Abstract:
A fiber optic fluid probe is employed in determining characteristics of a fluid or solid dispersed in the fluid into which the probe is immersed. The probe transmits electromagnetic radiation from a source by way of one or more fiber optic fibers and into the fluid, and then senses how the electromagnetic radiation interacts with the fluid. The optical signal returned from the probe, by way of fiber optic cables, is interrogated by an electronic instrument, which correlates the optical response to fluid properties and/or characteristics.

Description:
BACKGROUND OF THE INVENTION 
   (1) Field of the Invention 
   The present invention pertains to a probe that is employed in determining characteristics of a fluid or objects dispersed in the fluid into which the probe is immersed. More specifically, the present invention pertains to a fiber optic probe that transmits electromagnetic radiation typically but not limited to the 200-2200 nanometer region, by way of one or more optic fibers into a fluid, and then senses how the electromagnetic radiation transmitted into the fluid is affected by the fluid or objects in the fluid. By sensing how the transmitted electromagnetic radiation is affected by the fluid, the fiber optic probe enables the determination of certain characteristics and/or properties of the fluid or objects in the fluid. 
   (2) Description of the Related Art 
   In the many different types of industrial facilities that process fluids such as chemical processing facilities or chemical laboratories, petroleum processing facilities, waste water treatment facilities, pharmaceutical processing facilities, etc., it is often desirable to monitor or test the characteristics or properties of the fluids being processed in order to regulate or control the processing of the fluids. For example, in facilities that treat waste water to purify the water, it is desirable to monitor the amounts of chemicals added to the waste water during the purification process in order to ensure that a sufficient amount of the chemicals are added to the waste water to result in its purification, and also to ensure that an excessive amount of the purification chemicals are not added to the waste water which would result in needless expense and potential contamination of the water. 
   In prior art fluid processing facilities, the fluids being processed were often monitored by extracting samples of the fluids or using non-optical based sensors. The samples were then tested to determine the characteristics or properties of the fluids, and thereby evaluate the processing of the fluids. The sampling would require one or more people at the processing facility to physically extract samples of the fluids for analysis. Thus, extracting the samples and then testing the samples would require significant amounts of time during which the fluid processing is continued. If the fluid testing determined that adjustments or changes to the processing were needed, a potentially critical delay would occur before the adjustments would be made. In addition, these testing procedures were at times very hazardous to the human tester, especially where the fluids being processed were potentially corrosive, toxic or explosive liquids or gases. 
   What is needed to overcome the disadvantages of prior art methods of monitoring industrial fluid processing facilities is an apparatus that continuously monitors the characteristics or properties of a fluid in an industrial fluid processing facility, and provides continuous data on the properties of the fluid which would enable real time adjustments in the processing of the fluid to obtain the desired results. 
   SUMMARY OF THE INVENTION 
   The present invention provides several embodiments of fiber optic probes used in monitoring a fluid or solids dispersed in the fluid. The present invention employs fiber optic probes that transmit electromagnetic radiation into a fluid and sense the interaction of the electromagnetic radiation with the fluid or solids suspended in the fluid to enable the determination of properties and characteristics of the fluid or solid in the fluid from the optical response. The fiber optic probes of the invention have novel constructions that employ several of the same component parts in three different types of fiber optic probes. The probes described herein fall into three categories: interaction of the evanescent wave with the fluid or solids dispersed in the fluid using the attenuated total reflection (ATR) method, determination of the transmission of the fluid, and detection of molecular fluorescence from the fluid. All three probes are immersed in the process fluid for in-situ monitoring. 
   The probe constructions enable slight modifications of the probes to adapt them for use in various different types of environments, and to adapt them for use in performing various different types of optic measurements. The ability to use many of the same component parts in constructing the three different types of fiber optic probes reduces manufacturing costs. 
   A first embodiment of the fiber optic probe senses the affect of the tested fluid on evanescent wave or alterations in the optical sensing element total internal reflection. This first probe embodiment is an attenuated total reflectance (ATR) probe. The probe has an elongate, hollow tubular body with opposite proximal and distal ends. One of several different types of protective caps is secured to the body distal end. 
   An optic sensing element, for example a sapphire crystal, is positioned at the probe distal end inside a protective tip guard. Typically the optical sensing crystal has a frustum shape, which results in an ATR element with three sensing surfaces. A proximal end portion of the crystal has a “top hat” like shape, which is received inside the hollow interior of the probe body. A resilient seal, for example a pair of o-ring seals, are positioned around the crystal “top hat” portion. The resilient o-rings provide a seal between the crystal and the interior of the probe body. 
   A cylindrical optical assembly is positioned adjacent to the probe crystal. The optical assembly holds the distal ends of a pair of fiber optic cables adjacent to the proximal end of the probe crystal. The fiber optic cables extend from the distal end of the probe body, through the hollow interior of the probe body, to the proximal end of the probe body. In variant embodiments of the probe, the optical assembly may also incorporate a thermal sensor for monitoring fluid temperature. In addition, a strain gauge may be positioned adjacent the optical assembly for sensing the pressure of the fluid. 
   An internal spacing and compression tube is inserted through the interior of the probe body and abuts against the fiber optic support. A compression ring is screw-threaded into the body proximal end, pushing the spacing tube toward the fiber optic support and the optic crystal, and compressing the resilient seals contacting the optic sensing element. The compression of the resilient seals establishes a seal between the probe exterior environment (the process fluid) and the probe interior at the distal end of the probe. 
   A connector collar is attached to the probe proximal end with the fiber optic cables passing through the connector collar. The proximal ends of the probe fiber optic cables are supported in a positioning plate secured in the interior of the connector collar. The connector collar is adapted for mechanically joining the probe fiber optic cables to lengths of additional fiber optic cables that communicate optical signal from the probe to the testing equipment of the fluid testing facility or lab. The testing equipment determines the characteristics or properties of the tested fluid based on the optical response from the probe. 
   In use of the attenuated total reflectance probe in testing a fluid in which the probe distal end is immersed, electromagnetic radiation is transmitted through one of the fiber optic cables of the probe to the optical sensing crystal. The electromagnetic radiation is reflected off the internal surfaces of the crystal. The characteristics or a property of the fluid or solids dispersed in the fluid in which the probe crystal is immersed affects either evanescent wave or the total internal reflectance of the crystal. The electromagnetic radiation passing through the optical sensing crystal is directed to the other of the fiber optic cable mounted in the optical assembly, which transmits the optical signal from the probe distal end to the additional fiber optic cables that communicate the optical signal from the probe to the testing equipment. The testing equipment uses the optical response to determine the characteristics and/or properties of the tested fluid or solids dispersed in the fluid. 
   The second embodiment of the fiber optic probe is called a transmission probe. This probe embodiment employs the same tubular body, fiber optic cables, internal spacing tube, compression ring, fiber positioning plate, and connector collar as described for the ATR probe. The internal optical assembly is modified to function in conjunction with a “top hat” optical sensing window. In the transmission probe, the optical crystal of the ATR probe is replaced by a retro reflection assembly, typically an optical crystal having two metalized reflective surfaces, and by an optical window with a fluid testing chamber in the probe body between the retro reflection assembly and the optical window. 
   The transmission probe utilizes a measurement specific fluid testing chamber located at the distal end of the tubular body between the optical window and the retro reflection assembly. The fluid testing chamber has a hollow interior. A pair of openings through diametrically opposite sides of the probe body allows the fluid to enter the chamber while the distance between the two optical elements defines the path length of the fluid testing chamber. 
   The retro reflection assembly is positioned inside the distal end of the probe body. In a typical configuration, the retro reflection assembly is a single integrated unit, with a “top hat” cylindrical trapezoidal shape. The angled surfaces are metalized and the “top-hat” portion contacts the process fluid. A resilient seal, for example an o-ring seal, extends around the “top hat” portion of the optical crystal and seals the crystal inside the probe body. 
   The optical window is secured inside the probe body on the opposite side of the fluid testing chamber in relation to the retro reflection assembly. The optical window has optically flat opposite distal and proximal end parallel surfaces. A pair of resilient seals extends around the periphery of the optical window adjacent the distal and proximal end surfaces and seals the optical window in the interior of the tubular body. 
   A modified optical assembly of the previously described embodiment is also employed in the transmission probe. The optical assembly is located in the probe interior and is positioned adjacent the proximal surface of the optical window. As in the previously described embodiment, the optical assembly could also incorporate a thermocouple for sensing the temperature of the process fluid, and/or a strain gauge for sensing the pressure of the process fluid. 
   The internal spacing and compression tube of the previously described ATR probe embodiment is also employed in the transmission probe. The spacing tube is inserted through the interior of the transmission probe body and abuts against the optical assembly. A compression ring, also used in the previously described probe embodiment, is screw-threaded into the tubular body proximal end and pushes the spacing tube toward the optical assembly and the optical window. The spacing tube compresses the resilient seals that extend around the optical window, sealing the optic window in the interior of the tubular body. 
   As in the previously described embodiment, the optical assembly receives and supports the distal ends of a pair of fiber optic cables in the probe interior adjacent to the proximal surface of the optical window. The lengths of the fiber optic cables extend through the probe interior to the proximal end of the probe. 
   A connector collar is attached to the probe body proximal end, as in the previously described embodiment. The proximal ends of the internal fiber optic cables are supported in the same fiber positioning plate of the previously described embodiment. 
   In use of the transmission probe, with the probe immersed in the fluid to be tested, electromagnetic radiation is transmitted through one of the fiber optic cables of the probe to the optical window. The transmitted electromagnetic radiation passes through the optical window, through the fluid contained in the fluid testing chamber, and into the retro retroflection assembly. Electromagnetic radiation leaving the retro reflection assembly passes through the fluid in the testing chamber and through the optical window to the other of the fiber optic cables contained in the probe. The optical signal from the probe is transmitted to fluid testing equipment using additional fiber optic cables. The optical signal is used by the test equipment to determine the characteristics and/or properties of the tested fluid. 
   The third embodiment of the fiber optic fluid probe is called a fluorescence probe. The fluorescence probe makes use of the same tubular body, the spacing and compression tube, the compression ring, and the connector collar of the first described ATR probe embodiment. The fluorescence probe only utilizes a single optical window on the distal end of the probe. Electromagnetic radiation is focused using the optical assembly to a small point a few micrometers from the window surface exciting molecular fluorescence of species present in the process fluid. The same optical assembly used to focus the excitation radiation also collects the fluorescence signal. 
   The fluorescence probe primarily differs from the previously described probe embodiments in that its optical assembly uses the same components to both focus the exciting electromagnetic radiation and collect the fluorescence signal. The optical assembly is cylindrical and has a hollow interior bore with opposite proximal and distal ends. A spherical lens is contained in the optical assembly bore adjacent the fiber optic cable distal ends. One or more electromagnetic radiation receiving fiber optic cable(s) are positioned at the center of the container bore. The distal ends of these receiving optics are positioned adjacent the center of the spherical lens. A plurality of fiber optic cables is arranged around the receiving fiber optic cable(s). The plurality of transmitting fiber optic cables have distal ends that are positioned adjacent the spherical lens at the periphery of the lens. 
   The optical assembly is positioned in the interior bore of the tubular body adjacent to the probe body distal end. A resilient seal, preferably an o-ring seal, extends around the optical assembly adjacent its distal end. The resilient seal engages against the tubular probe body at its distal end. The lengths of the fiber optic-cables extend from the optical assembly through the tubular body interior bore to the proximal end of the tubular probe body. 
   The internal spacing and compression tube is inserted through the interior of the probe body and abuts against the proximal end of the optical assembly. The compression ring is screw-threaded into the probe body proximal end and pushes the spacing tube toward the optical assembly at the probe body distal end. This compresses the resilient seal around the optical assembly, sealing the interior of the probe body. 
   As in the previously described embodiments, the connector collar is attached to the probe proximal end with the internal fiber optic cables passing through the connector collar. The proximal ends of the internal fiber optic cables are supported in the fiber positioning plate secured in the interior of the connector collar. Secondary fiber optic cables transmit the fluorescence signal from the probe to the fluid processing facility for evaluation. 
   In use of the fluorescence probe, electromagnetic radiation is transmitted through the transmitting fiber optic cable to the distal end of the optical assembly where the electromagnetic radiation is focused through a spherical lens. The focused electromagnetic radiation excites molecular fluorescence in the fluid at the probe distal end. The fluorescence signal is collected by the spherical lens and transmitted through the receiving fiber optic cable(s) to their proximal end. The fluorescence signal is transmitted from the probe through additional fiber optic cables to the testing equipment. The testing equipment uses the fluorescence signal to determine the characteristics and/or properties of the tested fluid. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features of the invention are set forth in the following detailed description of the preferred embodiments of the invention and in the drawing Figures wherein: 
       FIG. 1  is a cross-sectional side view of the first embodiment of the fiber optic fluid probe of the invention; 
       FIG. 2  is a view of several of the unassembled component parts of the mechanical framework of the probe of  FIG. 1 ; 
       FIG. 3  is a cross-sectional side view of the optic parts of the probe of  FIG. 1 ; 
       FIG. 4  is a cross-sectional side view of the probe of  FIG. 1  employed with a cleaning cap; 
       FIG. 5  is an additional view of the probe of  FIG. 1 , showing a thermocouple and a strain gauge assembled to the probe; 
       FIGS. 6   a  and  6   b  are a cross-sectional side views of a further embodiment of the fiber optic fluid probe; 
       FIG. 7  is a side view of the probe of  FIG. 6 ; 
       FIG. 8  is a view of several of the unassembled component parts showing the mechanical framework of the probe of  FIG. 6 ; 
       FIG. 9  is an enlarged view of the optic crystal of the probe of  FIG. 6 ; 
       FIG. 10  is an enlarged view of the optic crystal of  FIG. 9 , rotated 90°; 
       FIG. 11  is an enlarged view of the optic window of the probe of  FIG. 6 ; 
       FIG. 12  is a cross-sectional side view of a further embodiment of the fiber optic fluid probe; 
       FIG. 13  is a side view of the optic component parts of the probe of  FIG. 12  removed from the probe; 
       FIGS. 14   a  and  14   b  are an enlarged view of a spherical lens of the  FIG. 12  probe; and, 
       FIGS. 15 and 16  show the probe of  FIG. 4  and an assembly employed to periodically clean the probe. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As explained earlier, the present invention provides several different embodiments of fiber optic probes that are employed in various different types of fluid processing facilities. The probes enable testing of fluids (or solids or semi-solid materials present in the fluid) being processed by the facilities without requiring the time delays associated with random sampling of the fluids and without exposing people at the facilities to potentially harmful fluids being tested. Fiber optic probes of this type are known in the prior art. Examples of these types of probes are disclosed in the U.S. Patents of Ponstingel, et al. U.S. Pat. No. 4,637,730; Ponstingel, et al. U.S. Pat. No. 5,241,368; and Masterson, et al. U.S. Pat. No. 6,043,895. 
   The several embodiments of the fiber optic probes of the invention differ primarily from the probes of the prior art in that the novel constructions of the probes of the invention enable the use of several of the same component parts in the constructions of each of the different probes. The use of the same component parts in the constructions of each of the different probes results in reductions in manufacturing costs due to the reduced inventory of parts required to manufacture the different probe types. The novel constructions of the probes of the invention enable slight modifications to the probes that adapt each probe embodiment for use in a different type of environment and adapt each probe embodiment for use in performing different types of fiber optic testing procedures. Each of the fiber optic probes of the invention is constructed of materials typically employed in constructing such probes, and therefor particular types of materials will not be specified. 
   The construction of a first embodiment of the fiber optic probe  10  is shown in  FIGS. 1-5 . This first embodiment of the fiber optic probe  10  senses the affect of a tested fluid on evanescent wave or alternations in the optical sensing element total internal reflection. The probe shown in  FIGS. 1-5  is an attenuated total reflectance (ATR) fiber optic probe. 
   Referring to  FIGS. 1-3 , the first embodiment of the fiber optic fluid probe  10  is comprised of an elongate tubular body  12 . The body  12  is shown fragmented in  FIG. 1 . It should be understood that the body  12  will have a length that best suits the probe for its intended use. However, in most applications the length of the body  12  will be much longer than that represented by the fragmented probe of  FIG. 1 . In the preferred embodiment, the probe body  12  has a straight length with opposite proximal  14  and distal  16  ends, a cylindrical exterior surface  18  and a cylindrical interior surface  20 . The cylindrical interior surface  20  has a center axis  22  and surrounds a hollow interior bore  24  of the probe. The diameter of the probe body interior bore  24  is consistent along the length of the probe. A majority of the probe body interior surface  20  is smooth, apart from an internally screw-threaded portion  26  of the body interior surface adjacent the body proximal end  14 . 
   A protective tip guard  28  is secured to the body distal end  16 .  FIG. 2  shows the protective tip guard  28  of  FIG. 1 , in addition to a second protective tip guard  28 ′ having a slightly different configuration. Each protective tip guard has an annular shoulder  30 ,  30 ′ that is inserted into the body at the distal end  16 . An exterior seem  32  between the protective tip guard  28  and the body exterior surface  18  is welded and then later polished to provide a smooth continuous surface between the body  12  and the protective tip guard  28 . Openings  34 ,  34 ′ provided in the protective tip guards  28  enable fluid to be tested to flow easily into the interior volumes of the guards. 
   An optic sensing element  36 , for example a sapphire crystal, is positioned at the body distal end inside the protective tip guard  28 . The optic sensing crystal  36  has a distal end portion  38  having the shape of a truncated cone or frustum. This gives the crystal distal end portion  38  a conical surface  40  and a flat, circular surface  42 . The truncated conical shape of the crystal distal end portion  38  defines three reflecting sensing surfaces of the crystal, which will be explained later. As best seen in  FIG. 3 , the optic crystal  36  has a cylindrical, “top hat” like shaped proximal end portion  44 . An annular collar  46  extends around the crystal proximal end portion  44 . The proximal end portion  44  has a flat end surface  48 , and a cylindrical cavity  50  is recessed into the flat end surface  48  and into the interior of the optic crystal  36 . 
   A pair of resilient seals  52 , in the  FIG. 1  embodiment o-ring seals  52 , is mounted on the optic crystal proximal end portion  44  on opposite sides of the annular collar  46 . With the optic crystal  36  positioned inside the interior bore  24  of the probe body  12 , both resilient seals  52  engage and seal against the body interior surface  20 . The distal most resilient seal  52  engages against the cap shoulder  30 , sealing the body interior bore  24  from the exterior environment of the probe. To further the seal the body interior bore  24 , a sealant  54  is applied into the annular groove that surrounds the optic crystal proximal end portion  44  and the interior of the protective cap  28 . 
   There are two versions of the optical insert  56 ,  56 ′ for use with the probe  10  as seen in  FIG. 2 . The optical insert  56 ,  56 ′ is assembled and inserted into the interior bore  24  of the probe body  12  as shown in  FIG. 1 . As seen in  FIG. 2 , the optical insert  56 ,  56 ′ has a cylindrical configuration with a smaller exterior diameter distal end portion  58 ,  58 ′ and a larger exterior diameter proximal end portion  60 ,  60 ′. The distal end portion  58 ,  58 ′ of the optical insert  56 ,  56 ′ is cylindrical and is dimensioned to fit in a tight fit in the optic crystal cavity  50 . A pair of optical assembly holes  62 ,  62 ′ extends through the optical insert  56 ,  56 ′. As seen in  FIG. 2 , the distal end portion  58 ′ of the optical insert  56 ′ have two counter bore holes  57  adjacent and on axis to the optical assembly holes  62 ′ for the mounting of lenses  186 ,  187 . The proximal end portion  60 ,  60 ′ of the optical insert  56 ,  56 ′ is cylindrical and is dimensioned for a tight sliding fit in the body interior surface  20 . 
   Optical insert  56 ′ has two double step counter bore holes  59  adjacent and on axis to the through holes  62 ′ to aid in mounting of the cylindrical distal ends  68 ,  70  of the fiber optics  64 ,  66  and a pair of counter bore holes  63  for mounting of two supporting rods  76  are supplied 90 degrees from the optical assembly holes. 
     FIGS. 1 and 3  show lengths of fiber optic cables  64 ,  66  that are assembled into the body interior bore  24 . One of the fiber optic cables  64  functions in transmitting electromagnetic radiation through the probe to the probe distal end, and the other of the fiber optic cables  66  functions in receiving reflected electromagnetic radiation, as will be explained. The distal ends of the fiber optic cables  64 ,  66  are mounted in cylindrical distal sleeves  68 ,  70  that are positioned in the holes  62 ,  62 ′ of the assembled optical insert  56 ,  56 ′. The distal sleeves  68 ,  70  securely hold the distal ends of the fiber optic cables  64 ,  66  against the optic crystal  36  in the crystal cavity  50 . The lengths of the fiber optic cables  64 ,  66  extend through the probe body interior bore  24  to cylindrical proximal sleeves  72 ,  74  mounted over the proximal ends of the fiber optic cables.  FIG. 3  shows one of two supportive rods  76  and a protective thermal sleeve  78  that are packed into the interior bore  24  of the probe body  12  to protect the lengths of the fiber optic cables  64 ,  66  extending through the interior bore  24  of the probe body  12 . 
   An internal spacing and compression tube  80  is assembled into the interior of the probe body  12 . The tube  80  has a cylindrical length with opposite proximal  82  and distal  84  ends. The tube has a cylindrical exterior surface  86  that is dimensioned to fit in a tight but sliding engagement against the probe body interior surface  20 . The tube exterior surface  86  is smooth across the entire length of the tube. The tube also has a cylindrical interior surface  88  that is smooth through the entire length of the tube. As seen in  FIG. 1 , the length of the tube  80  is determined so that the tube distal end  84  will engage with the optical assembly  56  with the tube proximal end  82  positioned in the internally threaded portion  26  of the probe body  12 . 
   A cylindrical compression ring  90  is screw-threaded into the internally screw-threaded portion  26  of the probe body  12  and engages against the spacing and compression tube proximal end  82 . Screw threading the compression ring  90  into the probe body interior bore  24  moves the spacing and compression tube  80  toward the distal end of the probe. The movement of the tube  80  compresses the resilient o-ring seals  52  that surround the proximal portion of the optic crystal  36 , providing the fluid seal in the interior of the probe body. 
   A connector collar  92  is attached to the probe body proximal end  14 . The connector collar  92  has an externally threaded neck  94  that is screw threaded into the internally screw-threaded portion  26  of the tubular body  12 . The connector collar has a hollow interior bore  96  that receives the proximal end sleeves  72 ,  74  of the fiber optic cables  64 ,  66 , as seen in  FIG. 1 . The connector interior is provided with an internally screw-threaded portion  98  adjacent a proximal end opening  100  of the connector. The proximal end of the connector collar  92  is provided with an external thread  104  adapted to be attached to conduits (not shown) at a fluid processing facility that protect lengths of additional fiber optic cables that communicate the probe  10  with the testing equipment of the facility. 
   A fiber positioning plate  102  is mounted in the interior bore of the connector collar  92  as seen in  FIG. 1 .  FIG. 2  shows the fiber positioning plate  102  which is circular and has two internally threaded holes  106  that pass through the plate.  FIG. 3  shows the assembly of the positioning plate  102  where the holes  106  receive a pair of mechanical connectors  108  which are adjusted and then fixed with a locknut  109 . The connectors  108  receive the proximal sleeves  72 ,  74  of the fiber optic cables  64 ,  66 . The connectors  108  are known in the art and are employed in providing a electromagnetic radiation transmitting coupling between the fiber optic cables  64 ,  66  of the probe and the additional fiber optic cables (not shown) of the fluid testing facility. 
   A connector lock ring  110  is mounted in the interior of the connector collar  92 . The lock ring  110  is circular and has external screw-threading  111  at its outer periphery. The ring external screw-threading  111  is screw-threaded into the connector collar internal screw threading  98 . The ring  110  is screwed up against the positioning plate  102 , thereby locking the positioning plate in its position in the connector collar  92 . 
   In the use of the attenuated total reflectance (ATR) probe  10 , the probe is first immersed in a fluid to be tested as is conventional in the use of probes of this type. The probe  10  communicates with a source of electromagnetic radiation at the testing facility, and the electromagnetic radiation is transmitted through the probe transmitting fiber optic cable  64 . The electromagnetic radiation is emitted from the transmitting fiber optic cable  64  into the optic sensing crystal  36 . As shown in  FIG. 1 , the electromagnetic radiation is directed by means of a lens  187  from the transmitting fiber optic cable  64  toward a portion of the optic sensing crystal conical surface  40 . When two different media with different refractive indices (in this example the optic sensing crystal  36  and the fluid surrounding the optic sensing crystal) contact at an interface (the optic sensing crystal surface), the fluid absorbs some of the electromagnetic radiation energy. In the probe  10  shown in  FIG. 1 , the electromagnetic radiation transmitted into the optic sensing crystal  36  first reflects off a portion of the crystal conical surface  40 , then reflects off the crystal distal end surface  42 , and then again reflects off a portion of the optic sensing crystal conical surface  40  before it is reflected back to the receiving lens  186  for focusing into the receiving fiber optic cable  66 . The affect of the fluid on absorbing some of the electromagnetic radiation reflected off the optic sensing crystal surfaces is determined by the testing facility. In this way, characteristics and/or properties of the fluid in which the probe  10  is immersed can be determined. 
   In addition to the above, the probe  10  of  FIG. 1  can also be employed in detecting the build up of scale inside a fluid container by detecting the rate of scale build up on the surface of the optic sensing crystal  36 . By monitoring the rate of scale build up, a controlled amount of scale inhibitor can be delivered into the fluid processing system to control the scale. 
     FIG. 4  shows the fiber optic probe  10  having a cleaning cap  112  attached to the probe body distal end  16  in lieu of the protective tip guard  28  shown in  FIG. 1 . The cleaning cap  112  also protects the optic sensing crystal  36 . The cap  112  has a pair of diametrically opposed openings  114  that permit the flow of fluid to be tested to enter the cap interior and surround the optic sensing crystal  36 . The cleaning cap  112  primarily differs from the previously described protective tip guard  28  in that it is provided with a distal extension  116 . A pair of annular grooves  118  is formed in the exterior surface of the extension  116 . A pair of resilient seals  120 , in the example shown in  FIG. 4  o-ring seals  120 , is assembled into the pair of annular grooves  118 . 
   In use of the probe  10  illustrated in  FIGS. 15 and 16 , the probe is typically inserted through a conduit  222  that intersects with a wall  224  of a container containing the fluid to be tested. The conduit has a valve assembly  226  that is opened to allow passage of the probe through the conduit. The probe  10  is inserted through the conduit  222  and opened valve  226  so that the optic sensing crystal  36  projects into the interior volume of the container containing the fluid. 
   The cleaning cap  112  enables periodic cleaning of the surfaces of the optic sensing crystal  36 . When cleaning is desired, the probe  10  is retracted in the conduit  222  so that the optic sensing crystal  36  is withdrawn out of the interior of the fluid container and into the conduit. The probe  10  is retracted to the extent that the pair of resilient seals  120  on the cleaning cap  112  is also received in the conduit and is positioned on the opposite side of the valve  226  from the container  224 . The pair of resilient seals  120  seals the optic probe  10  from the interior of the container containing the fluid being tested. The valve  226  is closed, sealing the probe  10  in the conduit  222 . The conduit  222  is provided with a port  228  behind the valve  226  through which cleansing materials can be injected. The cleansing materials are injected into the conduit  222  and enter through the openings  114  of the cleansing cap  112  and surround the exterior surfaces of the optic sensing crystal  36 . In this way, the cleansing material cleans the exterior surfaces of the optic sensing crystal  36 . When the cleaning operation is completed, the valve  226  is opened and the probe  10  is again extended through the conduit so that the cleaning cap  112  and the optic sensing crystal  36  are again extended into the interior of the fluid container where the exterior surfaces of the optic sensing crystal  36  are again exposed to the fluid being tested. 
     FIG. 5  shows a further embodiment of the probe  10  of  FIG. 1 . In the  FIG. 5  probe a thermal couple  122  is provided in the optic sensing crystal  36 . The thermal couple  122  senses the temperature of the fluid being tested and provides signals through a conductor  124  to the fluid processing facility testing equipment. In addition, the embodiment of the probe  10  shown in  FIG. 5  is provided with a strain gauge  126 . The strain gauge  126  is positioned just behind the optical assembly  56 . The strain gauge  126  is compressed by the pressure of the fluid acting on the optic sensing crystal  36 . The compression of the strain gauge  126  produces a signal sent through the strain gauge conductor  128  to the testing equipment of the fluid processing facility, providing a measurement of the fluid pressure. 
     FIGS. 6-11  show a second embodiment of the fiber optic probe  130  of the invention. The probe shown in  FIGS. 6-11  is a transmission probe. One of the beneficial features provided by the novel constructions of the probes of the invention is that each of the different embodiments of the probes, although employed in different methods of testing fluids, makes use of many of the same component parts. Thus, the constructions of each of the probes enables the use of many of the same component parts in each probe which results in a reduction in the costs involved in manufacturing the probes. Because several of the component parts of the transmission probe  130  are the same as those employed in the ATR probe  10 , these component parts will not be described in detail. In drawing  FIGS. 6-11  the component parts of the transmission probe that are common to those of the ATR probe are identified by the same reference numerals employed in identifying the parts of the ATR probe, with the reference numeral being followed by a prime (′). 
   The transmission probe  130  employs the same tubular body  12 ′, a slightly different optical assembly  56 ″, the same transmitting and receiving fiber optic cables (not shown), the same internal spacing and compression tube  80 ′, the same compression ring  90 ′, the same connector collar  92 ′, the same positioning plate  102 ′, and the same connector lock ring  110 ′ as the ATR probe  10 . In the transmission probe  130 , the optic sensing crystal  36  of the ATR probe  10  is replaced by a retro reflection assembly  132  that is configured to have two reflective surfaces  134 ,  136 . In addition, an optical window  138  is also assembled into the probe interior. The transmission probe  130  is also provided with a different protective tip guard  140  than that employed on the ATR probe  10 . 
   Referring to  FIGS. 6-8 , the protective tip guard  140  is cylindrical and has a cylindrical interior surface  142  surrounding a hollow interior bore  144  of the guard. The guard  140  extends for a short length between opposite proximal  146  and distal  148  ends of the guard. The guard interior bore  144  extends entirely through the length of the guard between its proximal  146  and distal  148  ends. The interior surface  142  of the guard is provided with internal screw threading  154  adjacent the guard distal end  148 . The guard is provided with an annular shoulder  150  at its proximal end  146 . The annular shoulder  150  fits into the distal end of the probe tubular body  12 ′. The guard  140  is secured to the probe tubular body  12 ′ in the same manner as the previously described embodiment. A pair of openings  152  is provided in diametrically opposite sides of the guard. 
   A positioning plate  156  having an outer periphery with external screw threading  158  is screw threaded into the internal screw threading  154  of the protective tip guard  140 . A stopper  160  having external screw threading  162  is also screw threaded into the internal screw threading  154  at the guard distal end  148 . The stopper  160  has an annular groove that receives a resilient seal, for example an o-ring seal  164 . The resilient seal  164  engages against the interior surface of the protective tip guard  140  with the stopper  160  attached to the guard, sealing closed the guard distal end  148 . 
   The retro reflection assembly  132  is positioned in the interior of the guard  140  with a distal end surface of the assembly abutting against the V-block support disk  155 . The V-block disk  155  transfers the sealing pressure evenly to the crystal  132  from the positioning plate  156  as shown in  FIG. 6 . The retro reflection assembly  132  is shown enlarged in drawing  FIGS. 9 and 10 . As seen in  FIGS. 9 and 10 , the assembly  132  has a pair of reflective surfaces  134 ,  136  that are oriented at an angle relative to each other. The assembly  132  also has a cylindrical proximal portion  166  with a flat, circular end surface  168 . A resilient seal, preferably an o-ring seal  170  extends around the assembly proximal portion  166  and engages against the interior surface of the protective tip guard  140  providing a seal between the assembly and the tip guard. As seen in  FIG. 6 , the positioning of the retro reflection assembly  132  in the interior of the tip guard  140  positions the crystal flat end surface  168  on one side of a hollow interior chamber of the guard as defined between the opposed openings  152  of the cap. 
   An enlarged view of the optical window  138  removed from the probe is shown in  FIG. 11 . The window  138  has a “top hat” shape with a cylindrical distal portion  172  with a circular, flat end surface  174 . The window has a larger, cylindrical proximal portion  176  with a circular, flat end surface  178 . A resilient seal  180 , for example an o-ring seal, is positioned around the window distal end portion  172 . The seal  180  engages against the protective tip guard annular shoulder  150 , sealing the interior bore of the probe body  12 ′ from the test chamber in the guard interior bore  144  between the pair of guard openings  152 . An additional resilient seal, for example an o-ring seal  182 , is positioned on the opposite side of the window distal end portion  172 . This additional seal  182  is compressed by the optical assembly  56 ″, providing an additional seal in the interior of the probe body  12 ′. 
   As in the previously described embodiment, the transmission probe  130  could also be provided with a thermal couple for sensing temperature of a fluid, and/or a strain gauge for sensing the pressure of the fluid. 
   In use of the transmission probe  130 , with the probe distal end immersed in the fluid to be tested, electromagnetic radiation is transmitted through the transmitting fiber optic cable  64 ′ to the optical window  138 . The electromagnetic radiation passes through the optical window  138  and through the fluid contained in the interior bore testing chamber  144  between the protective tip guard openings  152 . The electromagnetic radiation passes through the fluid in the testing chamber and then passes into the retro reflection assembly  132 . The electromagnetic radiation reflects off the first surface  134  of the assembly, and then reflects off the second surface  136  of the assembly. The reflected electromagnetic radiation then again passes through the fluid in the testing chamber of the protective tip guard  140 . The electromagnetic radiation then passes through the optical window  138  and is received by the receiving fiber optic cable  66 ′. The electromagnetic radiation is then transmitted by the receiving fiber optic cable  66 ′ to the testing equipment of the fluid processing facility where the optical signal is used to determine the characteristics and/or properties of the tested fluid. 
     FIGS. 12 and 13  show a third embodiment of the fiber optic probe  190 . The embodiment of the fiber optic probe  190  shown in  FIGS. 12 and 13  is a fluorescence probe. The fluorescence probe  190  makes use of many of the same component parts of the previously described embodiments of the probes, and the same component parts of the ATR probe are identified by the same reference numerals followed by a double prime (″). 
   The fluorescence probe  190  makes use of the same tubular body  12 ″, the same protective tip guards  28 ,  28 ′ and  28 ″, the same internal spacing and compression tube  80 ″, the same compression ring  90 ″, basically the same connector collar  92 ″ (the connector collar is elongated from those of the previous embodiments), the same positioning plate  102 ″, and the same connector lock ring  110 ″. 
   The fluorescence probe  190  primarily differs form the previously described embodiments in that it is provided with an optical assembly  192  that uses a plurality of fiber optic cables  214  with a common lens  208  to both focus the exciting electromagnetic radiation and to collect the fluorescence signal. All the fiber optic cables in the assembly can be configured to either transmit or receive electromagnetic radiation. As seen in  FIGS. 12 and 13 , the optical assembly  192  is cylindrical and has a length with opposite proximal  194  and distal  196  ends. A hollow interior counter bore  198  extends through the length of the optical assembly  192 . A portion of the optical assembly interior bore is surrounded by internal screw threading  200  adjacent the assembly proximal end  194 . The distal end of the optical assembly  196  has a small opening to expose an optic window  220  to the fluid. A sealant is used to fill the space surrounding the protruding window within the counter bore  188 . The assembly exterior surface has opposite distal  202  and proximal  204  end portions. The proximal end portion  204  has a slightly larger exterior diameter dimension than the distal end portion  202 . A resilient seal, for example an o-ring seal  206 , extends around the optical assembly distal end portion  202 . As seen in  FIG. 12 , the optical assembly  192  is inserted in the interior of the probe body  12 ″ with the resilient seal  206  engaging against the protective tip guard annular shoulder  30 ,  30 ′, and  30 ″. The spacing and compression tube  80 ″ compresses the resilient seal  206 , establishing a seal between the exterior environment of the probe  190  and the interior of the probe body  12 ″. 
   The interior counter bore  198  of the optical assembly  192  contains the fiber optic cluster assembly adjacent to a gasket  219 , an optic window  220  and a resilient seal  221  in the distal end  196  of the assembly. For further sealing a sealant may be used to fill the space between the counter bore  188  and the protruding optic window  220 . A spacer ring  212  is press fit into the sleeve  210  and holds the lens  208  against the rim  211  as seen in  FIG. 14   a . In  FIG. 12 , an externally threaded ring  213  holds the completed sleeve  210  assembly into the proximal end  194  of the optical assembly  192 . 
   The sleeve  210  holds together the distal end of the cluster of fiber optic cables  214  adjacent the center of the spherical lens  208 . The electromagnetic radiation receiving fiber optic cable(s) extends through the interior of the probe bore  12 ″ to a proximal end  216  of the fiber optic cable(s) secured in the connector collar  92 ″. 
   A plurality of electromagnetic radiation transmitting fiber optic cables is arranged around the receiving fiber optic cable(s) of the cluster  214 . The transmitting fiber optic cables have distal ends  217  arranged around the receiving fiber optic cable(s) distal end  215 . The electromagnetic radiation transmitting fiber optic cables extend through the interior of the probe body  12 ″ to proximal ends  218  of the fiber optic cables positioned in the connector collar  92 ″. 
   As in the previously described embodiments, the fluorescence probe  190  could also be provided with a thermal couple and/or a strain gauge. In addition, the fluorescence probe  190  could be provided with a cleaning cap for periodic cleaning of the surface of the optic window  220 . 
   In use of the fluorescence probe  190 , electromagnetic radiation is transmitted through the transmitting fiber optic cables to the distal ends  217  of the cables where the electromagnetic radiation is transmitted through the spherical lens  208 . The transmitted electromagnetic radiation fluoresces in the fluid at the probe distal end. The fluorescence of the electromagnetic radiation is received by the receiving fiber optic cable(s) distal end  215 , and the electromagnetic radiation is transmitted though the receiving fiber optic cable(s) to the proximal end  216 . The received electromagnetic radiation is transmitted from the probe  190  to the testing equipment of the fluid processing facility. The testing equipment uses the reflected fluorescence electromagnetic radiation to determine the characteristics and/or properties of the tested fluid. 
   Although the fiber optic probe of the invention has been described above by referring to three specific embodiments of the invention, it should be understood that modifications and variations could be made to the invention without departing from the intended scope of protection provided by the following claims: