Abstract:
An optical radiation sensor device for detecting radiation in a radiation field having a thickness. A preferred embodiment of the device includes a radiation source and a radiation sensor element positioned to receive radiation from the radiation source. A motor (or other motive means) is provided to alter the thickness of the radiation field from a first thickness to a second thickness. The sensor element is capable of detecting and responding to incident radiation from radiation source at the first thickness and at the second thickness. The optical radiation sensor device allows for determination of radiation (preferably ultraviolet radiation) transmittance of a fluid of interest.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    The present application claims the benefit under 35 U.S.C. §119(e) of provisional patent application Ser. No. 60/211,971, filed Jun. 16, 2000, the contents of which are hereby incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    In one of its aspects, the present invention relates to an optical radiation sensor system. In another of its aspects, the present invention relates to a method for measuring radiation transmittance of a fluid.  
           [0004]    2. Description of the Prior Art  
           [0005]    Optical radiation sensors are known and find widespread use in a number of applications. One of the principal applications of optical radiation sensors is in the field of ultraviolet radiation fluid disinfection systems.  
           [0006]    It is known that the irradiation of water with ultraviolet light will disinfect the water by inactivation of microorganisms in the water, provided the irradiance and exposure duration are above a minimum “dose” level (often measured in units of milliWatt seconds per square centimeter or mW·s/cm 2 ). Ultraviolet water disinfection units such as those commercially available from Trojan Technologies Inc. under the tradenames Trojan UVMax™, Trojan UVSwift™ and Trojan UVLogic™, employ this principle to disinfect water for human consumption. Generally, water to be disinfected passes through a pressurized stainless steel cylinder which is flooded with ultraviolet radiation. Large scale municipal waste water treatment equipment such as that commercially available from Trojan Technologies Inc. under the tradenames UV3000 and UV4000, employ the same principal to disinfect waste water. Generally, the practical applications of these treatment systems relates to submersion of a treatment module or system in an open channel wherein the wastewater is exposed to radiation as it flows past the lamps. For further discussion of fluid disinfection systems employing ultraviolet radiation, see any one of the following:  
           [0007]    U.S. Pat. No. 4,482,809,  
           [0008]    U.S. Pat. No. 4,872,980,  
           [0009]    U.S. Pat. No. 5,006,244,  
           [0010]    U.S. Pat. No. 5,418,370,  
           [0011]    U.S. Pat. No. 5,539,210, and  
           [0012]    U.S. Pat. No. Re36,896.  
           [0013]    In many applications, it is desirable to monitor the level of ultraviolet radiation present within the water (or other fluid) under treatment or other investigation. In this way, it is possible to assess, on a continuous or semi-continuous basis, the level of ultraviolet radiation, and thus the overall effectiveness and efficiency of the disinfection process.  
           [0014]    It is known in the art to monitor the ultraviolet radiation level by deploying one or more passive sensor devices near the operating lamps in specific locations and orientations which are remote from the operating lamps. These passive sensor devices may be photodiodes, photoresistors or other devices that respond to the impingent of the particular radiation wavelength or range of radiation wavelengths of interest by producing a repeatable signal level (e.g., in volts or amperes) on output leads.  
           [0015]    In most commercial ultraviolet water disinfection systems, the single largest operating cost relates to the cost of electricity to power the ultraviolet radiation lamps. In a case where the transmittance of the fluid varies from time to time, it would be very desirable to have a convenient means by which fluid transmittance could be measured for the fluid being treated by the system (or the fluid being otherwise investigated) at a given time. If it is found that fluid transmittance is relatively high, it might be possible to reduce power consumption in the lamps by reducing the output thereof. In this way, the significant savings in power costs would be possible.  
           [0016]    The measurement of fluid transmittance is desirable since measurement of intensity alone is not sufficient to characterize the entire radiation field—i.e., it is not possible to separate the linear effects of lamp aging and fouling from exponential effects of transmittance. Further, dose delivery is a function of the entire radiation field, since not all fluid takes the same path.  
