GB2229269A - Surface moisture detection - Google Patents
Surface moisture detection Download PDFInfo
- Publication number
- GB2229269A GB2229269A GB9003148A GB9003148A GB2229269A GB 2229269 A GB2229269 A GB 2229269A GB 9003148 A GB9003148 A GB 9003148A GB 9003148 A GB9003148 A GB 9003148A GB 2229269 A GB2229269 A GB 2229269A
- Authority
- GB
- United Kingdom
- Prior art keywords
- moisture
- detecting
- radiation
- reflected
- surface moisture
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M3/00—Investigating fluid-tightness of structures
- G01M3/38—Investigating fluid-tightness of structures by using light
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N2021/1738—Optionally different kinds of measurements; Method being valid for different kinds of measurement
- G01N2021/1742—Optionally different kinds of measurements; Method being valid for different kinds of measurement either absorption or reflection
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N2021/8405—Application to two-phase or mixed materials, e.g. gas dissolved in liquids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/59—Transmissivity
- G01N21/5907—Densitometers
- G01N21/5911—Densitometers of the scanning type
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/06—Illumination; Optics
- G01N2201/069—Supply of sources
- G01N2201/0696—Pulsed
- G01N2201/0697—Pulsed lasers
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/08—Optical fibres; light guides
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
Surface moisture is detected by directing a beam of electromagnetic radiation (13) onto or through a surface (16), detecting radiation (10) reflected from or transmitted through the surface, and deriving from the detected radiation information concerning the surface moisture e.g. whether a surface is dry enough to paint or that a leak has occurred. A laser beam may be scanned over the surface and may travel down fibre optics. <IMAGE>
Description
Surface moisture detection
The present invention concerns the remote detection of surface moisture.
According to the present invention a method of detecting surface moisture comprises directing a localised beam of electromagnetic radiation onto a surface, detecting reflections from or transmissions through the surface, and noting changes in the reflected or transmitted radiation resulting from moisture on the surface.
The beam can be pulsed or continuous and a preferred form of beam is a continuous wave laser. The laser beam can be directed onto a fixed or constant position on the surface or alternatively the laser beam can scan over an area of the surface. The reflected or transmitted radiation can be detected and a signal obtained from the detected radiation and its characteristic displayed on an oscilloscope.
The invention can be performed in various ways and some specific embodiments with possible modifications will now be described by way of example with reference to the accompanying drawings in which:
Figure 1 is a diagrammatic view of one arrangement;
and
Figure 2 is a graph.
Referring to Figure 1, when a laser beam 10 from a laser 11 is directed onto a dry surface 12 a fraction of the incident light is reflected as at 13 and, if the reflectivity characteristics are stable, the fraction of the reflected power received by a remotely located detector 14 will be substantially constant. The detector 14 may provide an output signal in line 15. However, if moisture is present on the surface (as at 16) stability no longer exists due to such effects as motion of liquid molecules, surface tension and evaporation. These effects generate random changes in localised reflectivity coefficients. Consequently an incident laser beam exhibits corresponding random changes in reflected signals (see Figure 2) until the surface has completely dried out. The existence of changes in the reflected signal is therefore an indication that moisture is present on the surface.
In the above arrangement the laser beam 11 of electromagnetic radiation is directed onto a fixed or constant position on the surface 12. An alternative approach for detecting the presence of moisture over a large surface area is to employ a scanning laser. Under dry conditions this will generate a random scattered signal waveform characteristic on an oscilloscope detector screen. The present of any surface moisture will generate temporal instabilities in the characteristics. If the moisture is confined to a part of the surface being scanned then only the corresponding part of the characteristic will be affected, the remainder staying unchanged. In this way it is possible to rapidly monitor a surface for the presence of moisture.
It is anticipated that the method can be developed for the remote detection and location of leaks in, for example, vessels, conduits and flanges in addition to detecting spillage. Such remote detection and location can be useful for monitoring surfaces in plant for radioactive liquids. Additionally, the method can be useful for detecting the state of dryness of surfaces prior to painting or other operations, and the drying characteristics of surface preparations such as paint.
An alternative procedure for monitoring relatively large areas for moisture is to stop the laser beam by means, for example, of a computer-controlled orthogonal mirror arrangement. In this way a two-dimensional matrix type pattern of inspection locations can be produced, the laser image spot residing at each location for a fraction of a second. The distribution of moisture over the selected area can thus be quantified and displayed on a video display unit. Signals may be displayed above some selected threshold value to eliminate low level noise or spurious signals; or it is possible to confine displayed 'moisture' signals to levels above some selected minimum value.
In circumstances where optical line of sight conditions cannot be achieved or are inappropriate or the environment is hostile (thus precluding location of sensitive optical equipment close to the surface) optical signals can be delivered to and transmitted from the surface using fibre optics cables.
For fluid leak detection applications, involving insulated pipes or vessels, leaked fluid will eventually diffuse to the outer surface of the insulation. The highly unstable signals associated with moisture result from the vector summation at the detector of randomly varying scattered light signals. If too many signals are involved then averaging effects become dominant and the detector fluctuating signal output amplitude will decrease. Such a situation can exist with semi-porous surfaces such as mineral wool insulation and in order to compensate for this, small semi-permeable membranes can be located at the inspection points on the outer region of the insulation surface to limit penetration of light into the insulation and hence the number of scattered light signals at the detector. In this way signal to noise ratios can be significantly increased.Another way of increasing signal to noise ratios is to focus the incident laser beam. This will reduce the number of individual scattering events and also increase their scattered light intensity.
If light (incoherent or coherent) is directed onto a semitransparent substance with optical discontinuities arising, for example, from an open cellular structure or the fibres of mineral wool insulation, then significant scattering from the primary penetrating beam will result causing attenuation proportional to the depth of penetration.
This scattering and hence attenuation of a transmitted light beam will be reduced if the air spaces within the fibres or cells are filled with a transparent fluid such as water.
By directing a beam of light through a given thickness of the above material, a measure of its water content can thus be made by monitoring the amplitude of the transmitted signal. In this way the occurrence of any leaks in a pipe or vessel surrounded by this type of insulation can be detected and to some extent quantified the location of such a leak being deduced by comparing signals from different inspection sites.
Claims (7)
1. A method of detecting surface moisture comprising direction a localised beam of electromagnetic radiation onto a surface, detecting reflections from or transmissions through the surface, and noting changes in the reflected or transmitted radiation resulting from moisture on the surface.
A A method as claimed in Claim 1, in which the beam is pulsed.
3. A method as claimed in Claim 1, in which the beam is continuous.
4. A method as claimed in any preceding Claim, in which the beam is scanned over the surface.
5. A method as claimed in any preceding Claim, including detecting reflected or transmitted radiation, and obtaining from the detected radiation a signal indicative of characteristics of the detected radiation.
6. A method as claimed in any preceding Claim, in which the beam passes through a semi-permeable membrane before reaching the surface.
7. A method of detecting surface moisture substantially as hereinbefore described.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB898903556A GB8903556D0 (en) | 1989-02-16 | 1989-02-16 | Surface moisture detection |
Publications (3)
Publication Number | Publication Date |
---|---|
GB9003148D0 GB9003148D0 (en) | 1990-04-11 |
GB2229269A true GB2229269A (en) | 1990-09-19 |
GB2229269B GB2229269B (en) | 1993-04-21 |
Family
ID=10651809
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB898903556A Pending GB8903556D0 (en) | 1989-02-16 | 1989-02-16 | Surface moisture detection |
GB9003148A Expired - Fee Related GB2229269B (en) | 1989-02-16 | 1990-02-12 | Surface moisture detection |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB898903556A Pending GB8903556D0 (en) | 1989-02-16 | 1989-02-16 | Surface moisture detection |
Country Status (1)
Country | Link |
---|---|
GB (2) | GB8903556D0 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0568461A1 (en) * | 1992-04-29 | 1993-11-03 | MPB TECHNOLOGIES Inc. | Method and apparatus for non-contact, rapid and continuous moisture measurements |
EP0774395A2 (en) * | 1995-11-17 | 1997-05-21 | Ferrotron Elektronik GmbH | Method and device for detecting a lubricating film on rails |
WO2000079235A1 (en) * | 1999-06-23 | 2000-12-28 | Patrick Toomey | Water detection and source identification methods for structures using electromagnetic radiation spectroscopy |
GB2395784A (en) * | 1999-06-23 | 2004-06-02 | Patrick Toomey | Water and fungus detection methods for structures using electromagnetic radiation spectroscopy |
Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB371177A (en) * | 1931-05-07 | 1932-04-21 | B F Sturtevant Co | Improved method and means for controlling the vapour content or humidity of air and other gases |
GB1484613A (en) * | 1973-10-29 | 1977-09-01 | Karl G | Windscreen soiling sensor |
EP0005696A1 (en) * | 1977-03-19 | 1979-12-12 | Peter Dr.-Ing. Decker | Slippery road alarming device |
EP0009414A1 (en) * | 1978-09-25 | 1980-04-02 | Raymond James Noack | Apparatus and method for controlling windscreen wiper and windscreen washer apparatus of a vehicle |
GB2056059A (en) * | 1979-08-10 | 1981-03-11 | Bosch Gmbh Robert | A method of assessing the quality of a system comprising a wiper blade and the surface of a windscreen |
GB1596050A (en) * | 1978-05-30 | 1981-08-19 | Casswell P H | Vehicle window wiping arrangements |
GB2127540A (en) * | 1982-09-22 | 1984-04-11 | Unicell Ltd | Condensation prevention apparatus |
US4737629A (en) * | 1985-05-21 | 1988-04-12 | Nippondenso Co., Ltd. | Automatic windscreen defogger |
GB2208433A (en) * | 1987-07-31 | 1989-03-30 | Veglia Borletti Srl | Detecting water droplets on a vehicle window and controlling windscreen wiper in response thereto |
GB2208434A (en) * | 1987-07-31 | 1989-03-30 | Veglia Borletti Srl | Detecting water droplets on a vehicle window and controlling windscreen wiper in response thereto |
-
1989
- 1989-02-16 GB GB898903556A patent/GB8903556D0/en active Pending
-
1990
- 1990-02-12 GB GB9003148A patent/GB2229269B/en not_active Expired - Fee Related
Patent Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB371177A (en) * | 1931-05-07 | 1932-04-21 | B F Sturtevant Co | Improved method and means for controlling the vapour content or humidity of air and other gases |
GB1484613A (en) * | 1973-10-29 | 1977-09-01 | Karl G | Windscreen soiling sensor |
EP0005696A1 (en) * | 1977-03-19 | 1979-12-12 | Peter Dr.-Ing. Decker | Slippery road alarming device |
GB1596050A (en) * | 1978-05-30 | 1981-08-19 | Casswell P H | Vehicle window wiping arrangements |
EP0009414A1 (en) * | 1978-09-25 | 1980-04-02 | Raymond James Noack | Apparatus and method for controlling windscreen wiper and windscreen washer apparatus of a vehicle |
GB2056059A (en) * | 1979-08-10 | 1981-03-11 | Bosch Gmbh Robert | A method of assessing the quality of a system comprising a wiper blade and the surface of a windscreen |
GB2127540A (en) * | 1982-09-22 | 1984-04-11 | Unicell Ltd | Condensation prevention apparatus |
US4737629A (en) * | 1985-05-21 | 1988-04-12 | Nippondenso Co., Ltd. | Automatic windscreen defogger |
GB2208433A (en) * | 1987-07-31 | 1989-03-30 | Veglia Borletti Srl | Detecting water droplets on a vehicle window and controlling windscreen wiper in response thereto |
GB2208434A (en) * | 1987-07-31 | 1989-03-30 | Veglia Borletti Srl | Detecting water droplets on a vehicle window and controlling windscreen wiper in response thereto |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0568461A1 (en) * | 1992-04-29 | 1993-11-03 | MPB TECHNOLOGIES Inc. | Method and apparatus for non-contact, rapid and continuous moisture measurements |
EP0774395A2 (en) * | 1995-11-17 | 1997-05-21 | Ferrotron Elektronik GmbH | Method and device for detecting a lubricating film on rails |
EP0774395A3 (en) * | 1995-11-17 | 1998-08-05 | Ferrotron Elektronik GmbH | Method and device for detecting a lubricating film on rails |
WO2000079235A1 (en) * | 1999-06-23 | 2000-12-28 | Patrick Toomey | Water detection and source identification methods for structures using electromagnetic radiation spectroscopy |
GB2367616A (en) * | 1999-06-23 | 2002-04-10 | Patrick Toomey | Water detection and source identification methods for structures using electromagnetic radiation spectroscopy |
GB2395784A (en) * | 1999-06-23 | 2004-06-02 | Patrick Toomey | Water and fungus detection methods for structures using electromagnetic radiation spectroscopy |
GB2367616B (en) * | 1999-06-23 | 2004-06-16 | Patrick Toomey | Water detection and source identification methods for structures using electromagnetic radiation spectroscopy |
GB2395784B (en) * | 1999-06-23 | 2004-07-28 | Patrick Toomey | Water detection and source identification methods for structures using electromagnetic radiation spectroscopy |
Also Published As
Publication number | Publication date |
---|---|
GB2229269B (en) | 1993-04-21 |
GB8903556D0 (en) | 1989-04-05 |
GB9003148D0 (en) | 1990-04-11 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19990212 |