WO1998035209A2 - Photodetector - Google Patents

Photodetector Download PDF

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Publication number
WO1998035209A2
WO1998035209A2 PCT/GB1998/000403 GB9800403W WO9835209A2 WO 1998035209 A2 WO1998035209 A2 WO 1998035209A2 GB 9800403 W GB9800403 W GB 9800403W WO 9835209 A2 WO9835209 A2 WO 9835209A2
Authority
WO
WIPO (PCT)
Prior art keywords
photodetector
chamber
photosensor
gas
baffle
Prior art date
Application number
PCT/GB1998/000403
Other languages
French (fr)
Other versions
WO1998035209A3 (en
Inventor
Malcolm Robert Snowball
Original Assignee
Water Recovery Plc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Water Recovery Plc filed Critical Water Recovery Plc
Priority to AU59995/98A priority Critical patent/AU5999598A/en
Publication of WO1998035209A2 publication Critical patent/WO1998035209A2/en
Publication of WO1998035209A3 publication Critical patent/WO1998035209A3/en

Links

Classifications

    • 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
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/15—Preventing contamination of the components of the optical system or obstruction of the light path
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/0252—Constructional arrangements for compensating for fluctuations caused by, e.g. temperature, or using cooling or temperature stabilization of parts of the device; Controlling the atmosphere inside a photometer; Purge systems, cleaning devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/0271—Housings; Attachments or accessories for photometers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/04—Optical or mechanical part supplementary adjustable parts
    • G01J1/0407—Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings
    • G01J1/0462—Slit arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/02—Constructional details
    • G01J5/05—Means for preventing contamination of the components of the optical system; Means for preventing obstruction of the radiation path
    • G01J5/051—Means for preventing contamination of the components of the optical system; Means for preventing obstruction of the radiation path using a gas purge
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/02—Constructional details
    • G01J5/08—Optical arrangements
    • G01J5/0856—Slit arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J2001/0276—Protection
    • G01J2001/028—Protection against liquid

Definitions

  • This invention relates to a photodetector, and more particularly to a photodetector for detecting photo intensity through a liquid.
  • UV light has germicidal properties which can be used to sterilise water. This effect occurs at a wavelength of 245-265nM, and thus it is important to ensure that the UV light is working and that it is working at the right wavelength, otherwise foreign matter in the water may pass through the sterilise untreated.
  • WO95/09814 discloses a photodetector for detecting the
  • the photodetector comprises a photosensor which is separated from the water by a window that is coated in PTFE.
  • the purpose of the PTFE is to ensure that slime and other matter does not build up on the window and attenuate the light entering the photodiode.
  • the PTFE coating only has a limited ability to keep the window clean, and is not effective at keeping the window clean when the liquid contains solid sewage in suspension.
  • a photodetector comprising a body which defines a chamber that is open at one end, a photosensor mounted to the body and arranged to sense light entering the chamber through its open end, a layer of gas being disposed in the chamber between the photosensor and the open end of the chamber .
  • the layer of gas will form a barrier between the photosensor and any liquid.
  • Preferably means are provided for supplying a continuous flow of gas to the chamber, so that any gas which becomes displaced will be replenished.
  • the photosensor in preferably directed along a path which extends centrally through the open end of the chamber. Any bubbling which does occur will occur around the edges of the chamber and will thus not affect the photosensor.
  • a baffle is disposed between the chamber and the photosensor, the photosensor being directed through a passageway in the baffle.
  • the baffle acts as a shield to prevent splashes of liquid from reaching the photosensor.
  • the means for supplying gas is connected to a point between the baffle and the photosensor, so that gas flows along said passageway through the baffle, and thereby creates a draft which prevents splashes of liquid from travelling along the passageway in the opposite direction.
  • the gas comprises air.
  • the gas is supplied by a pump, a fan, a compressor or a cylinder of gas.
  • the photosensor comprises a photodetector device which is separated from the chamber by a window.
  • the photosensor comprises an iris which is adjustable to vary the amount of light incident on the photodetector device.
  • the iris comprises an aperture and adjustment means which is displaceable into or out of the aperture in order to vary its cross-sectional area.
  • the adjustment member comprises a screw.
  • a liquid treatment apparatus comprising a treatment chamber and a photodetector as hereinbefore described mounted to a wall of the treatment chamber .
  • the photodetector is mounted such that the open mouth of its chamber is directed downwardly, thereby trapping the gas inside the photodetector chamber.
  • An embodiment of this invention will now be described by way of an example only, and with reference to the accompanying drawing, the single Figure of which is a sectional view of a photodetector mounted to a liquid treatment apparatus. Referring to the drawing, there is shown a photodetector 10 mounted to a wall 11 of an elongate treatment duct of a liquid sterilisation apparatus 12. The apparatus comprises a pair of elongate ultra-violet lamps 13 , which extend axially along the treatment duct.
  • the photodetector 10 comprises a head portion 14 and a body 15.
  • the head 14 comprises an externally screw-threaded neck which houses a vacuum photo-diode, (not shown) and which is engaged with the upper end of an internally screw-threaded tube 16 on the body 15.
  • the lower end of the tube 16 is attached to the upper wall of a chamber 17.
  • the chamber 17 comprises a tubular side wall, which extends partially through an opening in the wall 11 of the liquid treatment duct.
  • the lower end of the side wall of the chamber 17 is welded to the wall 11 around the opening therein, in order to provided a good seal.
  • the chamber 17 is divided into upper and lower portions 17a, 17b by a plate 18, which is mounted normal to the axis of the neck of the photodetector head 14.
  • the chamber 17 is open at its lower end to the liquid in the treatment duct.
  • An aperture 19 is formed in the plate in line with the axis of the neck of the photodetector, and in line with an aperture 20 in the upper wall of the chamber 17.
  • the tube 16 of the photodetector is closed at its lower end by a quartz glass window 21.
  • a screw 23 extends through the wall of the tube 16 and radially projects into the centre of the iris 22.
  • the upper part 17a of the photodetector chamber 17 is connected to an air supply by a tube 24 which extends through its side wall.
  • the liquid treatment apparatus is mounted such that the open bottom of the photodetector chamber 17 faces downwardly, as shown in the drawing. Air is pumped or fed into the upper part 17a of the photodetector chamber 17. The air flows downwardly through the aperture 19 in the plate 18 and displaces any fluid in the lower part 17b of the chamber 17. Once the chamber 17 has filled with air, excess air bubbles out of the bottom of the chamber 17 and is carried away with the flow of liquid in the duct.
  • the vacuum photodiode inside the detector head 14 senses the intensity of the UV light emitted from the lamps 13.
  • the quartz glass window which separates the detector head 14 from the liquid does not come into contact with the liquid owing to the air pocket which is created inside the chamber. Some air may be swept away with the flow of liquid through the duct, but this is continuously replenished by the air emerging from the tube 24.
  • the apertured plate 18 acts as a baffle and prevents splashes of liquid from reaching the quartz glass window 21.
  • the aperture 19 in the plate 18 allows light to pass from the duct to the photodiode, however liquid is prevented from entering the upper part 17a of the chamber by the velocity of the air that is flowing through the aperture 19.
  • the continuous airflow also helps to prevent the build up of moisture inside the chamber 17.
  • the air may also be heated in order to prevent condensation on the quartz glass window 21.
  • the amount of light that is incident on the photodetector can be varied by turning the screw 23, so as to vary the cross-sectional area of the aperture in the iris 22.

Abstract

A photodetector for detecting photo intensity through a liquid comprises a body (15), which defines a chamber (17) that is open at one end, a photosensor (14) mounted to the body and arranged to sense light entering the chamber (17) through its open end, a layer of air being disposed in the chamber between the photosensor and the open end of the chamber. The layer of air forms a barrier between the photosensor (14) and the liquid and thus slime and other matter is unable to build up in front of the photosensor.

Description

Photodβtector
This invention relates to a photodetector, and more particularly to a photodetector for detecting photo intensity through a liquid.
It is well known that high intensity UV light has germicidal properties which can be used to sterilise water. This effect occurs at a wavelength of 245-265nM, and thus it is important to ensure that the UV light is working and that it is working at the right wavelength, otherwise foreign matter in the water may pass through the sterilise untreated. WO95/09814 discloses a photodetector for detecting the
UV photo intensity inside the treatment chamber of a water treatment apparatus. The photodetector comprises a photosensor which is separated from the water by a window that is coated in PTFE. The purpose of the PTFE is to ensure that slime and other matter does not build up on the window and attenuate the light entering the photodiode.
We have found that the PTFE coating only has a limited ability to keep the window clean, and is not effective at keeping the window clean when the liquid contains solid sewage in suspension.
We have now devised a photodetector which alleviates the above-mentioned problems.
In accordance with this invention as seen from a first aspect, there is provided a photodetector comprising a body which defines a chamber that is open at one end, a photosensor mounted to the body and arranged to sense light entering the chamber through its open end, a layer of gas being disposed in the chamber between the photosensor and the open end of the chamber . In use, the layer of gas will form a barrier between the photosensor and any liquid. Thus, slime and other matter is unable to build up in front of the photosensor.
Preferably means are provided for supplying a continuous flow of gas to the chamber, so that any gas which becomes displaced will be replenished.
In order to prevent the gas from bubbling in front of the field of view of the photosensor, the photosensor in preferably directed along a path which extends centrally through the open end of the chamber. Any bubbling which does occur will occur around the edges of the chamber and will thus not affect the photosensor.
Preferably a baffle is disposed between the chamber and the photosensor, the photosensor being directed through a passageway in the baffle. The baffle acts as a shield to prevent splashes of liquid from reaching the photosensor. Preferably the means for supplying gas is connected to a point between the baffle and the photosensor, so that gas flows along said passageway through the baffle, and thereby creates a draft which prevents splashes of liquid from travelling along the passageway in the opposite direction. Preferably the gas comprises air. Preferably the gas is supplied by a pump, a fan, a compressor or a cylinder of gas.
Preferably the photosensor comprises a photodetector device which is separated from the chamber by a window. Preferably the photosensor comprises an iris which is adjustable to vary the amount of light incident on the photodetector device.
Preferably the iris comprises an aperture and adjustment means which is displaceable into or out of the aperture in order to vary its cross-sectional area.
Preferably the adjustment member comprises a screw.
Also in accordance with this invention as seen from a second aspect, there is provided a liquid treatment apparatus comprising a treatment chamber and a photodetector as hereinbefore described mounted to a wall of the treatment chamber .
Preferably the photodetector is mounted such that the open mouth of its chamber is directed downwardly, thereby trapping the gas inside the photodetector chamber. An embodiment of this invention will now be described by way of an example only, and with reference to the accompanying drawing, the single Figure of which is a sectional view of a photodetector mounted to a liquid treatment apparatus. Referring to the drawing, there is shown a photodetector 10 mounted to a wall 11 of an elongate treatment duct of a liquid sterilisation apparatus 12. The apparatus comprises a pair of elongate ultra-violet lamps 13 , which extend axially along the treatment duct.
The photodetector 10 comprises a head portion 14 and a body 15. The head 14 comprises an externally screw-threaded neck which houses a vacuum photo-diode, (not shown) and which is engaged with the upper end of an internally screw-threaded tube 16 on the body 15. The lower end of the tube 16 is attached to the upper wall of a chamber 17.
The chamber 17 comprises a tubular side wall, which extends partially through an opening in the wall 11 of the liquid treatment duct. The lower end of the side wall of the chamber 17 is welded to the wall 11 around the opening therein, in order to provided a good seal.
The chamber 17 is divided into upper and lower portions 17a, 17b by a plate 18, which is mounted normal to the axis of the neck of the photodetector head 14. The chamber 17 is open at its lower end to the liquid in the treatment duct.
An aperture 19 is formed in the plate in line with the axis of the neck of the photodetector, and in line with an aperture 20 in the upper wall of the chamber 17. The tube 16 of the photodetector is closed at its lower end by a quartz glass window 21.
An iris 22, which comprises an annular ring, is mounted in the tube 16 normal to the axis thereof. A screw 23 extends through the wall of the tube 16 and radially projects into the centre of the iris 22. The upper part 17a of the photodetector chamber 17 is connected to an air supply by a tube 24 which extends through its side wall.
In use, the liquid treatment apparatus is mounted such that the open bottom of the photodetector chamber 17 faces downwardly, as shown in the drawing. Air is pumped or fed into the upper part 17a of the photodetector chamber 17. The air flows downwardly through the aperture 19 in the plate 18 and displaces any fluid in the lower part 17b of the chamber 17. Once the chamber 17 has filled with air, excess air bubbles out of the bottom of the chamber 17 and is carried away with the flow of liquid in the duct.
The vacuum photodiode inside the detector head 14 senses the intensity of the UV light emitted from the lamps 13. The quartz glass window which separates the detector head 14 from the liquid does not come into contact with the liquid owing to the air pocket which is created inside the chamber. Some air may be swept away with the flow of liquid through the duct, but this is continuously replenished by the air emerging from the tube 24.
The apertured plate 18 acts as a baffle and prevents splashes of liquid from reaching the quartz glass window 21. The aperture 19 in the plate 18 allows light to pass from the duct to the photodiode, however liquid is prevented from entering the upper part 17a of the chamber by the velocity of the air that is flowing through the aperture 19.
The continuous airflow also helps to prevent the build up of moisture inside the chamber 17. The air may also be heated in order to prevent condensation on the quartz glass window 21.
The amount of light that is incident on the photodetector can be varied by turning the screw 23, so as to vary the cross-sectional area of the aperture in the iris 22.

Claims

Claims
1) A photodetector comprising a body which defines a chamber that is open at one end, a photosensor mounted to the body and arranged to sense light entering the chamber through its open end, a layer of gas being disposed in the chamber between the photosensor and the open end of the chamber.
2) A photodetector as claimed in claim 1, in which the photosensor is preferably directed along a path which extends centrally through the open end of the chamber.
3) A photodetector as claimed in claims 1 or 2 , in which a baffle is disposed between the chamber and the photosensor, the photosensor being directed through a passageway in the baffle.
4) A photodetector as claimed in any preceding claim, comprising means for supplying a continuous flow of gas to the chamber .
5) A photodetector as claimed in claim 4 as appended to claim 3 , in which the means for supplying gas is connected to a point between the baffle and the photosensor.
6) A photodetector as claimed in claims 4 or 5 , in which the gas comprises air.
7) A photodetector as claimed in any of claims 4 to 6 , in which the gas is supplied by a pump.
8) A photodetector as claimed in any of claims 4 to 6 , in which the gas is supplied by a fan.
9) A photodetector as claimed in any of claims 4 to 6 , in which the gas is supplied by a compressor.
10) A photodetector as claimed in any of claims 4 to 6, in which the gas is supplied by a cylinder of gas. 11) A photodetector as claimed in any preceding claim, in which the photosensor comprises a photodetector device which is separated from the chamber by a window.
12) A photodetector as claimed in any preceding claim, in which the photosensor comprises an iris which is adjustable to vary the amount of light incident on the photodetector device.
13) A photodetector as claimed in claim 12, in which the iris comprises an aperture and adjustment means which is displaceable into or out of the aperture in order to vary its cross-sectional area.
14) A photodetector as claimed in claim 13, in which the adjustment member comprises a screw.
15) A liquid treatment apparatus comprising a treatment chamber and a photodetector as claimed in any preceding claim, mounted to a wall of the treatment chamber.
16) A liquid treatment apparatus as claimed in claim 15, in which the photodetector is mounted such that the open mouth of its chamber is directed downwardly.
PCT/GB1998/000403 1997-02-08 1998-02-09 Photodetector WO1998035209A2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU59995/98A AU5999598A (en) 1997-02-08 1998-02-09 Photodetector

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9702599.3A GB9702599D0 (en) 1997-02-08 1997-02-08 Photodetector
GB9702599.3 1997-02-08

Publications (2)

Publication Number Publication Date
WO1998035209A2 true WO1998035209A2 (en) 1998-08-13
WO1998035209A3 WO1998035209A3 (en) 1998-09-17

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1998/000403 WO1998035209A2 (en) 1997-02-08 1998-02-09 Photodetector

Country Status (3)

Country Link
AU (1) AU5999598A (en)
GB (1) GB9702599D0 (en)
WO (1) WO1998035209A2 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105352592A (en) * 2015-08-07 2016-02-24 佛山市美的清湖净水设备有限公司 Ultraviolet intensity detects frock and ultraviolet lamp fixing device who is applicable to it
CN105698926A (en) * 2014-11-25 2016-06-22 贺利氏特种光源美国有限责任公司 Tunable photo-detector device
WO2019199578A1 (en) * 2018-04-12 2019-10-17 Frost Control Systems, Inc. Measurement system

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3827752A1 (en) * 1988-08-16 1990-02-22 Harald Dipl Ing Gosebruch Method and apparatus for detecting the surface of grinding wheels
EP0456202A2 (en) * 1990-05-11 1991-11-13 Applied Materials, Inc. Particle monitor system and method
US5493124A (en) * 1994-04-28 1996-02-20 Infilco Degremont, Inc. Apparatus for measuring radiation transmittance of a process fluid

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3827752A1 (en) * 1988-08-16 1990-02-22 Harald Dipl Ing Gosebruch Method and apparatus for detecting the surface of grinding wheels
EP0456202A2 (en) * 1990-05-11 1991-11-13 Applied Materials, Inc. Particle monitor system and method
US5493124A (en) * 1994-04-28 1996-02-20 Infilco Degremont, Inc. Apparatus for measuring radiation transmittance of a process fluid

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105698926A (en) * 2014-11-25 2016-06-22 贺利氏特种光源美国有限责任公司 Tunable photo-detector device
EP3029437A3 (en) * 2014-11-25 2016-09-21 Heraeus Noblelight America LLC Tunable photo-detector device
US9989410B2 (en) 2014-11-25 2018-06-05 Heraeus Noblelight America Llc Tunable photo-detector device
CN105352592A (en) * 2015-08-07 2016-02-24 佛山市美的清湖净水设备有限公司 Ultraviolet intensity detects frock and ultraviolet lamp fixing device who is applicable to it
WO2019199578A1 (en) * 2018-04-12 2019-10-17 Frost Control Systems, Inc. Measurement system

Also Published As

Publication number Publication date
WO1998035209A3 (en) 1998-09-17
GB9702599D0 (en) 1997-03-26
AU5999598A (en) 1998-08-26

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