           [0017]    The prior art has endeavoured to develop reliable radiation (particularly UV) transmittance measuring devices.  
           [0018]    For example, it is known to use a single measurement approach. Unfortunately, the single measurement distance requires re-calibration with fluid of known transmittance to account for fouling.  
           [0019]    It is also known to use a two-sensor system in which a first sensor is disposed in air and a second sensor is disposed in water. The problem with this approach is that it results in different fouling of each sensor with resulting errors.  
           [0020]    Further, some systems require obtaining a sample from a channel of flowing fluid and thereafter measuring the radiation transmittance of the sample. Unfortunately, this approach necessitates the use of additional fluid handling measures which can lead to non-representative samples.  
           [0021]    Thus, despite the advances made in the art, there exists a need for an improved device which can measure radiation transmittance of a fluid. Ideally, the device would have one or more of the following characteristics: it would be of simple construction, it would be submersible, it would require only a single sensor and it could be implemented to measure UV transmittance of a fluid in an on-line or random measurement manner.  
         SUMMARY OF THE INVENTION  
         [0022]    It is an object of the present invention to provide a novel optical sensor device which obviates or mitigates at least one of the above-mentioned disadvantages of the prior art.  
           [0023]    It is another object of the present invention to provide a novel radiation source module which obviates or mitigates at least one of the above-mentioned disadvantages of the prior art.  
           [0024]    It is another object of the present invention to provide a novel process for measuring the transmittance of a fluid in a radiation field.  
           [0025]    Accordingly, in one of its aspects, the present invention provides an optical radiation sensor device for detecting radiation in a radiation field having a thickness, the device comprising:  
           [0026]    a radiation source;  
           [0027]    a radiation sensor element positioned to receive radiation from the radiation source; and  
           [0028]    motive means to alter the thickness of the radiation field from a first thickness to a second thickness;  
           [0029]    the sensor element capable of detecting and responding to incident radiation from radiation source at the first thickness and at the second thickness.  
           [0030]    In another of its aspects, the present invention provides a process for measuring transmittance of a fluid in a radiation field, the process comprising the steps of:  
           [0031]    (i) positioning a radiation source and a radiation sensor element in a spaced relationship to define a first thickness of fluid in the radiation field;  
           [0032]    (ii) detecting a first radiation intensity corresponding to radiation received by the sensor element at the first thickness;  
           [0033]    (iii) altering the first thickness to define a second thickness;  
           [0034]    (iv) detecting a second radiation intensity corresponding to radiation received by the sensor element at the second thickness; and  
           [0035]    (v) calculating radiation transmittance of the fluid in the radiation field from the first radiation intensity and the second radiation intensity.  
           [0036]    In another of its aspects, the present invention provides an optical radiation sensor device for detecting radiation in a radiation field generated in a fluid of interest, the device comprising:  
           [0037]    a radiation source submersible in the fluid of interest;  
           [0038]    a submersible first radiation sensor element positioned in the fluid of interest at a first distance from the radiation source; and  
           [0039]    a submersible second radiation sensor element positioned in the fluid of interest at a second distance from the radiation source;  
           [0040]    wherein: (i) the first distance is different from the second distance, (ii) the first radiation sensor element is capable of detecting and responding to incident radiation from radiation source at the first distance, and (iii) the second radiation sensor element is capable of detecting and responding to incident radiation from radiation source at the second distance.  
