BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a radiation sensing system and, more particularly, but not by way of limitation, to a radiation sensing system with improved resistance to damage from radiation consequential to prolonged operation. 
     2. Description of the Related Art 
     Radiation sensing systems are well known and are used when it is necessary to detect various bands of wavelength across the electromagnetic spectrum. As such, radiation sensing systems are employed to detect ultraviolet radiation associated with drinking water disinfecting units. 
     Generally, irradiating water with sufficient amounts of ultraviolet light will disinfect water for human consumption by eliminating microorganisms from the water. Commercially available drinking water disinfecting units typically employ ultraviolet light emitting lamps disposed within a passageway whereby water flowing through the passageway is disinfected by designated amounts of ultraviolet light emitted from the lamps. 
     Radiation sensing systems are often incorporated in drinking water disinfecting units to monitor the level of ultraviolet radiation emitted from the lamps, thereby enabling the overall efficiency of the water disinfection process to be assessed over a period of time. Unfortunately, however, subjecting radiation sensing systems to continuous and often highly increased radiation levels leads to progressive degradation and irreversible damage in that the radiation sensing system will no longer accurately detect ultraviolet light or may even completely fail. 
     Past attempts to mitigate potential damage from prolonged exposure to radiation have driven the overall cost of radiation sensing systems upward. As such, due to costs associated with repair or replacement, the use of current radiation sensing systems during the intended life span of a drinking water disinfecting unit is unreasonably expensive. For example, radiation sensing systems are unreasonably expensive in that such systems are often constructed entirely of stainless steel, which is well known to be relatively resistant to degradation from radiation. Moreover, radiation sensors within radiation sensing systems are independently and commercially available and are often expensive by design. In particular, well known “can” designs which house photodiodes are unreasonably costly. Costs associated with radiation sensors may also increase depending on the size, shape, and color of a photodiode filter. 
     Accordingly, there is a long felt need for a cost effective radiation sensing system with improved resistance to radiation damage. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a radiation sensing system for detecting electromagnetic radiation and transmitting a sensory signal therefrom includes a body formed from an inexpensive material. The body includes an outlet portion and an inlet portion. The radiation sensing system further includes a radiation sensor inserted substantially into the outlet portion of the body and a plug and inserted substantially into the inlet portion of the body. The plug is formed from material resistant to radiation damage and includes an inlet, an outlet, and a bore therethrough, whereby electromagnetic radiation travels through the plug via the bore. The radiation sensing system still further includes a lens placed over the inlet of the plug and a cap secured over the inlet portion of the body. 
     A method for making the radiation sensing system for detecting electromagnetic radiation and transmitting a sensory signal therefrom includes forming a body from an inexpensive material. As such, the body includes an outlet portion and an inlet portion. The method includes forming a radiation sensor, whereby the radiation sensor is inserted substantially into the outlet portion of the body. 
     A plug is formed from material resistant to radiation damage and then inserted substantially into the inlet portion of the body. The plug includes an inlet and a bore therethrough, whereby electromagnetic radiation travels through the plug via the bore. The preferred bore is threaded for attenuating the electromagnetic radiation traveling therethrough. 
     A lens is placed over the inlet of the plug. A cap is then formed and secured over the inlet portion of the body. In the preferred embodiment, the cap includes a top plate and a side wall extending outwardly from the top plate. 
     Specifically, the cap is secured over the inlet portion of the body by positioning a scraping notch against an aggregation of sealing material in a substantially sold phase to define a first position. The scraping notch is formed from the side wall of the cap and is engaged with the body. The aggregation of sealing material is then deformed. 
     As the cap is inserted further along the body from the first position to a second position, the scraping notch directs the deformed aggregation of sealing material from the first position across a ridge from the body to the second position whereby the aggregation of sealing material is allowed to collect in an annular cavity. The annular cavity is defined by the sidewall of the cap and the body, as the sidewall is placed over the body. Once a sufficient amount is collected in the annular cavity, material from the aggregation of sealing material is allowed to harden within the annular cavity. By abutting against the ridge and the cap, the hardened material wedges the cap to the body and, thus, firmly secures the cap to the body. 
     A radiation sensor is formed by fashioning a photodiode base. A photodiode is then coupled with the photodiode base and photodiode leads are coupled with the photodiode base as well. The photodiode and the photodiode leads are in cooperative engagement, whereby the photodiode detects electromagnetic radiation and emits a sensory signal from the radiation sensor via the photodiode leads. 
     In addition, a filter is formed for eliminating unwanted wavelength bands of electromagnetic radiation traveling therethrough. In the preferred embodiment, the filter is substantially square in shape. As such, the filter is coupled with the photodiode base substantially adjacent to and above the photodiode such that electromagnetic radiation travels through the filter to the photodiode. 
     It is therefore an object of the present invention to provide an apparatus and method of making a cost-effective radiation sensing system with improved resistance to radiation damage. 
     Still other objects, features, and advantages of the present invention will become evident to those skilled in the art in light of the following. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view illustrating a radiation sensing system according to the preferred embodiment featuring a sensing assembly coupled with a signal cable assembly. 
     FIG. 2 is a side view in cross-section illustrating the preferred radiation sensing system. 
     FIG. 3 illustrates a radiation sensor for a radiation sensing system according to the preferred embodiment. 
     FIG. 3 a  is a top elevation view illustrating the radiation sensor. 
     FIG. 3 b  is a cross-section view taken along the lines a, a of FIG. 3 a  illustrating the radiation sensor. 
     FIG. 4 illustrates a radiation sensing unit from a sensing assembly according to the preferred embodiment coupled with a signal cable assembly. 
     FIG. 4 a  is a top view in cross-section taken along the lines b, b illustrating the radiation sensing unit. 
     FIG. 4 b  is side view illustrating the radiation sensing unit coupled with the signal cable assembly. 
     FIG. 4 c  is a bottom view in cross-section taken along the lines b, b illustrating the radiation sensing unit. 
     FIG. 5 is a side view in cross-section illustrating the radiation sensing unit from a sensing assembly according to the preferred embodiment coupled with the signal cable assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As required, detailed embodiments of the present invention are disclosed herein, however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms, the figures are not necessarily to scale, and some features may be exaggerated to show details of particular components or steps. 
     As illustrated in FIG. 1, a radiation sensing system  1  includes a sensing assembly  1 ′ coupled with a signal cable assembly  1 ″. As preferred, ultraviolet light emitting lamps from a drinking water disinfecting unit (not shown) emit light, in a direction shown as arrow  2 , whereby the sensing assembly  1 ′ detects such light. (See FIGS.  1 - 2 ). Accordingly, the sensing assembly  1 ′ transmits a signal across the signal cable assembly  1 ″, shown as directional arrow  3 , to an electronic monitoring/control system (not shown) that assesses the overall efficiency of the water disinfection process. 
     In particular, as shown in FIGS. 1-5, the sensing assembly  1 ′ includes a body  40 . As preferred, the body  40  is generally cylindrical in shape having a central axis as well as an inlet portion and an outlet portion. To significantly reduce cost, the body  40  may be composed of any sufficient material such as plastic. The sensing assembly  1 ′ includes a cap  5  having a top plate and a side wall whereby the side wall extends outwardly from the top plate. In this preferred embodiment, the cap  5  is composed of material resistant to radiation damage, such as stainless steel, which is well known for preventing damage from ultraviolet light. The top plate of the cap  5  defines at least one opening coaxial with the central axis of the body  40  to allow light to enter the interior of the body  40  at the inlet portion. Those skilled in the art will recognize that any sufficient number of openings through the top plate, which will facilitate the entry of light to the interior of the body  40 , may be utilized. 
     The interior surface of the sidewall is adapted to fit around an exterior surface of the body  40  at the inlet portion. (See FIG.  2 ). In particular, as preferred, the interior surface of the sidewall of the cap  5  defines a scraping notch  6  that is engaged with the exterior surface of the body  40 . Moreover, an annular cavity  7  is formed where the exterior surface of the body  40  meets with the interior surface of the sidewall of the cap  5 . A ridge  8  extending from the exterior surface of the body  40  divides the scraping notch  6  from the annular cavity  7 . 
     Accordingly, while in a first position, the cap  5  is placed over the body  40  so that the scraping notch  6  abuts an aggregation of sealing material  9  disposed on the exterior surface of the body  40 . The aggregation of sealing material  9  is formed either by material defining the body  40  or by material placed on the exterior surface of the body  40 . Furthermore, the aggregation of sealing material  9 , as preferred, is composed of any readily deformable material, such as plastic or resin. Thus, while in the first position, the aggregation of sealing material  9  is in a substantially solid phase. 
     The aggregation of sealing material  9  is then allowed to deform, such as through the application of heat or ultrasonic means. As the cap  5  is inserted further along the body  40  from the first position to a second position, the scraping notch  6  directs the deformed aggregation of sealing material  9  from the first position across ridge  8  to the second position whereby the aggregation of sealing material  9  is allowed to collect in the annular cavity  7 . Once a sufficient amount is collected in the annular cavity  7 , the material from the aggregation of sealing material  9  is allowed to harden within the annular cavity  7 . By abutting against the ridge  8  and the cap  5 , the hardened material from the aggregation of sealing material  9  wedges the cap  5  to the body  40  and, thus, firmly secures the cap  5  with the body  40 . In this preferred manner, there in no need for an O-ring seal between a cap and a body of a radiation sensing system for a drinking water disinfecting unit in that O-ring seals in the past often leak water into the body. 
     The sensing assembly  1 ′ includes a lens  15  disposed within the inlet portion of the body  40  and axially aligned with the central axis. The lens  15  allows for electromagnetic radiation to exclusively pass into the interior of the sensing assembly  1 ′ while potentially keeping water or any other foreign material from entering the interior of the sensing assembly  1 ′. The lens  15  may be composed of any electromagnetic radiation transmissive material, such as natural or synthetic quartz. A washer  10  is provided by the sensing assembly  1 ′ between the lens  15  and the cap  5 . The washer  10  defines an opening coaxial with the central axis for allowing electromagnetic radiation to travel between the cap  5  and the lens  15 . In this preferred embodiment, the washer  10  is composed of material that provides little friction against surfaces applied thereon, such as TEFLON. 
     The sensing assembly  1 ′ includes a plug  30  with an inlet and an outlet. At its inlet, the plug  30  is disposed within the inlet portion of the body  40  adjacent the lens  15 . In this preferred embodiment, the plug  30  is adapted to frictionally fit against an interior surface of the body  40  although those skilled in the art will recognize other suitable means for securing the plug  30  within the body  40 . In this preferred embodiment, the plug  30  is threadedly bored therethrough such that a resulting threaded bore is coaxial with the central axis. The threaded bore, in part, attenuates the electromagnetic radiation traveling through the plug  30  as required by the radiation sensing system  1 . It is essential that the plug  30  be composed of a material resistant to radiation damage, such as stainless steel. 
     As such, a plug significantly reduces manufacturing costs for a radiation sensing system in that it is not necessary to construct a body and other component parts of a radiation sensing system from material resistant to radiation damage, which is relatively more costly. Ultimately, to optimally reduce cost, only those components, such as a plug, exposed to electromagnetic radiation as it travels through a sensing assembly should be composed from material resistant to radiation damage. 
     The sensing assembly  1 ′ includes an aperture disk  45  axially aligned with the central axis and disposed within the inlet portion of the body  40  adjacent the outlet of the plug  30 . The aperture disk  45  defines at least one aperture coaxial with the central axis, whereby electromagnetic radiation travels from the plug  30  therethrough. In this preferred embodiment, the aperture disk  45  is composed of material resistant to radiation damage, such as stainless steel. 
     The sensing assembly  1 ′ further includes a radiation sensing unit disposed within the body  40  adjacent the aperture disk  45  such that the aperture disk  45  is between the plug  30  and the radiation sensing unit. Moreover, the radiation sensing unit is axially aligned with the central axis of body  40 . The radiation sensing unit, in turn, includes a radiation sensor whereby electromagnetic radiation travels through the cap  5 , the washer  10 , the lens  15 , the plug  30 , and the aperture disk  45  to the radiation sensor. In this preferred embodiment, the radiation sensor detects ultraviolet radiation and emits a signal across the signal cable assembly  11 ″ to the electronic monitoring/control system thereby enabling the signal to be assessed for the overall efficiency of the water disinfection process. 
     As shown in FIGS. 2-5, the radiation sensing unit includes a spacer  50  with an external spacer portion and an internal spacer portion. The spacer  50  is disposed within the body  40  adjacent the aperture disk  45  such that the external spacer portion is adapted, in part, to frictionally fit against an interior surface of the body  40 , although those skilled in the art will recognize other suitable means for securing the spacer  50  within the body  40 . The internal spacer portion includes an open end and a closed end and defines a collecting chamber  50 ′ therebetween. Thus, electromagnetic radiation is received through the open end from the aperture disk  45 , collected within the collecting chamber  50 ′, and projected on the closed end. The radiation sensor is disposed on the closed end, coaxial with the central axis of the body  40 , to receive electromagnetic radiation from the collecting chamber  50 ′. It should be emphasized that the size and shape of the collecting chamber  50 ′ is configured to optimally project electromagnetic radiation onto the radiation sensor. 
     The radiation sensor includes a photodiode base  53 . (See FIG.  3 ). In this preferred embodiment, the closed end of the internal portion of the spacer  50  defines a recess  50 ″ in which the photodiode base  53  is inserted and secured to, using any suitable means. (See FIG.  2 ). The size and shape of the photodiode base  53  may be configured to optimally receive electromagnetic radiation from the spacer  50 . The radiation sensor includes a photodiode  52  secured to the photodiode base  53  and coaxial with the central axis. The radiation sensor further includes photodiode leads  56  secured to the photodiode base  53  and axially aligned with the central axis. (See FIG.  3 ). Specifically, in this preferred embodiment, the photodiode  52  detects ultraviolet radiation and the photodiode leads  56  transmit a signal from the photodiode  52  across the signal cable assembly  1 ″ to the electronic monitoring/control system. 
     In this preferred embodiment, the photodiode base  53  defines a recess  53 ′ into which the photodiode  52  is inserted and secured. Additionally, as preferred, the photodiode base  53  may include positioning mounts  53 ″ integral with the photodiode base  53 . The radiation sensor includes a filter  51  coaxial with the central axis and secured to the photodiode base  53  via positioning mounts  53 ″ so that the filter  51  is substantially adjacent to and above the photodiode  52 . In operation, electromagnetic radiation passes from the collecting chamber  50 ′, across the filter  51  to the photodiode  52 . Accordingly, integrating the photodiode  52  with the photodiode base  53  significantly reduces manufacturing costs for a radiation sensor in that it is not necessary to purchase an elaborate, commercially available photodiode sensor unit, such as the well known “can” design, which is relatively more costly. 
     The filter  51  eliminates unwanted wavelengths from the incoming electromagnetic radiation so that the photodiode  52  receives only a desired band, such as ultraviolet light, thereby mitigating or eliminating the effects of radiation damage on the radiation sensor. In this preferred embodiment, the filter  51  is composed of any electromagnetic radiation transmissive material sensitive to a particularly desired wavelength band, such as natural or synthetic quartz. In this preferred embodiment, the filter  51  is square shaped which significantly reduces manufacturing costs for a radiation sensor in that it is not necessary to construct a filter with a more elaborate shape, such as a round or an oval shape for example, as in the past which was relatively more costly. 
     Moreover, the radiation sensing unit includes an assembly base  54  axially aligned with the central axis and disposed within the outlet portion of the body  40 . (See FIGS. 2,  4 - 5 ). Additionally, in this preferred embodiment, the assembly base  54  is substantially adjacent to the external portion of the spacer  50  near the closed end. The assembly base  54  defines openings for receiving the photodiode leads  56  therethrough. As such, in this preferred embodiment, the photodiode leads  56  extend from the photodiode base  53 , through the spacer  50 , across the assembly base  54 , and couple with the signal cable assembly  1 ″ via a cable harness  55 . (See FIG.  2 ). The assembly base  54  may include a conductive laminate  54 ′ disposed on the assembly base  54  for enhancing the quality of the signal transmitted between the photodiode leads  56  and the signal cable assembly  1 ″. (See FIG. 4 c ). In particular, the conductive laminate  54 ′ may be positioned at the openings of the assembly base  54  and substantially adjacent to the photodiode leads  56  that pass through the openings. 
     The signal cable assembly  1 ″ for the radiation sensing system  1  includes the cable harness  55  in cooperative engagement with the photodiode leads  56  and includes a cable  60  linked with the cable harness  55  for transmitting a signal from the cable harness to the electronic monitoring/control system. In particular, the cable harness  55  is set in cooperative engagement with the photodiode leads  56  to receive a signal therefrom. Although the preferred signal cable assembly includes a cable and a cable harness, those skilled in the art will recognize other equivalent means for transmitting a signal from the sensing apparatus, such as an antenna. The signal cable assembly  1 ″ is coupled with the sensing assembly  1 ′ in the following preferred manner. The cable harness  55  and the cable  60  are positioned within the outlet portion of the body  40  so that they are each coaxial with the central axis. (See FIG.  2 ). The cable harness  55  and the cable  60  retain their relative positions within the outlet portion in that a filler substrate  57  is introduced into the outlet portion. Besides allowing the signal cable assembly to maintain a desired position within the outlet portion, the filler substrate  57  in this preferred embodiment sufficiently secures the signal cable assembly  1 ″ within the outlet portion. 
     Furthermore, as shown in FIGS. 1 and 2, the radiation sensing system  1  may include O-rings  20 ,  25 , and  35  as well as a securing nut  65 . In particular, the O-ring  20  may be provided between the lens  15  and the plug  30  to create a seal that firmly secures the lens  15  against the washer  5  while potentially keeping water or any other foreign material from entering the interior of the sensing assembly  1 ′. The O-ring  25  may be provided between the plug  30  and the body  40  to enhance the frictional fit of the plug  30  against the interior surface of the body  40 . The O-ring  35  and the securing nut  65  may each be provided to facilitate the integration of a radiation sensing system with an element to be monitored, such as a drinking water disinfecting unit. 
     During operation of the preferred radiation sensing system  1 , ultraviolet light emitting lamps from a drinking water disinfecting unit emit light according to arrow  2 . (See FIG.  2 ). Ultraviolet light travels across the sensing assembly  1 ′ and is detected by the radiation sensor incorporated within the sensing assembly  1 ′. According to directional arrow  3 , the radiation sensor thus transmits a signal across the signal cable assembly  1 ″, coupled with the sensing assembly  1 ′, to an electronic monitoring/control system that assesses the overall efficiency of the water disinfection process. Specifically, ultraviolet light passes through the sensing assembly  1 ′ via an opening provided by the cap  5 , an opening provided by the washer  10 , the lens  15 , a threaded bore of the plug  30 , an aperture provided by the aperture disk  45  to the radiation sensing unit. Within the radiation sensing unit, ultraviolet light travels across the collecting chamber  50 ′ that is configured to optimally project the light onto a radiation sensor of the radiation sensing unit. As such, light within the radiation sensor travels through the filter  51  to the photodiode  52  that detects ultraviolet radiation and transmits a corresponding signal from the photodiode  52  across the photodiode leads  56  to the cable harness  55 . It should also be added that the photodiode leads  56  extend through the radiation sensing unit, from the photodiode base  53 , through the spacer  50 , and across the assembly base  54 , and couple with the signal cable assembly  1 ″ via the cable harness  55 . The signal thus continues its path across the signal cable assembly  1 ″, from the cable harness  55  across the cable  60  linked with the cable harness  55 , to the electronic monitoring/control system. 
     Although the present invention has been described in terms of the foregoing embodiment, such description has been for exemplary purposes only and, as will be apparent to those of ordinary skill in the art, many alternatives, equivalents, and variations of varying degrees will fall within the scope of the present invention. That scope, accordingly, is not to be limited in any respect by the foregoing description, rather, it is defined only by the claims that follow.
A radiation sensing system for detecting electromagnetic radiation and transmitting a sensory signal therefrom includes a body, a radiation sensor inserted substantially into an outlet portion of the body, a plug inserted substantially into an inlet portion of the body, a lens placed over the inlet of the plug, and a cap secured over the inlet portion of the body. A method for making the radiation sensing system includes forming the body from an inexpensive material, forming the radiation sensor and inserting it substantially into the outlet portion of the body, forming the plug from material resistant to radiation damage and inserting it substantially into the inlet portion of the body, placing the lens over the inlet of the plug, and forming a cap and placing it over the inlet portion of the body.