855774A
Cited
US2237006A
Cited
US2707880A
Cited
US3075385A
Cited
US3164004A
Cited
US3253219A
Cited
US3350941A
Cited
US3523244A
Cited
US3582728A
Cited
US3802268A
Cited
US4164868A
Cited
US4143177A
Cited
US4419888A
Cited
US4379406A
Cited
US4562725A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-12-27 | 1992-06-27 | 1992-12-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-12-27 | 1996-06-27 | 1996-12-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-12-27 | 2000-06-27 | 2000-12-27 | $7700.00 | Window Closed / Lapsed |