           [0041]    Thus, the present inventors have discovered a novel optical sensor device which, in a preferred embodiment is simplified in construction in that it only requires a single lamp and single sensor element. The sensor element and radiation source (preferably an ultraviolet radiation lamp) are arranged to create a fluid layer therebetween. By altering the thickness of the fluid layer, it is possible to take multiple (i.e., two or more) radiation intensity readings at multiple, known fluid layer thicknesses. Once these are achieved, using conventional calculations, it is possible to readily calculate the radiation transmittance of the fluid. A process for measuring transmittance of a fluid is also described for implementation of the present optical radiation sensor device. Other advantages will become apparent to those of skill in the art. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0042]    Embodiments of the present invention will be described with reference to the accompanying drawings, wherein like numerals designate like elements, and in which:  
         [0043]    [0043]FIG. 1 illustrates a side elevation view of an embodiment of the present optical radiation sensor device;  
         [0044]    [0044]FIG. 2 illustrates a cross-sectional view of the device illustrated in FIG. 1;  
         [0045]    [0045]FIG. 3 illustrates an alternate embodiment of the optical radiation sensor device illustrated in FIG. 2;  
         [0046]    [0046]FIG. 4 illustrates a further alternate embodiment to the optical radiation sensor device illustrated in FIG. 2;  
         [0047]    [0047]FIG. 5 illustrates a cross-sectional view of an alternate embodiment of the present optical radiation sensor device;  
         [0048]    [0048]FIG. 6 illustrates yet a further alternate embodiment of the optical radiation sensor device illustrated in FIG. 2; and  
         [0049]    [0049]FIG. 7 illustrates yet a further alternate embodiment of the optical radiation sensor device illustrated in FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0050]    With reference to FIGS. 1 and 2, there is illustrated an optical radiation sensor device  100 . Sensor device  100  comprises a fluid tight housing  105  which comprises a sensor housing  110  and a radiation source housing  115 .  
         [0051]    Sensor housing  110  has attached to a terminal portion thereof a boot  120 . Boot  120  can be made of any suitable flexible material which is fluid tight and can withstand the rigours of the radiation environment in which it is used. For example, boot  120  may be constructed of Neoprene™, Viton™ and the like. Boot  120  may be sealably attached to the terminal end of sensor housing  110  in any conventional manner (not shown). Disposed at the distal end of boot  120  is a radiation transparent window  125 .  
         [0052]    Disposed within sensor housing  110  is a motor  130 . Also disposed within sensor housing  110  is a slidable first disk  135  which is connected to a pair of rods  140 , 145 . Rods  140 , 145  are, in turn, connected a second disk  150  having disposed therein radiation transparent window  125 . Disposed between rods  140 , 145  is an optical sensor  155  which contains a photodiode (not shown) or other radiation sensor material. The sensor itself may be chosen from conventional sensors. For example, a suitable sensor is commercially available from IFW (Germany).  
         [0053]    As illustrated, a screw rod  160  interconnects motor  130  and first disk  135 .  
         [0054]    Disposed within radiation source housing  115  is a ballast  165  conventionally used to control a radiation source such as an ultraviolet lamp.  
         [0055]    A connection block  170  is connected to the distal end of radiation source housing  115  in a fluid tight manner.  
         [0056]    A radiation source  175  emanates from and is in a fluid tight engagement with connection block  170 . Radiation source  175  is conventional. Preferably, radiation source  175  is an ultraviolet radiation lamp, more preferably such a lamp encased in a radiation transparent protective sleeve (e.g., a sleeve made of quartz).  
         [0057]    As will be apparent and appreciated by those of skill in the art, it is conventional to have a electrical leads emanating from motor  130 , optical sensor  155  and ballast  165  through sensor housing  110  and radiation source housing  115 , respectively, and then through a fluid tight conduit  180 . For clarity and understanding the illustrated embodiment, the electrical leads have not been shown. Thus, those of skill in the art will recognize that illustrated optical radiation sensor device  100  is designed to be entirely submersible in the fluid of interest.  
         [0058]    As will be apparent, fluid passing through optical sensor device  100  will, at least in part, pass through a gap A created between second disk  150  and radiation source  175 . In other places in the specification, this gap is referred to as a fluid layer, particularly a fluid layer having a specific thickness.  
         [0059]    The fluid layer thickness between disk  150  and radiation source  175  may be altered in the following manner. Motor  130  is actuated thereby actuating screw rod  160  which will serve to retract first disk  135  and rods  140 , 145  into sensor housing  110 . This has the effect of increasing the thickness of gap A between second disk  150  and radiation source  175  or, in other words, increasing the thickness of the fluid layer.  
         [0060]    Through the use of conventional stepper motors, position sensors, mechanical constraints (e.g., fixture travel means such as a solenoid, a cam, a crank shaft, physical stops and other relatively simple mechanical constructions) or the like, it is possible to take measurements of the radiation intensity detected by sensor  155  at various, known values for gap A. Once various intensities at various gaps are known, the radiation transmittance of fluid passing through optical radiation sensor device  100  may be readily determined as will be explained hereinbelow.  
         [0061]    As will be appreciated by those with skill in the art, in the embodiment illustrated in FIGS. 1 and 2, sensor  155  and radiation source  175  are stationary. Specifically, the fluid layer thickness is altered by movement of second disk  150  with respect to radiation source  175 .  
         [0062]    [0062]FIGS. 3 and 4 illustrate alternate embodiments for varying the thickness of the fluid layer. In FIGS.  1 - 4 , like reference numerals designate like elements. In FIG. 3, the reference numerals for elements which have been moved and/or modified from FIG. 1 carry the suffix “a”. Similarly, in FIG. 4, the reference numerals for elements which have been moved and/or modified from FIG. 1 carry the suffix “b”.  
         [0063]    With reference to FIG. 3, it will be seen that the distal end of sensor housing  110  has been modified to include a body  185  within which sensor  155   a  is movable. Movement of sensor  155   a  may be accomplished by placing a motor  130   a  which is interconnected to sensor  155   a  via a screw rod  160   a.  When it is desired to alter the thickness of the fluid layer, motor  130   a  is actuated thereby actuating screw rod  160   a  which, depending on the rotation of screw rod  160   a,  will result in sensor  155   a  being moved toward or away from radiation source  175 .  
         [0064]    With reference to FIG. 4, there is illustrated yet another embodiment for altering the thickness of the fluid layer referred to above. In this case, radiation sensor  155  having a face  156  is stationary and radiation source  175  may be moved thereby altering the thickness of the fluid layer between sensor  155  and radiation source  175 . Movement of radiation source  175  may be accomplished by placing a motor  130   b  which is interconnected to a connection block  170  via a screw rod  160   b.  The thickness of the fluid layer between face  156  and radiation source  175  may be altered in the following manner. Motor  130   b  is actuated thereby actuating screw rod  160   b  which, depending on the rotation of screw rod  160   b,  will serve to: (i) retract radiation source  175  and rods  140   b,   145   b  into radiation source housing  115 , or (ii) extend radiation source  175  and rods  140   b,   145   b  from radiation source housing. This has the effect of increasing the thickness of gap A between face  156  and radiation source  175  or, in other words, increasing the thickness of the fluid layer.  
         [0065]    With reference to FIG. 5, there is illustrated an optical radiation sensor device  200  which is an alternate embodiment of the present optical radiation sensor device.  
         [0066]    Thus, device  200  comprises a housing  205  which is substantially fluid-tight. Housing  205  comprises a wall  210  having attached thereto a plate  212 . Disposed in plate  212  is a first radiation sensor  215  and a second radiation sensor  220 . Radiation sensor  215  is maintained in fluid tight engagement with plate  212  via an O-ring  217 . Radiation sensor  220  is maintained in fluid tight engagement with plate  212  via an O-ring  222 .  
         [0067]    A bracket  225  is attached to plate  212  and wall  210  via a bolt  230 . A bolt  235  serves to further secure plate  212  to wall  210 .  
         [0068]    Attached to bracket  225  is a radiation source assembly  240 . Radiation source assembly  240  comprises a radiation source  245  disposed within a radiation transparent protective sleeve  250 . As illustrated, protective sleeve  250  is closed at one end and opened at the other. Disposed in the open end of protective sleeve  250  is a plug  255  against which the open end of protective sleeve  250  abuts. An O-ring  260  is provided in plug  255  a coupling nut  265  and a sleeve  270  are in threaded (or other) engagement such that when coupling nut  265  is tightened, sleeve  270  is biassed against plug  255  which serves to compress O-ring  260  thereby creating a fluid-tight arrangement.  
         [0069]    As illustrated in FIG. 5, first sensor  215  and second sensor  220  have respective faces which are disposed at different distances from radiation source assembly  240 . As will be understood by those of skill in the art, the sensor elements (not shown) disposed with in each of first sensor  215  and second sensor  220  my be detecting radiation at the same or different distance—i.e., it is difference in the respective fluid layer thickness between radiation source  245  and first sensor  215  and between radiation source  245  and second sensor  220  which is important. Thus, device  200  is able to feed back radiation intensity readings at two distances from the radiation source.  
         [0070]    [0070]FIG. 6 illustrates yet a further alternate embodiment to the device illustrated in FIG. 2 for varying the thickness of the fluid layer. In FIGS. 2 and 6, like reference numerals designate like elements. In FIG. 6, the reference numerals for elements which have been moved and/or modified from FIG. 2 carry the suffix “c”.  
         [0071]    Thus, with reference to FIG. 6, the principal change to the embodiment illustrated in FIG. 2 is the presence of a flat panel radiation source  175   c.    
         [0072]    With reference to FIG. 7, there is illustrated a portion of a radiation source module  300 . As will be apparent to those of skill in the art, radiation source module  300  is a of a design similar to that described in any one of U.S. Pat. Nos. 4,482,809, 4,872,980 and 5,006,244 referred to hereinabove. Thus, radiation source module  300  comprises a first support leg  305  and a second support leg  310 . In the illustrated embodiment, second support leg  310  comprises a pair of split plates which are held together to surround a portion of a pair of sleeves  315 , 320 . Each of sleeves  315 , 320  is made of a radiation transparent material such as quartz.  
         [0073]    First support leg  305  further comprises a pair of sockets  325 , 330  welded (or otherwise connected) thereto for receiving the open ends of sleeves  315 , 320 , respectively. A pair of coupling nuts  335 , 340  are used to connect sleeves  315 , 320 , respectively, to sockets  325 , 330 , respectively, in a substantially fluid-tight manner. The specific design and sealing mechanisms are set out in various of the patents referred to above and thus, are within the perview of a person skilled in the art.  
         [0074]    Disposed within sleeve  315  is a radiation source (not shown) such as an ultraviolet lamp. The electrical leads for the radiation source disposed within sleeve  315  are fed through socket  325  and support leg  305  to a source of electricity (not shown).  
         [0075]    Sleeve  320  comprises a radiation sensor  345  which is capable of being moved within sleeve  320  along a guide  350  via a motor  355  or other suitable motive means.  
         [0076]    As illustrated in FIG. 7, sleeves  315 , 320  are in a skewed or substantially non-parallel relationship with respect to each other. Thus, in this relationship, it would be apparent that, when sensor  345  is moved along guide  350 , the fluid layer thickness between sensor  345  and sleeve  315  (and thus the distance from sensor  345  to the radiation source disposed within sleeve  315 ) can be varied, for example between a first fluid layer thickness A and a second fluid layer thickness B. Thus, in this embodiment, motor  355  (or other suitable motive means) alters the fluid layer thickness between the radiation source and the radiation sensor by moving the latter longitudinally with respect to the former in a non-parallel manner.  
         [0077]    In summary, the embodiment illustrated in FIG. 5 comprises the use of a pair of static sensors whereas the embodiments illustrated in FIGS.  1 - 4  and  6  and  7  illustrate the use of a single sensor in a dynamic manner. The common feature is that the embodiments illustrated in FIGS.  1 - 7  provide for obtaining intensity readings from at least two distances from a radiation source in question. These intensity readings each represent a measurement of the radiation detected by a sensor at each (two or more) fluid layer thickness—each thickness is defined by the distance between a sensor and a radiation source. Once this is done, radiation (preferably ultraviolet radiation) transmittance analysis may be achieved as follows.  
         [0078]    Consider a system comprising a single lamp and a single sensor. A fluid layer is provided between the lamp and sensor. The lamp has an intensity at its surface of I o . The thickness of the fluid layer is varied from between thickness x and fluid thickness y. These distances are readily determined by feedback from the motor or other motive means, by measurement, by the design of the optical radiation sensor system and/or by the design of the disinfection system.  
         [0079]    The sensor optics may be designed to accept radiation from a single known plane or location on a source, which means that all light reaching the sensor has travelled substantially the same distance. It is known that the sensor output, S d , for light arriving from a source through fluid thickness d is given by the equation  
         S d =I o k a k g f l f s e −kd   
         [0080]    where I o is the intensity at the lamp, k a  is the gain factor of the sensor, k g  is a geometrical factor, f l is the reduction due to fouling at the lamp sleeve, f s is the reduction due to fouling at the sensor window, and k is the fluid absorbance with units of l/distance. The geometrical factor may be held constant through careful design of the sensor window, apertures and lenses.  
         [0081]    Taking intensity readings at two fluid thicknesses, x and y, and taking the ratio of these two readings results in the following equation:  
           S   x       S   y       =     e     k        (     y   -   x     )                               
 
         [0082]    Note that all factors including lamp output, sensor gain, and fouling have cancelled and do not appear in this equation. The two sensor readings and the fluid thicknesses are known, enabling the calculation of the fluid absorbance or transmittance.  
         [0083]    The foregoing discussion is particularly applicable to the case where a single sensor and single lamp is used (e.g., the embodiments of FIGS.  1 - 4  and  6 - 7 ), but is readily adapted to the case where two sensors are used (e.g., the embodiment of FIG. 5) by calculating S d  for each of the two sensors. The reason for this is that lamp output, sensor gain and/or fouling may not cancel as described in the preceding paragraph.  
         [0084]    Those of skill in the art will also recognize that the Beer-Lambert law, from which the foregoing discussion derives, may also be written in terms of logarithms in base  10 , or directly in terms of transmittance. The general principle behind determining the absorbance or transmittance is the same as described above.  
         [0085]    Those skilled in the art will recognize that, for clarity, various simplifications have been made to facilitate clear presentation of the concepts above. Standard modeling and more sophisticated calculation can be used to account for deviations from the ideal described above.  
         [0086]    While the present invention has been described with reference to preferred and specifically illustrated embodiments, it will of course be understood by those skilled in the arts that various modifications to these preferred and illustrated embodiments may be made without departing from the spirit and scope of the invention. For example, the present invention has been illustrated with reference to a “stand alone” radiation source module which can be used to measure the radiation (preferably ultraviolet radiation) transmittance of fluid in any radiation treatment module and/or system such as one similar in overall design to those described in U.S. Pat. Nos. 4,872,980, 5,006,244, 5,418,370, 5,539,210 and Re36,896. As such, the “stand alone” radiation source module may be a temporarily or permanently installed in the fluid treatment system. Further, it is, of course, possible to incorporate the approach described above with the specifically illustrated embodiments in an actual radiation source module which forms part of the fluid treatment system such as those described in the above-mentioned United States patents. Still further, it is possible to employ the present optical radiation sensor system in a fluid treatment device such as those commercially available from Trojan under the tradenames Trojan UVMax™, Trojan UVSwift™ and Trojan UVLogic™ etc. Still further, while it is most preferred to use the present invention with respect to treatment of liquids such as water, (i.e., wastewater), it is possible to utilize the present optical radiation sensor system in a gas treatment system. Still further, it may be possible, in some applications to omit a protective sleeve (e.g., made out of quartz) for radiation source  175 . Other modifications which do not depart from the spirit and scope of the present invention will be apparent to those with skill in the art.  
         [0087]    All publications, patents and patent applications referred to herein are incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety.