Patent Publication Number: US-7212009-B2

Title: Fluid detection cable

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a divisional of U.S. patent application Ser. No. 11/000,636 entitled “Fluid Detection Cable” by Donald M. Raymond, Donald A. Raymond and Jeffrey W. Whitham, filed Nov. 30, 2004, which claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 60/526,203 entitled “Fluid Detection Cable”, filed Dec. 1, 2003, the entire disclosure of which is hereby specifically incorporated by reference for all that it discloses and teaches. 

   BACKGROUND OF THE INVENTION 
   a. Field of the Invention 
   The present invention pertains generally to fluid detection and, more particularly, to the use of cables for detection of the presence of fluids. 
   b. Background of the Invention 
   Cabled sensors and cables have been used in the detection of the presence of fluids. In many applications, it is desirable not only to detect the presence of fluids, but also to determine the location of a fluid. 
   The ruggedness and durability of the cable used is important. For example, in industrial, commercial or residential applications, movement of people or objects above or near the cables may result in breakage or disconnection of the cable. Hence, fluid detection cables need to be sufficiently rugged to minimize potential breakages or disconnections. 
   In some cases, placement of a structure or object near or on top of the cable may cause a malfunction of the fluid detection system either with a false detection when no fluid is present, or failure to detect a fluid when one is present. Some existing cables have a disadvantage when used around metal structures or other conductive materials since contact with conductive surfaces can form a short circuit across the sensing leads of the cables which can cause a false alarm in the fluid detection system. In existing fluid detection cables, certain conductive elements (e.g. conductors) of the cable must make contact with the fluid to detect the presence of the fluid. In some cases the construction of the cable is such that sensing leads are not disposed to immediately sense small amounts of fluid. A fluid may be present, but the level of the fluid may be too low to be in contact with the sensing leads. Hence, these cables do not detect fluids until the level of the fluid is sufficiently high. 
   Fluid detection cables that are too big or that have the wrong shape, may also negatively impact the site where they are installed. For example, many round fluid detection cables have a diameter of ¼ inch or more. Installation of such cables below a carpet or other floor covering creates a trip hazard or at a minimum an unsightly bump. 
   Another problem with previous fluid detection cables is that the size of the cable makes it difficult to install the cable in tight places. For example, in the construction of a building, it may be desirable to install fluid detection cables directly adjacent to or along the bottom of a wall or in other tight spaces. Existing cables are too large, or the wrong shape, and thus are not suitable for use. 
   Installation of fluid detection systems with cables into environments where equipment, floor coverings, or other structures are already in place may be difficult or impossible, due to the size and the shape of the cable, and the size and shape of the connecters. 
   Another problem with existing fluid detection cables is that when a leak or other contact of the cable with fluid occurs, it is necessary to dry the cable in order for the system to properly function again. Many cables are constructed with hygroscopic materials, i.e., materials that absorb moisture, or act as a wick to draw in and retain fluids. Drying of these cables to return them to the normally dry state required for fluid detection may require removal of the cable from the installed site followed by heating or blowing the cable for a period of time until the moisture has evaporated. Removal and reinstallation of the cable from an installed site may be difficult and time consuming. In some situations the cable can be dried without removing it, but the drying process is time consuming and may damage the cable by heating it. Also, some fluid detection cables require a fastener to secure the cable. Such fasteners must be placed at regular intervals. Other fluid detection cables must be glued to the floor. Such fastening of the cables with certain shapes and sizes may be necessary for proper function, but it makes removal and drying time consuming and difficult. When the cable is fastened to a surface, the use of large or expensive connectors at the ends of the cable makes cutting the connectors from the ends of the cable in order to remove it by pulling it through the fasteners difficult and costly. 
   Further, existing fluid detection cables and connectors require expensive materials. As a result, the cost of a fluid detection system is high, especially for residential applications or other applications requiring relatively low cost. 
   SUMMARY OF THE INVENTION 
   The invention may therefore comprise a method of detecting water comprising: placing a water detection cable comprising two sensing leads, the sensing leads having a center conductor surrounded by a porous non-conductive polymer, the porous non-conductive polymer providing an insulating layer surrounding the conductor, adjacent to a surface that is to be monitored for the presence of water, and monitoring the water detection cable. 
   The invention may further comprise a method of detecting water comprising: providing a water detection cable that has two sensing leads, the sensing leads having a center conductor that is at least partially surrounded by a conductive polymer and a non-conductive polymer shielding that partially surrounds the conductive polymer, the non-conductive polymer shielding having at least one water transmission path that permits water to electrically contact the conductive polymer; installing the water detection cable adjacent to a surface that is to be monitored for the presence of water; and providing a monitor for monitoring the water detection cable. 
   The invention may further comprise a method of detecting water comprising: providing a water detection cable that has two sensing leads, the sensing leads having a center resistive conductor that is at least partially surrounded by a non-conductive polymer shielding, the non-conductive polymer shielding having at least one water transmission path that permits water to electrically contact the conductor; installing the water detection cable adjacent to a surface that is to be monitored for the presence of water; and providing a monitor for monitoring the water detection cable. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of a four-conductor flat fluid detection cable. 
       FIG. 2  is an oblique view of a four-conductor flat fluid detection cable. 
       FIG. 3A  is a cross-sectional view of a flat fluid detection cable with a porous non-conductive polymer coating. 
       FIG. 3B  is a cross-sectional view of another embodiment of a flat fluid detection cable with a porous non-conductive polymer coating. 
       FIG. 3C  is an oblique view of a flat fluid detection cable with a porous non-conductive polymer coating. 
       FIG. 4A  is an oblique view of another embodiment of a flat fluid detection cable without a porous non-conductive polymer coating. 
       FIG. 4B  is an oblique view of another embodiment of a flat fluid detection cable without a porous non-conductive polymer coating. 
       FIG. 4C  is an oblique view of another embodiment of a flat fluid detection cable with a porous non-conductive polymer cover on at least one sensing lead. 
       FIG. 5A  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 5B  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 6A  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 6B  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 7A  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 7B  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 8A  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 8B  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 8C  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 9A  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 9B  is a cross-sectional view of another embodiment of a flat fluid detection cable. 
       FIG. 10A  is a cross-sectional view of another embodiment of a fluid detection cable. 
       FIG. 10B  is a cross-sectional view of another embodiment of a fluid detection cable. 
       FIG. 11A  is a cross-sectional view of a multi-conductor embodiment of a fluid detection cable. 
       FIG. 11  B is a cross-sectional view of a multi-conductor embodiment of a fluid detection cable. 
       FIG. 12  illustrates the manner that a fluid detection cable may be connected to a transmitter through the use of low-cost plugs and receptacles. 
       FIG. 13  illustrates the use of a fluid detection cable with plugs, receptacles and control system with transmitter for connecting to a remote monitor. 
       FIG. 14  illustrates the use of a fluid detection cable in a particular application. 
       FIG. 15  illustrates the use of a fluid detection cable in another application. 
       FIG. 16  illustrates the use of a fluid detection cable in another application. 
       FIG. 17  illustrates the use of a fluid detection cable in another application. 
       FIG. 18  illustrates the use of a fluid detection cable in another application that includes monitoring leaks from drainage pipes. 
       FIG. 19  illustrates the use of a fluid detection cable beneath a carpet or other floor coverings. 
       FIG. 20  illustrates the manner in which a loop can be formed with a tight turning radius of the fluid detection cable maintaining flat contact against a surface to be monitored for fluid detection. 
       FIG. 21  illustrates the manner in which a bend can be made in the fluid detection cable for use in an application that requires a tight turning radius. 
       FIG. 22  illustrates a type of fastener that can be used to fasten a fluid detection cable to a surface. 
       FIG. 23  illustrates another type of fastener that can be used to fasten a fluid detection cable to a surface. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a cross-sectional view of a four-conductor flat fluid detection cable  100 . The fluid detection cable  100  includes a first sensing lead  124 . The first sensing lead has a center conductor  110 . The center conductor  110  may be made of copper, stainless steel or other conductive materials including non-metallic conductors, such as graphite fibers. Alternatively, the center conductor may be a resistive material, such as Chromel or other conductive materials that have additives that increase the resistance. Resistive conductors enable fluid detection systems to determine the location of a fluid as described below. Resistive conductors are available from Bob Martin Company, South El Monte, Calif. Resistive conductors that have a resistance in the range of 2 to 3 ohms per foot are well suited for use in systems that use resistance to determine the location of a fluid. However, resistive conductors with any desired resistance may be used. 
   The center conductor  110 , shown in  FIG. 1 , is surrounded by a conductive polymer  112 . The conductive polymer  112  is non-porous and protects the center conductor  110  from corrosion in the presence of corrosive fluids. The conductive polymer  112  is coated with a porous non-conductive polymer  114 . The porosity of the porous non-conductive polymer  114  allows water and other fluids to penetrate and make electrical or ionic contact with the conductive polymer  112 . The porous non-conductive polymer  114  also insulates the inner conductive polymer  112  from making electrical contact with non-liquid conductive surfaces such as pipes, conductive computer room subfloors, appliances or other conductive surfaces. Porous polymer jackets for conductors can be obtained from Northwire, Inc., Osceola, Wis. and Putnam Plastics, Dayville, Conn. Porous non-conductive polymers provide a fluid transmission path that permits fluid to pass through the non-conductive polymer and to make electrical contact or ionic contact with a conductive polymer or a conductor that is covered the porous non-conductive polymer and at the same time the porous non-conductive polymer does not permit solids to make electrical contact with a conductive polymer or conductor that is surrounded by the porous non-conductive polymer. In other embodiments, the fluid transmission path through the non-conductive polymer may be long continuous slots in a trough formed by the physical structure of the non-conductive polymer, so that the fluid transmission path permits fluids, but not solids, to pass. In the various embodiments of the invention, each sensing lead may have a porous fluid transmission path or a structural fluid transmission path or both. The fluid transmission path for one sensing lead may differ from the fluid transmission path of other sensing leads. 
   Adjacent and joined to the first sensing lead  124 , is a first monitor lead  126 . The first monitor lead  126  has a center conductor  102  that may be made of copper or other conductive materials. Conductors used in either the sensing leads or the monitor leads may be solid or stranded. The conductors may be made of other conductive materials including conductive polymers, graphite fibers or any conductive material. The center conductor  102  is surrounded by a non-conductive polymer  104 . The non-conductive polymer  104  acts as a protective insulator for conductor  102 . Adjacent and joined to the first monitor lead  126  is a second monitor lead  128 . The second monitor lead  128  has a center conductor  106  that is surrounded by a non-conductive polymer  108 . Joined and adjacent to the second monitor lead  128  is a second sensing lead  122 . The second sensing lead has a center conductor  116  that is surrounded by a conductive polymer  118 . The conductive polymer  118  is surrounded by a porous non-conductive polymer  120 . Within this disclosure, polymers may be any flexible plastic-like or rubber-like material. All polymer coatings or structures in the drawings herein are non-porous unless specifically labeled as porous. Polymers used in the various embodiments may be made of halogen free material to meet environmental requirements in certain applications. 
   One of the advantages that various embodiments of fluid detection cable provide over existing cables is that these embodiments provide a fluid detection cable that does not short circuit or falsely sense a fluid when in contact with non-liquid conductive surfaces and at the same time is flat or has a small diameter, can be formed into a tight loop, and can be installed in, or removed from, tight places. The thickness of the various polymer coatings and the size of the conductors of some embodiments of the fluid detection cable, as described, are exemplary only, and should not be considered as limiting the claims. In one embodiment, the thickness of the first conductive polymer layer may be, e.g., 5 mils thick and the outer porous non-conductive polymer coating may be, e.g., 5 mils thick. The non-conductive polymer used to insulate the monitor leads may be, e.g., 20 mil thick. The conductors may be e.g., about 22 gauge or 24 gauge. Using conductors and coatings of the thickness mentioned allows the height of the cable to be approximately 0.1 inches or less. The sensing leads and the monitor leads can be arranged in a flat, ribbon configuration, which facilitates the flatness of the fluid detection cable. Arrangements in which a monitor lead or a spacing member is disposed between the sensing leads eliminates the need to ensure that any fluid in the porous polymer jacket of the sensing leads is dried following contact with a fluid. The monitor leads or spacing member may be wiped dry and thus eliminate the presence of conductive fluids between the sensing leads. However, any desired arrangement and/or order can be used in accordance with the invention. For example, other embodiments of the invention may use at least two sensing leads each with an exterior non-conductive polymer coating that is porous that provides a fluid transmission path. Fluid transmission paths may also be structurally formed in the non-conductive polymer coating. Other embodiments may have one or more monitor leads joined in an arrangement with the sensing leads that have a porous non-conductive outer jacket. 
   Fluid detection cables are used to detect the presence of leaks or other fluids using a variety of electronic means, some of which are described in U.S. Pat. No. 6,144,209, Raymond et al., which is specifically incorporated herein by reference for all that it discloses and teaches. Examples of the types of systems frequently used to monitor and detect leaks or other fluids are zone systems, distance read (also called direct read) and Time-Domain Reflectometry (herein referred to as TDR) systems. In zone systems, the length of the cable may range from a few feet to more than 1000 feet. Further, the conductors of the sensing leads need not be resistive in a zone system. The location of the fluid in a zone system is determined by zone rather than trying to pinpoint a distance from the controller to the point of contact of the fluid with the cable. In distance read systems (sometimes referred to as direct read systems), a sensing lead with a resistive center conductor is electrically connected to a monitor lead at the end of the cable farthest from the controller. The sensing lead and the monitor lead at the end of the cable nearest, or internal to, the controller may be connected to a constant current source in the controller. A second sensing lead is connected to a second monitor lead at the end of the cable farthest from the controller and the ends of the sensing lead and the monitor lead nearest, or internal to, the controller may be connected to a voltage measuring device. Presence of water or other conductive fluid forms a conductive path from the sensing lead connected to the current source to the sensing lead connected to the voltage-measuring device. The distance from the controller to the point of contact of the sensing leads with a fluid can be calculated by deriving the resistance required to produce the measured voltage and calculating the length of cable that has the required resistance. Monitor leads may be used as a conductive path for connecting the sensing leads to the controller. Further, monitor leads may be used as a means of checking the electrical continuity of a cable. Monitor leads and sensor leads may also be used to carry other desired electrical signals such as communication and power signals to distributed electronic devices. 
     FIG. 2  is an oblique view of the fluid detection cable  100  described in  FIG. 1 . The fluid detection cable  100  includes a first sensing lead  124  that has a center conductor  110 . The center conductor  110  is surrounded by a conductive polymer  112 . The conductive polymer is coated with a porous non-conductive polymer  114 . Adjacent and joined to the first sensing lead  124  is a first monitor lead  126  that has a center conductor  102 . The center conductor  102  is surrounded with a non-conductive polymer  104 . Adjacent and joined to the first monitor lead  126  is a second monitor lead  128  that has a center conductor  106 . The center conductor  106  is surrounded with a non-conductive polymer  108 . Adjacent and joined to the second monitor lead  128  is a second sensing lead  122 . The second sensing lead  122  has a center conductor  116 . The center conductor  116  is surrounded by a conductive polymer  118 . The conductive polymer  118  is concentrically surrounded with a porous non-conductive polymer  120 . 
     FIG. 3A  is a cross-sectional view of a four-conductor flat fluid detection cable  300  with a non-conductive polymer outer shielding  322  that forms a trough that is capable of collecting fluid. The fluid detection cable  300  includes a first sensing lead  324 . The first sensing lead has a center conductor  310 . The center conductor  310  may be made of copper, stainless steel or other conductive materials as disclosed above with respect to  FIG. 1 . Alternatively the center conductor may be of resistive material as described above. The center conductor  310  is at least partially surrounded by a conductive polymer  312 . The conductive polymer  312  is non-porous and protects the center conductor  310  from corrosion in the presence of corrosive fluids. The conductive polymer  312  is coated with a porous non-conductive polymer  314 . The porosity of the porous non-conductive polymer  314  allows water and other fluids to penetrate and make electrical or ionic contact with the conductive polymer  312 . The porous non-conductive polymer  314  also insulates the inner conductive polymer  312  from making electrical contact with non-liquid surfaces that are conductive such as pipes, conductive computer room subfloors, appliances or other conductive surfaces. Adjacent and joined to the first sensing lead  324  is a first monitor lead  330 . The first monitor lead  330  has a center conductor  302  that may be made of copper or other conductive materials. The center conductor  302  is surrounded by a non-conductive polymer  304 . The non-conductive polymer  304  acts as a protective insulator for conductor  302 . Adjacent and joined to the first monitor lead  330  is a second monitor lead  328 . The second monitor lead  328  has a center conductor  306  that is surrounded by a non-conductive polymer  308 . The two monitor leads  330  and  328  are covered by a non-porous non-conductive cover  326 . The non-porous non-conductive polymer cover  326  dries easily when wiped thus facilitating quick and easy drying of an installed cable or an uninstalled cable. Adjacent and joined to the second monitor lead  328  is a second sensing lead  332 . The second sensing lead has a center conductor  316  that is at least partially surrounded by a conductive polymer  318 . The conductive polymer  318  is surrounded by a porous non-conductive polymer  320 . Adjacent and joined to the sensing leads  324  and  332  and the monitor leads  330  and  328 , is a non-porous non-conductive polymer outer shielding  322 . Any desired arrangement of the sensing leads  324  and  332  and the monitor leads  330  and  328  may be made as disclosed above with respect to  FIG. 1 . 
     FIG. 3A  further illustrates an optional adhesive strip  334  that is joined to the non-conductive outer shielding  322 . The adhesive strip may be used to attach the fluid detection cable  300  to a surface. A similar adhesive strip may be used with any of the embodiments of the invention. 
   In the fluid detection systems described herein and in other systems, the non-conductive porous polymer outer coating of the sensing leads protects the cable from short circuits when the cable contacts non-liquid surfaces that are conductive. The non-porous non-conductive shielding  322  forms a trough that is capable of collecting fluids. 
   For detecting conductive fluids such as water, the fluid detection cable  300  may be used with a Time-Domain Reflectometry fluid detection system, herein referred to as a TDR system. Additional details relating to the use of the fluid detection cable in TDR systems are described below. 
     FIG. 3B  illustrates another embodiment of a four-conductor flat fluid detection cable. The fluid detection cable  340  is similar to the fluid detection cable  300  disclosed in  FIG. 3A , but has certain structural differences.  FIG. 3B  discloses monitor leads that are surrounded by a non-porous non-conductive polymer outer shielding  352 .  FIG. 3B  further illustrates that the conductor  344  of first sensing lead  342  may be partially surrounded by a non-porous, non-conductive polymer outer shielding  352 . Further, conductor  344  of the first sensing lead  342  may be partially surrounded with a first layer of conductive polymer  346  and a second layer of porous, non-conductive polymer  348 , which provides a conductive path for water or other fluids to conductor  344 . A second sensing lead  350  may be made substantially the same as the first sensing lead  342 . 
     FIG. 3C  illustrates an oblique view of a four-conductor flat fluid detection cable  300 , illustrated in  FIG. 3A , having a non-conductive polymer outer shielding  322  that forms a trough that is capable of collecting fluid. The fluid detection cable  300  includes a first sensing lead  324 . The first sensing lead has a center conductor  310 . The center conductor  310  may be made of copper, stainless steel or other conductive materials as disclosed above with respect to  FIG. 1 . Alternatively, the center conductor may be of resistive material as described above. The center conductor  310  is at least partially surrounded by a conductive polymer  312 . The conductive polymer  312  is coated with a porous non-conductive polymer  314 . Adjacent and joined to the first sensing lead  324  is a first monitor lead  330 . The first monitor lead  330  has a center conductor  302  that may be made of copper or other conductive materials. The center conductor  302  is surrounded by a non-conductive polymer  304 . The non-conductive polymer  304  acts as a protective insulator for conductor  302 . Adjacent and joined to the first monitor lead  330  is a second monitor lead  328 . The second monitor lead  328  has a center conductor  306  that is surrounded by a non-conductive polymer  308 . The two monitor leads  330  and  328  are covered by a non-porous non-conductive cover  326 . The non-porous non-conductive polymer cover  326  dries easily when wiped thus facilitating quick and easy drying of an installed cable or an uninstalled cable. Adjacent and joined to the second monitor lead  328  is a second sensing lead  332 . The second sensing lead has a center conductor  316  that is at least partially surrounded by a conductive polymer  318 . The conductive polymer  318  is surrounded by a porous non-conductive polymer  320 . Adjacent and joined to the sensing leads  324  and  332  and the monitor leads  330  and  328  is a non-porous non-conductive polymer outer shielding  322 . The non-porous non-conductive shielding  322  forms a trough that is capable of collecting fluids.  FIG. 3C  further illustrates an adhesive strip  334  that is joined to the non-conductive outer shielding  322 . 
     FIG. 4A  illustrates an oblique view of another embodiment of a four-conductor fluid detection cable  400 . In the embodiment of  FIG. 4A , fluid detection cable  400  includes a first sensing lead  402  that has a center conductor  430  that is surrounded by a non-porous conductive polymer. The center conductor  430  may be a low resistance conductor or a resistive conductor as described above with respect to  FIG. 1 . A second sensing lead  404  may be made substantially the same as first sensing lead  402 . Fluid detection cable  400  further includes a first monitor lead  406  that has a conductor  432 . Conductor  432  may be a solid conductor or a stranded conductor. Adjacent to first monitor lead  406  is a second monitor lead  408  that may be constructed substantially the same as the first monitor lead. The monitor leads  406 ,  408  are positioned between the sensing leads  402 ,  404  so that the cable may be easily wiped to remove fluid. However, other embodiments with the various sensing and monitor leads in different positions with respect to each other are within the scope of the invention. 
   Monitor leads  406 ,  408  are surrounded by non-conductive polymer outer shielding  410 . Non-conductive polymer outer shielding  410  provides a convenient structure for supporting the sensing leads  402 ,  404  and monitor leads  406 ,  408 . In the embodiment of  FIG. 4A , the non-conductive polymer outer shielding  410  has a substantially planar bottom-side to which an optional adhesive strip  434  may be attached. Non-conductive polymer outer shielding  410  has two sides which are inclined planes  416 ,  418  as showing in  FIG. 4A . Inclined planes  416 ,  418  permit fluid to easily climb the sides of non-conductive polymer outer shielding  410  and enter troughs  420 ,  422 ,  424 ,  426 . Non-conductive polymer covers  412 ,  414  cover a portion of sensing leads  402 ,  404  so that a fluid transmission path is provided through which fluid can pass to make electrical contact with a portion of the sensing leads  402 ,  404 . Thus, sensing leads  402 ,  404  are partially exposed to any fluid that collects in troughs  420 ,  422 ,  424 , and  426  through small gaps or slots between the non-conductive polymer outer shielding  410  and the non-conductive polymer covers  412 ,  414 . Long continuous slots, i.e. fluid transmission paths, are formed between the non-conductive polymer shielding  410  and the covers  412 ,  414  at the bottom of troughs  420 ,  422 ,  424 ,  426 . The fluid transmission paths allow fluids to electrically contact the sensing leads and, at the same time, the structure of the non-conductive polymer prevents conductive solids from electrically contacting the sensing leads  402 ,  404 . The use of fluid transmission paths that are long continuous slots in the bottom of troughs  420 ,  422 ,  424 ,  426 , formed between the non-conductive polymer outer shielding  410  and non-conductive polymer covers  412 ,  414  allows both the non-conductive polymer outer shielding  410  and the non-conductive polymer covers  412 ,  414  to be made of a broad range of materials that do not need to be porous and which may be manufactured using a broad ranges of inexpensive manufacturing methods, such as, for example, extrusion, coating, spraying or any method that is desired for use with the selected non-conductive polymer. 
   In some applications it may be desirable to detect fluids only when the level of the fluid is high enough to climb the inclined planes  416 ,  418  and enter troughs  420 ,  422 ,  424 ,  426 . In other applications, a lower level of fluid may be detected by placing fluid detection cable  400  face-down, i.e. with troughs  420 ,  422 ,  424 ,  426  facing down. 
     FIG. 4B  illustrates an oblique view of a flat fluid detection cable  440 . In the embodiment of  FIG. 4B , fluid detection cable  440  includes a first sensing lead  442  that has a center conductor  470  that is surrounded by a non-porous conductive polymer  468 . The center conductor  470  may be a low resistance conductor or a resistive conductor as described above with respect to  FIG. 1 . A second sensing lead  444  may be made substantially the same as first sensing lead  442 . 
   Non-conductive polymer outer shielding  450  provides a convenient structure for supporting the sensing leads  442 ,  444 . In the embodiment of  FIG. 4B , the non-conductive polymer outer shielding  450  has a substantially planar bottom-side to which an optional adhesive strip  474  may be attached. Non-conductive polymer outer shielding  450  has two sides which are inclined planes  456 ,  458  as shown in  FIG. 4B . Inclined planes  456 ,  458  permit fluid to easily climb the sides of non-conductive polymer outer shielding  450  and enter troughs  460 ,  462 ,  464 ,  466 . Non-conductive polymer covers  452 ,  454  cover a portion of sensing leads  442 ,  444  so that a fluid transmission path is provided through which fluid can pass to make electrical contact with a portion of the sensing leads  442 ,  444 . Thus, sensing leads  442 ,  444  are partially exposed to any fluid that collects in troughs  460 ,  462 ,  464 , and  466  through small gaps or slots between the non-conductive polymer outer shielding  450  and the non-conductive polymer covers  452 ,  454 . Long continuous slots, i.e. fluid transmission paths, are formed between the non-conductive polymer shielding  450  and the covers  452 ,  454  at the bottom of troughs  460 ,  462 ,  464 ,  466 . The fluid transmission paths allow fluids to electrically contact the sensing leads and, at the same time, the structure of the non-conductive polymer prevents conductive solids from electrically contacting the sensing leads  442 ,  444 . The use of fluid transmission paths that are long continuous slots in the bottom of troughs  460 ,  462 ,  464 ,  466 , formed between the non-conductive polymer outer shielding  450  and non-conductive polymer covers  452 ,  454  allows both the non-conductive polymer outer shielding  450  and the non-conductive polymer covers  452 ,  454  to be made of a broad range of materials that do not need to be porous and which may be manufactured using a broad ranges of inexpensive manufacturing methods, such as, for example, extrusion, coating, spraying or any method that is desired for use with the selected non-conductive polymer. 
   In some applications it may be desirable to detect fluids only when the level of the fluid is high enough to climb the inclined planes  456 ,  458  and enter troughs  460 ,  462 ,  464 ,  466 . In other applications, a lower level of fluid may be detected by placing fluid detection cable  440  face-down, i.e. with troughs  460 ,  462 ,  464 ,  466  facing down. 
     FIG. 4C  illustrates an oblique view of a flat fluid detection cable  441 . In the embodiment of  FIG. 4C , at least one of the sensing leads such as sensing lead  445  is at least partially covered with a porous non-conductive polymer cover such as porous non-conductive polymer cover  455 . Fluid detection cable  441  includes a first sensing lead  443  that has a center conductor  471  that is surrounded by a non-porous conductive polymer  469 . The center conductor  471  may be a low resistance conductor or a resistive conductor as described above with respect to  FIG. 1 . A second sensing lead  445  may be made substantially the same as first sensing lead  443  except that a porous non-conductive polymer cover  445  may be used. The porosity of porous non-conductive polymer cover  445  provides a fluid transmission path that allows electrical contact of a fluid with sensing lead  445 . 
   Non-conductive polymer outer shielding  451  provides a convenient structure for supporting the sensing leads  443 ,  445 . In the embodiment of  FIG. 4C , the non-conductive polymer outer shielding  451  has a substantially planar bottom-side to which an optional adhesive strip  475  may be attached. Non-conductive polymer outer shielding  451  has two sides which are inclined planes  457 ,  459  as shown in  FIG. 4C . Inclined planes  457 ,  459  permit fluid to easily climb the sides of non-conductive polymer outer shielding  451  and enter troughs  461 ,  463 ,  465 ,  467 . Non-conductive polymer cover  453  covera a portion of sensing leads  443  so that a fluid transmission path is provided through which fluid can pass to make electrical contact with a portion of the sensing lead  443 . Thus, sensing leads  443 ,  445  are able to be in electrical contact with fluid that collects in troughs  461 ,  463 ,  465 , and  467  through the fluid transmission path formed between the non-conductive polymer outer shielding  451  and the non-conductive polymer covers  453  or through the fluid transmission path through the porous non-conductive polymer cover  455 . The fluid transmission paths allow fluids to electrically contact the sensing leads and, at the same time, the structure of the non-conductive polymer prevents conductive solids from electrically contacting the sensing leads  443 ,  445 . 
   In some applications it may be desirable to detect fluids only when the level of the fluid is high enough to climb the inclined planes  457 ,  459  and enter troughs  461 ,  463 ,  465 ,  467 . In other applications, a lower level of fluid may be detected by placing fluid detection cable  441  face-down, i.e. with troughs  461 ,  463 ,  465 ,  467  facing down. 
     FIG. 5A  is a cross-sectional view of a fluid detection cable  500 . The fluid detection cable  500  includes a first sensing lead  512 . The first sensing lead has a center conductor  508  that is surrounded by a porous non-conductive polymer  510 . The porous non-conductive polymer  510  electrically insulates the conductor  508  from electrical contact with non-liquid surfaces that are conductive but the porosity allows electrical or ionic contact with fluids. Adjacent and joined to the first sensing lead  512  is non-conductive polymer spacing member  506  of any desired width. The surface of the non-conductive polymer spacing member  506  may be wiped dry to remove fluids. Adjacent and joined to the non-conductive polymer spacing member is a second sensing lead  514 . The second sensing lead has a center conductor  502 . The conductor  502  is surrounded with a porous non-conductive polymer  504 . The fluid detection cable  500  is flat and relatively inexpensive to manufacture. Hence it is especially well suited for residential and other applications requiring low cost. 
     FIG. 5B  illustrates a fluid detection cable  520 . Fluid detection cable  520  is similar to fluid detection cable  500  disclosed in  FIG. 5A  but has certain structural differences. A first sensing lead  534  has a center conductor  522  that is adjacent and joined to a non-conductive polymer spacing member  526  of any desired width. A porous non-conductive polymer  524  at least partially surrounds the conductor  522 . A second sensing lead  532  may be made substantially the same as the first sensing lead  534 . 
     FIG. 6A  is a cross-sectional view of a fluid detection cable  600 . The fluid detection cable  600  includes a first sensing lead  616 . The first sensing lead  616  has a center conductor  602  that is surrounded by a conductive polymer  604 . The conductive polymer  604  protects the conductor  602  from corrosion when the sensing lead  616  is in the presence of a corrosive fluid. The conductive polymer  604  is encircled with a porous non-conductive polymer  606 . The porous non-conductive polymer  606  insulates the conductive polymer  604  from electrical contact with non-liquid surfaces that are conductive but the porosity allows electrical or ionic contact with fluids. Adjacent and joined to the first sensing lead  616  is non-conductive polymer spacing member  608  of any desired width. The surface of the non-conductive polymer spacing member  608  may be wiped dry to remove fluids. Adjacent and joined to the non-conductive polymer spacing member is a second sensing lead  618 . The second sensing lead has a center conductor  610 . The conductor  610  is surrounded with a conductive polymer  612  that is encircled with a porous non-conductive polymer  614 . The fluid detection cable  604  is flat and relatively inexpensive to manufacture. This embodiment also protects the conductors  602  and  610  from corrosive fluids. Hence, it is especially well suited for residential and other applications requiring low cost where corrosive fluids may be present. 
     FIG. 6B  illustrates a fluid detection cable  620 . Fluid detection cable  620  is similar to fluid detection cable  600  disclosed in  FIG. 6A  but has certain structural differences. A first sensing lead  638  has a center conductor  630  that is adjacent and joined to a non-conductive polymer spacing member  628  of any desired width. A first layer conductive polymer  632  at least partially surrounds the conductor  630 . A second layer porous non-conductive polymer  634  at least partially surrounds the first layer conductive polymer  632 . A second sensing lead  636  may be made substantially the same as the first sensing lead  638 . 
     FIG. 7A  is a cross-sectional view of a fluid detection cable  700 . The fluid detection cable  700  includes a first sensing lead  716 . The first sensing lead  716  has a center conductor  702  that is surrounded by a conductive polymer  704 . The conductive polymer  704  protects the conductor  702  from corrosion when the sensing lead  716  is in the presence of a corrosive fluid. The conductive polymer  704  is encircled with a porous non-conductive polymer  706 . The porous non-conductive polymer  706  insulates the conductive polymer  704  from electrical contact with non-liquid surfaces that are conductive and at the same time the porosity allows electrical or ionic contact with fluids. Adjacent and joined to the first sensing lead  716  is non-conductive polymer spacing member  708 . The surface of the non-conductive polymer spacing member  708  may be wiped dry to remove fluids. One or more monitor conductors, such as monitor conductor  710  may be embedded within the non-conductive polymer spacing member. The embodiment of  FIG. 7A , as well as any of the embodiments that are shown as including monitor wires, can be constructed without any monitor wires, if desired. Adjacent and joined to the non-conductive polymer spacing member is a second sensing lead  718 . The second sensing lead has a center conductor  712 . The conductor  712  is surrounded with a conductive polymer  720  that is encircled with a porous non-conductive polymer  714 . The fluid detection cable  704  is flat and relatively inexpensive to manufacture. This embodiment also protects the conductors  702  and  712  from corrosive fluids. The monitor conductor  710  may be connected to one of the sensing conductors to provide a return path for a current. Alternatively, the monitor conductor  710  may be connected to another electrical signal which if disconnected signals a break in electrical continuity of the cable. 
     FIG. 7B  illustrates a fluid detection cable  730 . Fluid detection cable  730  is similar to fluid detection cable  700  disclosed in  FIG. 7A  but has certain structural differences. A first sensing lead  748  has a center conductor  742  that is adjacent and joined to a non-conductive polymer spacing member  738 . A first layer conductive polymer  750  at least partially surrounds the conductor  742 . A second layer porous non-conductive polymer  744  at least partially surrounds the first layer conductive polymer  750 . A second sensing lead  746  may be made substantially the same as the first sensing lead  748 . 
     FIG. 8A  is a cross-sectional view of a fluid detection cable  800 . The fluid detection cable  800  includes a first sensing lead  816  that has a center conductor  802 . The center conductor  802  is surrounded by a non-porous non-conductive polymer  804 . The non-porous non-conductive polymer inhibits electrical contact of fluid and solids with conductor  802  but allows a fluid to be detected by sensing a change in the dielectric at the location of the fluid. The first sensing lead  816  is adjacent and joined to a non-conductive polymer spacing member  806  of any desired width. The non-conductive polymer spacing member  806  may optionally include one or more additional monitor conductors, such as monitor conductor  814 . Adjacent and joined to the non-conductive polymer spacing member  806  is a second sensing lead  818 . The second sensing lead  818  includes a center conductor  808  that is surrounded by a conductive polymer  810  that protects the conductor  808  from corrosion. The conductive polymer  810  is encircled by a porous non-conductive polymer  812 . The non-conductive polymer is made to form a trough  820  that is capable of collecting fluid. The trough allows fluids to be collected between the second sensing lead  818  and the first sensing lead  816 . The trough enhances the effectiveness of the fluid detection cable  800  when used with TDR systems as disclosed below with respect to  FIG. 9A . 
     FIG. 8B  illustrates a fluid detection cable  830 . Fluid detection cable  830  is similar to fluid detection cable  800 , disclosed in  FIG. 8A  but has certain structural differences. A first sensing lead  848  has a center conductor  838  that is adjacent and joined to a non-conductive polymer spacing member  836  of any desired width. A first layer conductive polymer  840  at least partially surrounds the conductor  838 . A second layer porous non-conductive polymer  842  at least partially surrounds the first layer conductive polymer  840 . A second sensing lead  852  has a conductor  832  that is surrounded by a non-porous non-conductive polymer spacing member  836 . The non-conductive polymer spacing member  836  forms a trough  850  that is capable of collecting fluid. The non-porous non-conductive polymer inhibits electrical contact of fluid and solids with conductor  832  but allows a fluid to be detected by sensing a change in the dielectric at the location of the fluid. 
     FIG. 8C  illustrates a fluid detection cable  860 . Fluid detection cable  860  is similar to fluid detection cable  830 , disclosed in  FIG. 8B  but has certain structural differences. A first sensing lead  878  has a center conductor  858  that is adjacent and joined to a non-conductive polymer spacing member  866  of any desired width. A first layer conductive polymer  870  at least partially surrounds the conductor  858 . A second layer non-conductive polymer cover  872  at least partially covers the first layer conductive polymer  870 . A least one structural fluid transmission path for fluid to electrically contact conductive polymer  870  is provided between non-conductive polymer cover  872  and non-porous non-conductive polymer spacing member  866 . A second sensing lead  882  has a conductor  862  that is surrounded by a non-porous non-conductive polymer spacing member  866 . The non-conductive polymer spacing member  866  forms a trough  880  that is capable of collecting fluid. The non-porous non-conductive polymer  866  inhibits electrical contact of fluid and solids with conductor  862  but allows a fluid to be detected by sensing a change in the dielectric at the location of the fluid. 
     FIG. 9A  is a cross-sectional view of a fluid detection cable  900 . The fluid detection cable  900  includes a first sensing lead  920  that has a center conductor  902  that is surrounded by a conductive polymer  904 . The conductive polymer  904  in encircled in a porous non-conductive polymer  906 . The sensing lead  920  is adjacent and joined to a non-conductive polymer spacing member  908 . The non-conductive polymer spacing member  908  may optionally include one or more monitor conductors  910  and  912 . Adjacent and joined to the non-conductive polymer spacing member  908  is a second sensing lead  922 . The second sensing lead  902  includes a center conductor  914  that is surrounded by a conductive polymer  916  that protects the conductor  914  from corrosion. The conductive polymer  916  is surrounded by a porous non-conductive polymer  918 . The first sensing lead  920  and the second sensing lead  922  are joined to the non-conductive polymer spacing member  908  and disposed to form a trough  924  that is capable of collecting fluid. 
   In a Time Domain Reflectometry fluid detection system, the presence of water or other fluids causes a change in the dielectric constant at that location of the cable. This change in dielectric constant is measured by sending a signal into a first sensing lead, which may be any of the sensing leads  922  and  920 , of the cable and measuring the reflected signal over a period of time. A second sensing lead acts as a ground reference. The reflected signal measurement at each point in time corresponds to a location along the length of the cable. If water or other fluids are in contact with the sensing leads of the cable, a reflection corresponding to the location of the liquid will occur. No reflection will occur from locations where no fluid is present. In a TDR system, the fluid need not be conductive, but the reflection corresponding to a location in contact with a conductive fluid will have a different amplitude and otherwise differ from a reflection resulting from a non-conductive fluid. The sensitivity of the TDR system to the change in dielectric constant is enhanced by an electrically conductive path from the first sense lead  922  to the second sense lead  920 . Further, the formation of a trough  924 , or fluid collecting channel, by the non-porous non-conductive polymer spacing member  908 , enhances the sensitivity of the TDR fluid detection system by increasing the amount of fluid and associated dielectric constant in electrical contact with the two sensing leads  922  and  920 . In other words, the fluid acts as a dielectric material that causes a reflected wave in the detection cable. The delay of the reflected pulse is indicative of the location of the fluid. The amplitude of the reflected wave is indicative of the type of fluid. For example, water contains more ions than petrochemicals. Water will cause a larger reflected pulse, as explained below. Presence of an electrical short circuit between the sense leads of a fluid detection cable, such as by unintentional contact with a metal object, such as the side of a cooler or dishwasher, will cause a false detection in prior art liquid detection cables. Use of a porous non-conductive polymer  906  and  918  surrounding the sense leads  922  and  920  of the fluid detection cable prevents false detections caused by short circuiting of the sense leads as a result of an unintentional contact with a non-liquid conductive surface. 
   In another application, various embodiments of the fluid detection cable may be used to detect the presence of a fluid in a dissimilar fluid. The presence of conductive fluids that are in contact with sensing leads of various embodiments of the fluid detection cable can be distinguished from the presence of non-conductive fluids by measuring the amplitude of the reflections. Reflections from locations in contact with conductive fluids will have a reflection with greater amplitude than reflections from locations in contact with non-conductive fluids. For example, in a fuel tank, a thin layer of water may accumulate at the bottom of the tank. The fluid detection cable  900  may be disposed at the bottom of the tank and because of the flatness of the cable and the trough  924  formed by the non-conductive polymer spacing member  908  and the sensing leads  920  and  922 , a quantity of water will be collected in the trough  924 . The water can be sensed, using a conductive and resistive measurement, or using a TDR system to measure a different dielectric constant at the location of the cable that is in contact with water. Other embodiments of the fluid detection cable as disclosed above may be used with a TDR system. 
     FIG. 9B  illustrates a fluid detection cable  930 . Fluid detection cable  930  is similar to fluid detection cable  900  disclosed in  FIG. 9A  but has certain structural differences. A first sensing lead  950  has a center conductor  932  that is adjacent and joined to a non-conductive polymer spacing member  938 . A first layer conductive polymer  934  at least partially surrounds the conductor  932 . A second layer porous non-conductive polymer  936  at least partially surrounds the first layer conductive polymer  934 . A second sensing lead  952  may be made substantially the same as the first sensing lead  950 . 
     FIG. 10A  is a cross-sectional view of a non-planar embodiment of a fluid detection cable  1000 . The fluid detection cable includes a first sensing lead  1004 . The first sensing lead  1004  has a center conductor  1016  surrounded by a conductive polymer  1018 . The conductive polymer  1018  is surrounded by a porous non-conductive polymer  1020 . The fluid detection cable further includes a two-conductor monitor lead  1002 . The two-conductor monitor lead  1002  has a first conductor  1012  and a second conductor  1010 . The first conductor  1012  and the second conductor  1010  are electrically insulated and surrounded by a non-conductive polymer  1014 . Disposed at a midpoint of the two-conductor monitor lead  1002  and joined to the two-conductor monitor lead  1002  is the first sensing lead  1004 . A second sensing lead  1008  that is constructed substantially the same as the first sensing lead  1004  is joined to the two-conductor monitor lead on the side opposite from the first sensing lead  1004 . The porous non-conductive polymer on the sensing leads protects the sensing leads from electrical contact with non-liquid surfaces that are conductive. For example, the fluid detection cable could be used inside a metallic conduit. 
     FIG. 10B  illustrates a fluid detection cable  1030 . Fluid detection cable  1030  is similar to fluid detection cable  1000  disclosed in  FIG. 10A  but has certain structural differences. A first sensing lead  1034  has a center conductor  1036 . A first layer conductive polymer  1048  at least partially surrounds the conductor  1036 . A second layer porous non-conductive polymer  1040  at least partially surrounds the first layer conductive polymer  1048 . The first sensing lead  1034  is adjacent and joined to a non-conductive polymer spacing member  1044 . A second sensing lead  1038  may be made substantially the same as the first sensing lead  1034 . 
     FIG. 11A  illustrates another embodiment of a fluid detection cable  1100 . Fluid detection cable  1100  includes a first sensing lead  1104 . The first sensing lead has a center conductor  1112  that is surrounded by a conductive polymer  1114 . The conductive polymer  1114  is surrounded by a porous non-conductive polymer  1116 . The fluid detection cable further includes a second sensing lead  1102  constructed substantially the same as the first sensing lead. The fluid detection cable  1100  includes a plurality of monitor leads. A first monitor lead  1106  has a center conductor  1108  surrounded by a non-conductive polymer  1110 . Other monitor leads are constructed substantially the same as the first monitor lead. The first sensing lead  1104  and the second sensing lead  1102  are joined to the monitor leads. 
   In larger systems, low resistance conductors may comprise a leader cable to electrically connect the fluid detection cable to the control system. The leader cable is not used to detect the presence of fluids and therefore need only have low resistance conductive members (e.g. conductors). In such systems it may be desirable to have multiple sections of fluid detection cable. Such a system may use multiple leader cables connected to multiple fluid detection cables. The system may first determine the section or sections of cable that are in contact with fluid. Then the distance from the controller to the fluid may be determined as disclosed above. Multiple sections of fluid detection cable  1100  may be connected so that some of the monitor leads of a first section of cable act as leader cables for a second section of cable. The monitor leads of the second section of cable act as leader cables for subsequent sections of cable. Thus, instead of installing multiple fluid detection cables with multiple leader cables, a single fluid detection cable  1100  may be installed in sections, with the multiple monitor leads acting as leader cables to subsequent sections. The fluid detection cable  1100  with multiple monitor leads may be constructed in a non-planar embodiment as shown in  FIG. 1100 , or the sensing leads and monitor leads may be joined to form a flat cable. In either case the outer coating of porous polymer surrounding the sensing leads protects the cable from false alarms through an electrical short circuit of the sensing leads when in contact with a conductive non-liquid surface. 
     FIG. 11B  illustrates a fluid detection cable  1120 . Fluid detection cable  1120  is similar to fluid detection cable  1100  disclosed in  FIG. 11A  but has certain structural differences. A first sensing lead  1124  has a center conductor  1132  that is adjacent and joined to a non-conductive polymer  1130 . A first layer conductive polymer  1134  at least partially surrounds the conductor  1132 . A second layer porous non-conductive polymer  1136  at least partially surrounds the first layer conductive polymer  1134 . A second sensing lead  1122  may be made substantially the same as the first sensing lead  1032 . 
     FIG. 12  illustrates the use a fluid detection cable  1216  in multiple cable system. A detector  1200  may have a plurality of jacks including a first jack  1206 . A fluid detection cable  1216  has a connector  1218  that is plugged into jack  1206  of the detector. The detector may have a second jack  1204 . Another cable that is a first leader cable  1214  may be plugged into a second jack  1204 . The detector may have a third jack  1202 . A second leader cable  1210  that has a first connector  1208  may be plugged into the third jack  1202  and a second connector  1212  that may be used to connect to another fluid detection cable or a leader cable. The jacks provide a simple and easy manner of connecting fluid detection cables and leader cables to the detector  1200 . 
     FIG. 13  illustrates the use of a fluid detection cable in a wireless system  1300 . The wireless system  1300  has a detector/transmitter  1302  connected to an antenna  1309  and one or more jacks including a first jack  1308  and a second jack  1310 . A fluid detection cable  1304  that has a connector  1306  may be plugged into the first jack  1308  of the detector/transmitter  1302 . The wireless system  1300  may have a second cable which may be a leader cable  1314  that has a first connector  1312 . The first connector  1312  may be plugged into the second jack  1310  of the detector/transmitter  1302 . The leader cable  1314  has a second connector  1316  that may be used to connect to another fluid detection cable or a leader cable. The wireless system further includes a monitor  1318  that has an antenna  1320  and is connected to the detector/transmitter via a wireless connection  1322 . A wireless system may be well suited for applications where installation of a leader cable is not desired such as, for example, in finished buildings where no provision has been made to install additional cables. 
     FIG. 14  illustrates the use of a fluid detection cable  1402  in a commercial or industrial application with a cooler  1400 . It may be desirable to attach the fluid detection cable to the cooler  1400  at a height so that the fluid detection cable is not in contact with a floor which may get wet during mopping. Thus, a level of water high enough to potentially damage the cooler or other equipment will be detected, but a thin film of water from cleaning, mopping, or condensation will not cause a false alarm. 
     FIG. 15  illustrates using a fluid detection cable  1504  in an application near a water heater  1500 . The application may include a detector  1502  that has a jack  1508 . The fluid detection cable has a connector  1506  that may be plugged into the jack  1508  of the detector  1502 . A leak near the water heater can be detected using the fluid detection cable and a detector. The cable may form a loop surrounding an area to be monitor so that, when the perimeter of the fluid extends to the loop of cable, it is detected. This configuration allows immediate detection of a water heater leak before major damage occurs. The fluid detection system may also be connected so as to turn off valve(s) automatically which would be well suited for applications where a building is left unoccupied for periods of time. 
     FIG. 16  illustrates the use of a fluid detection cable  1612  in an application near a dishwasher  1600 . The fluid detection cable  1612  has a connector  1610  that may be plugged into a coupler  1608 . The porous polymer jacket surrounding the sensing leads of the fluid detection cable  1612  prevents false fluid detections from contact with the metal edges of the dishwasher. A leader cable  1604  may have a first end with a connector  1606  that may be plugged into the coupler  1608 . A second opposite end of the leader cable  1604  may be connected to a monitor  1602 . The flexibility and flatness of the fluid detection cable  1612  and the leader cable  1604  make them easy to install in this type of application. Leader cables and corresponding jacks may be pre-installed inside walls prior to hookup of appliances, thus facilitating installation of fluid detection cables at the time appliances are installed. 
     FIG. 17  illustrates the use of a first fluid detection cable  1710  that is adjacent and beneath a water pipe  1714 . A second fluid detection cable  1722  may be adjacent to the bottom flow plate of a wall and near to the basement floor  1716 . A detector/transmitter  1708  may be connected to the first fluid detection cable  1710  and to a second fluid detection cable  1722 . The detector/transmitter may have antenna  1706  that is connected to a remote first monitor  1700  and antenna  1702  via a wireless connection  1704 . The detector/transmitter may transmit through house wiring  1718  to a second monitor  1720 . Small leaks may thus be detected because the water will flow to the under side of the pipe and contact the fluid detection cable. Such configurations allow detection of leaks inside walls or at other remote locations. Larger leaks can be detected more quickly using this arrangement of the fluid detection cable and an alarm can be sounded so that actions such as shutting a supply valve can be taken to minimize damage. Electronically controlled valve(s) may be connected to the monitor so that when a leak is detected the monitor causes the valve(s) to shut or close. 
     FIG. 18  illustrates the use of a fluid detection cable  1802  in an application near a drainpipe. The fluid detection cable is connected to a monitor  1800  and may be disposed on the upper surface of a flow plate  1804 . The fluid detection cable may pass through a hole  1808  in a stud  1806  and then again be disposed on the upper surface of the flow plate  1804  that is below the drainpipe  1810 , thus allowing the detection of leaks from a drain pipe inside a wall or at other remote locations. The fluid detection cable  1802  may form a perimeter around a floor drain  1812  as depicted in  FIG. 18  such that if the floor drain  1812  is blocked and water backs up, the water will contact the fluid detection cable  1802  and the fluid can be detected. 
     FIG. 19  illustrates the use of a fluid detection cable  1904  in an application where the cable is installed beneath a carpet  1902 . The fluid detection cable may have a connector  1906 . The connector  1906  may plug into a coupler  1908 . A monitor  1900  may be connected to a leader cable  1912  that has a connector  1910  at the end farthest from the monitor. The connector  1910  may plug into the coupler  1908  and provide an electrical connection from the monitor  1900  to the fluid detection cable  1904  through connector  1906 . The use of inexpensive connectors combined with the flat fluid detection cable  1904  facilitates the installation and removal of the cable beneath the carpet  1902  and eliminates bumps in the carpet  1902 . Leader cables, such as leader cable  1912 , may be pre-installed for more convenient construction and installation. 
     FIG. 20  illustrates the manner in which a loop  2000  can be formed with the fluid detection cable. Existing fluid detection cables are not constructed in a manner that allows a tight turning radius. The tight turning radius and flat ribbon construction of the various embodiments of fluid detection cables disclosed herein permits the formation of a loop. The flatness or small diameter of the fluid detection cable and the tight turning radius allow the lengths of the cable extending from the loop to be placed substantially flat on a surface thus minimizing any gap between the cable and the surface that is being monitored for fluids. A larger loop may also be made that provides a spare length of cable that may be utilized if it is necessary to cut off a connector from the cable for removal or repair. 
     FIG. 21  illustrates a bend radius  2100 . The construction, flatness and size of the various embodiments of fluid detection cables allow these cables to be installed in applications that require a tight turning radius. 
     FIG. 22  illustrates one embodiment of a holder  2200  that may be used to install the various embodiments of the fluid detection cable disclosed herein. A hole is formed in holder  2200  that may be used with a nail, screw, bolt or other fastening device to fasten the cable to a surface. 
     FIG. 23  illustrates another embodiment of a holder  2300  that may be used to install the various embodiments of the fluid detection cable disclosed herein. The holder  2300  has an adhesive back  2302  that may be used to hold the cable to a surface in applications where it is undesirable to penetrate the surface with a fastening device. 
   Hence, the various embodiments of the fluid detection cable disclosed provide a cable with numerous advantages. The non-conductive polymer shielding that at least partially surrounds the conductive polymers and/or conductors provides a fluid detection cable that does not short circuit when in contact with non-liquid conductive surfaces and at the same time permits fluids to make electrical contact with the sensing leads. The conductive polymer jacket surrounding the conductors in various embodiments of the fluid detection cable protects the conductors from corrosion due to contact with corrosive fluids. The size and flatness of the various embodiments of the fluid detection cable make it easy to install and remove, especially in applications that require the fluid detection cable to be installed in tight places, locations requiring tight bends in the cable, and/or beneath carpet or other floor coverings. The size and shape of the various embodiments of the fluid detection cable disclosed is such that low cost industry standard connectors, jacks, tools and accessories may be used to connect, install and use the various embodiments of the fluid detection cable providing a significant advantage in residential or other applications that require low cost. Various embodiments of the fluid detection cable may comprise materials that facilitate the use of resistive measurement fluid detection systems or TDR systems to determine the location of the fluid. 
   The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.