US5343045A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and device for measuring moisture content
Assignee: Ontario Hydro
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Filing: 1993-06-11
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Granted: 1994-08-30
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Expires: 2013-06-11
Abstract
Abstract A device for measuring the moisture content of an absorbent material, for example the paper insulation in an electrical transformer, uses a back scattered radiation technique to determine the absorption of light at specific wavelengths. A ratio of the back scattered radiation at different wavelengths can be compared against known values corresponding to a specific moisture content. An optical waveguide such as a bifurcated optical fibre is provided with a probe end optically coupled to a source end and a detection end, for transmitting light to the absorbent material and transmitting back scattered radiation to a detector.
Inventors
- 👤 Bal K. Gupta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 23:52
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/47; G01N21/4738
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
190 words
A device for measuring moisture content of an absorbent material, comprising an optical waveguide having a probe end optically coupled to source and detection ends, a source of electromagnetic radiation optically coupled to the source end of the optical waveguide, and means for measuring the flux of selected wavelengths optically coupled to the detection end of the optical waveguide, including a detector for measuring and means for displaying, recording or conveying a measurement of the flux of electromagnetic radiation emitted from the detection end of the waveguide at the selected wavelengths, wherein the means for measuring the flux comprises an optical chopper provided with a first optical filter for transmitting a first wavelength of electromagnetic radiation to the detector and a second optical filter for transmitting a second wavelength of electromagnetic radiation to the detector, the first wavelength being a wavelength at which absorption by water molecules is low and the second wavelength being a wavelength at which absorption by water molecules is high, the optical chopper including means for alternately interposing the first filter and the second filter between the detection end of the optical waveguide and the detector.
Claim 2
Independent Claim
190 words
A device for measuring moisture content of an absorbent material, comprising an optical waveguide having a probe end optically coupled to source and detection ends, a source of electromagnetic radiation optically coupled to the source end of the optical waveguide, and means for measuring the flux of selected wavelengths optically coupled to the detection end of the optical waveguide, including a detector for measuring and means for displaying, recording or conveying a measurement of the flux of electromagnetic radiation emitted from the detection end of the waveguide at the selected wavelengths, wherein the means for measuring the flux comprises an optical chopper provided with a first optical filter for transmitting a first wavelength of electromagnetic radiation to the detector and a second optical filter for transmitting a second wavelength of electromagnetic radiation to the detector, the first wavelength being a wavelength at which absorption by water molecules is low and the second wavelength being a wavelength at which absorption by water molecules is high, the optical chopper including means for alternately interposing the first filter and the second filter between the detection end of the optical waveguide and the detector.
Claim 3
Dependent Claim
15 words
The device claimed in claim 1 wherein the optical waveguide comprises a bifurcated optical fibre.
Claim 4
Dependent Claim
19 words
The device claimed in claim 1 wherein the probe end of the optical waveguide is provided with a spacer.
Claim 5
Dependent Claim
13 words
The device claimed in claim 1 wherein the detector comprises a photoconductive sensor.
Claim 6
Dependent Claim
28 words
The device claimed in claim 4 wherein the wavelength transmitted by the first filter is 1.81 μm and the wavelength transmitted by the second filter is 1.92 μm.
Claim 7
Dependent Claim
20 words
The device claimed in claim 1 further including a data acquisition computer for recording flux values measured by the detector.
Claim 8
Independent Claim
141 words
A method of measuring the moisture content of an absorbent material utilizing an optical waveguide having a probe end optically coupled to a source end and a detection end, comprising the steps of locating the probe end close to the material, transmitting electromagnetic radiation from the source end to the probe end and from the probe end to the detector end, employing an optical chopper and thereby, alternately detecting and measuring the flux values of two selected frequencies of electromagnetic radiation emitted from the detection end, the two selected frequencies of electromagnetic radiation corresponding to a first frequency which exhibits low absorption by water molecules and a second frequency which exhibits high absorption by water molecules and computing or calculating a ratio of the measured flux values and comparing the ratio to a pre-ascertained ratio corresponding to a known moisture content.
Claim 9
Independent Claim
141 words
A method of measuring the moisture content of an absorbent material utilizing an optical waveguide having a probe end optically coupled to a source end and a detection end, comprising the steps of locating the probe end close to the material, transmitting electromagnetic radiation from the source end to the probe end and from the probe end to the detector end, employing an optical chopper and thereby, alternately detecting and measuring the flux values of two selected frequencies of electromagnetic radiation emitted from the detection end, the two selected frequencies of electromagnetic radiation corresponding to a first frequency which exhibits low absorption by water molecules and a second frequency which exhibits high absorption by water molecules and computing or calculating a ratio of the measured flux values and comparing the ratio to a pre-ascertained ratio corresponding to a known moisture content.
Claim 10
Dependent Claim
15 words
The method claimed in claim 7 wherein the optical waveguide comprises a bifurcated optical fibre.
Claim 11
Dependent Claim
21 words
The method claimed in claim 7 wherein the probe end of the optical waveguide includes a spacer for contacting the material.
Claim 12
Dependent Claim
19 words
The method claimed in claim 7 wherein the selected wavelengths are in the infrared region of the electromagnetic spectrum.
Claim 13
Dependent Claim
16 words
The method claimed in claim 10 wherein the selected wavelengths are 1.81 μm and 1.92 μm.
Claim 14
Dependent Claim
20 words
The method claimed in claim 10 wherein the selected wavelengths are at or close to other absorption wavelengths of water.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-08-29 | 1998-02-28 | 1998-08-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-08-29 | 2002-02-28 | 2002-08-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-08-29 | 2006-02-28 | 2006-08-30 | $7700.00 | Window Closed / Lapsed |