Abstract:
A leak detector apparatus and system for use with a drop ceiling having a grid-work of ceiling tiles. The leak detector apparatus includes an electrically non-conducting tile body that is shaped and dimensioned to rest on top of a ceiling tile. The tile body comprises multiple layers of non-conducting closed cell-foam and has a plurality of water collector cups formed or positioned therein. Spaced-apart sensor wires are provided and form an electrical grid that extends between the multiple layers of the tile body and the sensor wires generally extend through the water collector cups. The sensor wires are operative to sense the presence of water in the cups. An electronics module is provided at each tile body and is associated with the sensor wires and electrically coupled to the sensor wires for triggering an alert in response to the presence of water in one or more of the cups. A master controller is in communication with the local processors for monitoring the function and operation of each local processor. Thus, each leak detector tile has its own electronics module associated with it, thereby providing excellent location precision when installed in the room.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The benefit of the filing date of U.S. provisional patent application Ser. No. 60/700,761, filed Jul. 20, 2005, entitled WATER DETECTION CELL AND SYSTEM, is hereby claimed, and the specification thereof is incorporated herein by this reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to a water sensing system and in particular relates to a water detection system for use with drop ceilings. 
     BACKGROUND OF THE INVENTION 
     Every year, considerable damage is done to homes and business establishments by leaking water from roof leaks, plumbing fixtures, pipes, water heaters, air conditioners, and other appliances. These leaks often occur for a long period of time before any evidence or damage is noticed, often with catastrophic results, such as floors falling in or ceiling material dropping into the room below. This damage often results in insurance claims and settlements that cost businesses, consumers and insurance companies untold millions of dollars per year. Although there are some leak detection systems in the market, most are expensive, complicated, and/or difficult for the user to install. 
     In recent years the so-called dropped ceiling has become popular. In this arrangement, a grid-work of thin metal beams is suspended from the ceiling or other structure. Ceiling tiles are then placed in the (rectangular or square) openings defined by the grid-work. This ceiling is popular in homes and offices alike. 
     In many instances, the drop ceiling is positioned above a room containing expensive or critical equipment or inventory. A ready example of this is the ubiquity of computers and computer servers in modern offices, typically below a drop ceiling. When there would be a water leak above the drop ceiling, the drop ceiling tends to obscure the leak until it becomes a substantial problem. It often occurs that the leak develops at night, on weekends, or other times when workers might not notice immediately. These leaks can be catastrophic to the operation of a business. For example, consider a web-based business that relies heavily on its computers and servers. A flood in a room housing such equipment poses a serious risk to the enterprise. 
     One approach to this problem has been a leak detection system provided by Dorlen Products Inc. of Milwaukee, Wis., under the trademark CEILING GUARD. This product comprises a series of sensing panels affixed to a customer&#39;s ceiling. Each panel is in the form of a trough with liquid sensors positioned in the bottom of the trough. The troughs are electrically connected to one another in order to be able to monitor a large zone. Each zone, which can be up to 320 ft. 2 , terminates in a detector module that provides audible alarms for water sensed in the zone and signals a central monitoring controller or panel that there has been a problem. These sensing panels are provided with end ribs or dams that prevent liquid from leaking out of the sensing panels. However, retaining all of the moisture in these troughs can lead to a catastrophic failure of the ceiling inasmuch as a typical drop ceiling is not intended to support the weight of a substantial amount of water. Moreover, these sensing panels can be difficult for an end user to install. Furthermore, this zone approach does not inform the user about which panel has suffered a liquid leak, but instead only informs the user of which zone is suffering from a liquid leak. 
     Accordingly, it can be seen that a need yet remains in the art for a leak detection system and leak detector tile that is easily installed, is relatively inexpensive, provides precise leak location sensing, and is reliable in operation. It is to the provision of such a leak detection system and leak detector tiles that the present invention is primarily directed. 
     SUMMARY OF THE INVENTION 
     Briefly described, in a first preferred form the present invention comprises a leak detector apparatus for use with a drop ceiling having a grid-work of ceiling tiles. Preferably, the leak detector apparatus includes an electrically non-conducting tile body that is shaped and dimensioned to rest on top of a ceiling tile. The tile body comprises multiple layers and has a plurality of water collector cups formed or positioned therein. Spaced-apart sensor wires are provided and form an electrical grid that extends between the multiple layers of the tile body and the sensor wires generally extend through the water collector cups. The sensor wires are operative to sense the presence of water in the cups. An electronics module is associated with the sensor wires and is electrically coupled to the sensor wires for triggering an alert in response to the presence of water in one or more of the cups. Thus, each leak detector apparatus or leak detector tile has its own electronics module associated with it, thereby providing excellent location precision when installed in the room. In this way, leaks can be pinpointed, as opposed to simply being indicated as being somewhere in a large zone. 
     Preferably, the tile body is formed in such a way as to have shallow funnels for collecting water and funneling the water into the collector cups. Advantageously, the tile body is formed from a flexible, closed cell, non-conducting foam, allowing it to be configured or conformed to varying shapes as required. This can be very handy when working around obstructions and corners, etc. 
     Preferably, the spaced-apart sensor wires are spaced from one another horizontally and vertically. Optionally, these spaced-apart sensor wires can be spaced apart only horizontally or only vertically. Preferably, the sensor wires can be positioned between adjacent layers of the foam tile body. Advantageously, the foam acts to insulate the wires such that otherwise bare wire can be used in the leak detector tile. 
     Optionally, the tile body has dimples formed in a lowermost layer thereof, which tends to deepen the water collector cups. This feature can be used to create or combined with the form of the lowermost layer to support the tile body substantially above the ceiling tile to minimize the growth of mold, algae, mildew, and/or fungus on the underside of the tile body. 
     Optionally, the spaced apart sensor wires form a grid in the tile body in such manner as to allow the tile body to be trimmed to a final dimension, as in being trimmed to a final length or final width and/or both. This allows for greater flexibility in installing the leak detector in many applications. 
     In another form of the invention, the present invention comprises a leak detection system for use with a drop ceiling of the type having a plurality of ceiling tiles and grid frames supporting the ceiling tiles. The leak detection system includes a plurality of lightweight leak detection tiles. The leak detection tiles are adapted to be placed on top of the ceiling tiles of the drop ceiling. Each of the leak detection tiles includes one or more sensors for detecting the presence of liquid at one or more locations on the ceiling tile. Local processors (electronic modules) are provided and are electrically coupled to the sensors, with the local processors being provided one per leak detection tile. A master controller is provided in communication with the local processors for monitoring the function in operation of each local processor. 
     In this way, master controller can determine which, if any, of the leak detection tiles has detected a leak. This also allows the local processors to be linked to one another in a simplified, daisy-chain arrangement. 
     Optionally, the leak detection system can include deflector roofs that are adapted to be positioned atop the grid frame for deflecting liquid that might otherwise impinge on the grid frame and for deflecting that liquid onto an adjacent leak detection tile. Optionally, the deflector roofs can be made from flexible foam to allow them to be cut to length and conformed to fit closely against the grid and/or wires supporting the grid. 
     Other features and advantages of the invention will become evident from reading the following description of the invention in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a leak detector unit having a plurality of layers according to a first example embodiment of the present invention. 
         FIG. 2  is a perspective view of an internal layer of the leak detector unit shown in  FIG. 1 . 
         FIG. 3  is an exploded perspective view of the leak detector unit shown in  FIG. 1 . 
         FIG. 4  is a perspective view of the leak detector unit shown in  FIG. 1 . 
         FIG. 5  is a cutaway perspective view of the leak detector unit shown in  FIG. 1  depicted with a deep cup. 
         FIG. 6  is a cutaway perspective view of the leak detector unit shown in  FIG. 1  depicted with a shallow cup. 
         FIG. 7  is a perspective view of a plurality of leak units shown in  FIG. 1  arranged into a leak detector apparatus. 
         FIG. 8  is a cutaway view of a leak detector apparatus as shown in  FIG. 7 . 
         FIG. 9  is a perspective view of a plurality of leak detector units shown in  FIG. 1  arranged into a roll of leak detector apparatuses. 
         FIG. 10  is a plan view of a wiring diagram for the leak detector apparatus shown in  FIG. 7 . 
         FIG. 11  is a plan view of a leak detection system according to a second example embodiment of the present invention. 
         FIG. 12  is a software process diagram for the leak detection system shown in  FIG. 11 . 
         FIG. 13  is a software process diagram for the leak detection system shown in  FIG. 11 . 
         FIG. 14  is a plan view of a wiring diagram for a portion of the leak detector apparatus shown in  FIG. 11 . 
         FIG. 15  is a functional diagram for the leak detection system shown in  FIG. 11 . 
         FIG. 16  is a perspective view of a master controller portion of the leak detection system shown in  FIG. 11 . 
         FIG. 17  is a functional diagram of the construction and operation of the master controller of  FIG. 16 . 
         FIG. 18A  is a perspective view of a leak detector unit having a plurality of layers according to another example embodiment of the present invention. 
         FIG. 18B  is a sectional view of a leak detector unit according to  FIG. 18A , taken along lines A-A. 
         FIG. 19  is a perspective view of a leak detector unit according to another example embodiment of the present invention and shown including an interrupted peripheral rim. 
         FIG. 20  is a perspective view of a leak detector unit according to another example embodiment of the present invention and shown including a roof deflector for deflecting falling liquid away from the support grid that supports a drop ceiling. 
         FIG. 21A  is a perspective view of a leak detector unit according to another example embodiment of the present invention and shown from the underside of a drop ceiling and including an alarm indicator lamp for visually indicating which ceiling tile in a drop ceiling has or is suffering a leak. 
         FIG. 21B  is a perspective, detailed view of an alarm indicator lamp portion of the leak detector unit of  FIG. 21B . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may be understood more readily by reference to the following detailed description of the invention taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention. Also, as used in the specification including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. 
     With reference now to the drawing figures, in which like numerals represent like elements or steps throughout the several views,  FIG. 1  depicts a leak detector unit  1  according to a first example embodiment of the present invention. The leak detector unit  1  is preferably constructed of three or more layers of foam, rubber, and/or plastic, however, other appropriate non-conducting, non-absorbing materials can be used. In example embodiments, the leak detector unit has a body comprised of a top layer  9 , a middle layer  4 , and a bottom layer  7 . Preferably, the layers have appropriate adhesive coatings on each to allow them to be permanently bonded together. In  FIG. 1  the leak detector unit  1  is shown in a square configuration with sides approximately 4 inches long, but it should be noted that the leak detector unit can be constructed in virtually any size or shape. 
     In example embodiments, the leak detector unit  1  includes a waterproof, or otherwise water resistant, water diversion surface  2  and a water collection cup  3 . The water diversion surface  2  funnels any water that contacts the surface towards a water collection cup  3 . The water collection cup  3  is preferably positioned in the center of the leak detector unit  1  in order to receive any such water. The leak detector unit  1  also includes a water dam or lip  8  that lines the circumference of the unit&#39;s top layer  9 . The water dam  8  helps direct water that may reach the diversion surface  2  towards the collection cup  3  rather than escape. The water collection cup  3  is formed by creating an opening in some, but not all, of the layers of the leak detector unit&#39;s  1  body. The opening is depicted in the shape or a circle; however, the opening can be any desired shape. 
     The leak detector unit  1  also includes a water sensing mechanism as seen in  FIG. 1 . In example embodiments, the water sensing mechanism is formed by two wires: a top sensor wire  5  and a bottom sensor wire  6 . The wires are placed within the water collection cup  3 . It is preferable, but not required, that each wire is non-insulated and coated with conduction materials that resist corrosion and oxidation for the life of the cell. Water (not shown) that bridges top sensor wire  5  and bottom sensor wire  6  creates an electrical contact, wherein the electrical resistance between the top sensor wire  5  and the bottom sensor wire  6  is lowered significantly. By lowering the electrical resistance between the two wires a sensor attached to the wires can detect the presence of water in the unit  1  (discussed further below). 
     Referring now to example embodiments depicted in  FIG. 2 , top sensor wire  5  can be placed on the top surface of middle layer  4  so that it rests between the middle layer  4  and the top layer  9 . Adhesive  10  can be used to help secure the wire  5  to middle layer  4 . Though shown in a single unit configuration in  FIG. 2  the wire can continue to other water collection cups  3  to form a leak detector apparatus, which will be discussed in greater detail below. The bottom sensor wire  6  can be similarly placed on the bottom of the middle layer  4 , and can be further secured in place with an adhesive  11 . Thus, in example embodiments, the top sensor wire  5  and the bottom sensor wire  6  can be physically separated from each other by the thickness of middle layer  4 . By configuring the leak detector unit  1  in this fashion, the unit can be adjusted for water sensitivity during the manufacturing process. 
       FIG. 3  shows the leak detector unit  1  before assembly. As previously discussed, the middle layer  4 , along with top sensor wire  5  and bottom sensor wire  6 , is placed between the top layer  9  and bottom layer  7 . The water collection cup  3  is created by a collection cutout  12 , along the top layer  9 , and by water collection cup middle  3   a  and water collection cup bottom  3   b . The layers are then pressed together, and secured by the top adhesive surface  10  and the bottom adhesive surface  11 . Adhesive layers can also be added to the bottom of the top layer  9  and the top of the bottom layer  7  to strengthen the bond if necessary.  FIG. 4  shows the completed assembly after being pressed together and the bonding of the appropriate surfaces. 
     The water collection cup  3  and sensor wires  5 ,  6  form a water sensor system. As it is best seen in  FIG. 5 , the water collection cup  3  is formed by the bonding of the layers together as previously discussed. The adhesives applied to the layers&#39; surfaces bond the layers, and form a seal to prevent collected water from escaping the water collection cup  3 . The bottom of the water collection cup  3  is formed by an indention in the bottom layer  7 . The depth of the water collection cup  3  can be formed by the depth of the indention  15  and the thickness of middle layer  4 . It is preferred that the bottom sensor wire  6  does not remain in contact with any dampness in the bottom of the water collection cup  3  because of the indention  15 , thereby minimizing any corrosive effects of long term moisture. Thus the sensitivity of the sensor can be adjustable in the manufacturing process by adjusting the thickness of the middle layer  4 , the depth of the indention  15  in the bottom layer  7 , and the area of the opening forming the water collection cup  3  (in this case the diameter). 
     Example configurations of the water collection cup  3  and the sensor wires  5 , 6  are designed to minimize false alarms from condensation or other sources of minute amounts of water that do not pose a threat to equipment or safety. This is accomplished by three features:
         1. The depth of the water collection cup  3  requires a specific amount of water to be present before both sensor wires  5 , 6  are immersed in the water. The amount of water required is proportional to the diameter and depth of the water collection cup  3 .   2. The sensor wires  5 , 6  are physically separated in the vertical and horizontal planes. Water droplets cannot lodge between the sensor wires because of the small surface areas and gravity.   3. The surface area of the sensor wires  5 , 6  that comes in contact with the foam is very small. Thus, condensation that tends to coat all surfaces produces an extremely small conduction path.       

       FIG. 6  depicts a leak detector unit  1  configured with a thinner bottom layer  7  than shown in the previous examples. In this regard, a much smaller amount of water is needed before the water bridges the sensor wires, resulting in a more sensitive leak detector unit. Various other means of adjusting the leak detector unit  1  are capable of being used including, adjusting the height of the sensor wires within the cup  3 , adjusting the thickness of the middle layer  4 , etc. 
     While the aforementioned description of the leak detector unit  1  is only one individual unit, in actual practice, the cells can be combined into virtually any shape and/or configuration to create a leak detector apparatus  13 . One such configuration, for example, is shown in  FIG. 7 . This example configuration uses multiple units to produce a large, two feet by two feet ceiling tile mat. In other example embodiments, the tile mat can be other standard sizes including 4 feet by 2 feet. The ceiling tile mat depicted in  FIG. 7  can cover about 4 square feet and can potentially sense the presence of water anywhere within that area. 
     In example embodiments, the sensing wires  5 , 6  are continuous, as shown in  FIG. 8 , and can be placed within all of the water collection cups  3  during the manufacturing process, making the leak detector apparatus very easy and inexpensive to produce. Each layer of the leak detector apparatus can be die-cut or molded to the required configuration on a full sized basis. For example, each layer of the apparatus  13  can be formed in one full size sheet, instead of unit-sized pieces. If the apparatus  13  needs to be trimmed to fit a desired installation, the apparatus can be cut along lines  25  as seen in  FIG. 8 . Of course, there are numerous configurations for wiring the apparatus  13 , and therefore numerous ways that the apparatus can be trimmed to fit a particular installation. It should also be noted, that the apparatus  13  is flexible and can be folded if desired by a user. 
     In other example embodiments, the leak detector units  1  can be configured in a long roll mat  14  as seen in  FIG. 9 . In still other embodiments, the units  1  can be constructed in even longer rolls, such as carpet sized rolls, for water sensing abilities over large areas. 
       FIG. 10  depicts an example leak detector system  90  to be used in conjunction with the leak detector apparatus  13 . In preferred embodiments, a microprocessor  32  is mounted onto a printed circuit board  30 . The microprocessor  32  interfaces with the top sensor wire  5  and the bottom sensor wire  6  via electronics  31  to determine if water has bridged the top sensor wire and the bottom sensor wire. If the microprocessor  32  determines that water is present, the microprocessor will activate the local indicator  36 , which may be a light, audible sound, etc., to alert the user of the presence of water. In other preferred embodiments, the microprocessor  32  will notify a user of the location water was detected. The microprocessor  32  also interfaces with a master controller  100  ( FIG. 11 ) via general circuitry, connectors  35 ,  36  and cable  33 . In example embodiments, the microprocessor  32  responds to the master controller  100  as a slave unit using a polling scheme. In other words, the status of the microprocessor  32  is transferred to the master controller only when the master controller polls the microprocessor at a unique specific address. Connectors  37  and  38  forward the polling information, via cable  39 , to any sequential leak detector systems  90  to allow the master controller  100  to poll all systems present. 
     Example embodiments of the full system configuration  200  are best seen in  FIG. 11 . In operation, the master controller  100 , which is typically a microprocessor using a polling scheme, polls the leak detector system  90 , shown as  90 A,  90 B, and  90 C (each having a circuit board  30 A,  30 B,  30 C). Although only three leak detector systems are shown in  FIG. 11 , the number of systems used in a particular application can vary from one to as many systems that are needed. The master controller  100  is connected to the leak detector systems  90  by several wires consisting of the transmitter signal wire  112 , the receiving signal wire  113 , the power voltage wire  106 , and the system ground wire  105 . While this configuration details a four-wire system, more or less wires can be used to achieve the same result. In preferred embodiments, all leak detector systems  90  are powered by the master controller  100 , wherein the master controller is powered by a standard international AC transformer system. The master controller  100  can also contain a battery back up to provide service when the power is out. 
     As previously mentioned, the full system configuration  200  operation uses a continuous polling technique to verify that the leak detector systems  90  are responding and therefore operational. Additionally, the full system configuration  200  interrogates the status of each leak detector system  90  in turn. When water is sensed at any of the leak detector systems  90  within the full system configuration, the master controller  100  will receive the status and can alert the user via the master controller interface  114 . The master controller interface  114  can be a multitude of interfaces depending upon the application, but in preferred example embodiments, the interface can be a contact closure, an alarm sounder, an LED indicator, an appropriate interface to a computer, an auto dialer interface, or any other means of interface to standard devices as required. 
       FIG. 12  shows an example software overview flow chart for the master controller software  400 . Step  401  is the entry point into the software code stored within non-volatile memory in the master controller  100  ( FIG. 11 ). Step  402  is the start up code that initializes all internal registers, input registers, and output registers, conducts a self-diagnostic test, and jumps to the application program. Step  403  is a decision block that decides if the master controller  100  is functioning properly. If it is not, the program jumps to step  408  to issue an alert to the user that something is not working properly and then moves to step  402  to continue checking for errors. If it is functioning properly, the program jumps to step  404 . Step  404  is the polling code that polls all of the leak detector systems  90  attached to the master controller  100 . It is a serial protocol that contains a sequential address for all leak detector systems  90  to read, and then the master controller  100  waits for a reply from the addressed leak detector system. The address is sequenced until all attached leak detector systems  90  have been polled. Step  405  checks to see if the leak detector system  90  responded. If it did not, the program jumps to step  409  which alerts the user that a leak detector system  90  is not responding and then moves to step  404  to continue polling. If it did receive a response, the program jumps to step  406 . Step  406  parses the information flags sent from the leak detector system  90  to check to see if water is present in the leak detector system&#39;s  90  individual units  1 . If water is detected, the program jumps to step  410 , which issues a master alert as previously described above and jumps to step  407  to increment the address and then jumps to step  404  to continue polling. If water is not detected in step  406 , the program jumps to step  407  and increments the address to be sent to the leak detector systems  90  until all systems have been interrogated. The program then loops back to step  404  and continuously loops through the steps as described above. 
       FIG. 13  shows another example software overview flow chart for the leak detector system  90  software  500 . Step  501  is the entry point into the software code stored within non-volatile memory in the microprocessor  32  (shown in  FIG. 10 ). Step  502  is the start up code that initializes all internal registers, input registers, and output registers, conducts a self diagnostic test, and jumps to the application program. Step  503  is a decision block that decides if the microprocessor  32  and associated circuitry is functioning properly. If it is not, the program jumps to step  508  to set an error flag to alert the master controller  100  that something is not working properly and then moves to step  509  to continue. If it is functioning properly, the program jumps to step  509 . Step  509  is a decision block that checks to see if the master controller  100  is polling the leak detector system  90 . If polling is not occurring, the program jumps to step  510  to check for the presence of water. If polling is occurring, the program jumps to step  504  to check for an address match from the master controller  100 . If the address does not match the slave address, the program ignores the polling information and loops back to step  509  to continue monitoring. If the address matches in step  504 , then the addressed leak detector system  90  sends all flags to the master controller  100 , in step  505 , and then loops back to step  509  to continue monitoring. In step  510 , if water is not detected, the program jumps to step  511 , which resets the water detected flag and then loops back to step  509  to continue monitoring. If water is detected in step  510 , the program jumps to step  506  to set the water detected flag. Subsequently the program then jumps to step  507  to activate the local alert indicator and then loops back to step  509  to continue monitoring. 
       FIG. 14  is a plan view of a wiring diagram for a portion of the leak detector apparatus shown in  FIG. 11 . The circuit  550  shown in this figure is designed to minimize supply current and to provide reliable sensing of the water when present. The wires  555  and  556  are connected to the input via jack J 4   559  as shown above. Zener 1   554  is a zener diode that serves as a static discharge arrestor across the sensor to prevent damage to the high impedance circuitry. FET transistor Q 1   551  provides the switching function required to sense the presence of the water. It has a very high input impedance using resistors  552  and  553  and the ability to sense micro currents on its gate  558 , resulting is in a digital switching function at the T out node  557 . 
       FIG. 15  is a functional diagram for the leak detector system shown in  FIG. 11 . As shown herein, the master controller  100  can receive an indication from any of one or more of the leak detector tiles and can then take action in response thereto. These actions can include using an auto dialer to initiate a page call or a voice call, using the alarm system to communicate with an external alarm system, and/or using simple network management protocol (SNMP) to sound a network alarm. 
       FIG. 16  is a perspective view of a master controller  100  of the leak detection system shown in  FIG. 11 . Of course, it will be understood that the master controller depicted in this figure is for illustration purposes only and that the master controller can take various forms or shapes.  FIG. 17  is a functional diagram of the construction and operation of the master controller of  FIG. 16 . Some features and functionality that one skilled in the art might wish to provide in the master controller  100  include the following:
         1. An LCD display to show all system information and status. It will be a monochrome backlit graphic display that will display text and graphics as need to make the controller user friendly and unambiguous.   2. Power on/off switch—preferably, an embedded slide switch that will not be easily bumped   3. An LED display showing AC power is present   4. A Battery Warning Light that flashes if the battery is becoming discharged   5. A Sonalert audio warning device to provide audio feedback of issues   6. Control Switches that control the action of the master controller
           a. Lights on when polling   b. Light off when polling   c. Remote alerts off   d. Remote alerts on   e. Diagnostic poll of all tiles   
           7. Power input jacks   8. Optional USB interface—this could ultimately allow a computer to operate and manage all of the functions of the master controller.   9. Optional Auto-dialer to dial phone numbers and present a prerecorded audio message when the alarm is present.       

       FIG. 18A  is a perspective view of a leak detector unit having a plurality of layers according to another example embodiment of the present invention. In this embodiment, the leak detection cell, which is contemplated to be just one of many that is used in a leak detector tile, is made from these two layers of closed cell foam, rather than three layers of closed cell foam as depicted in  FIG. 1 . Indeed, the leak detector tile is contemplated according to this embodiment to be made up of two layers of closed cell foam. The leak detector unit  600  includes an upper layer  601  and a lower layer  602 . In this embodiment, the wires  605  and  606  lie the same horizontal plane and are not separated by a layer foam positioned therebetween. This construction has the advantage over that shown in the first embodiment of being simpler to construct and cheaper. Like in the first embodiment, the leak detector unit  600  has a funnel shape formed in the top of upper layers  601  to help funnel water into the collector cup for sensing by the wires  605  and  606 . While  FIG. 18A  depicts a pyramidal funnel shape, those skilled in the art will recognize that any funnel shape can be provided, such as a flat cone. 
       FIG. 18B  is a sectional view of a leak detector unit according to  FIG. 18A , taken along lines A-A. As best seen in this figure, the water collection cup  603  is formed by creating an opening in the upper layer  601  and a depression in the lower layer  602 . This depression in the lower layer  602  creates a foot  611  that tends to deepen the water collector cup  603  and also acts to stand the leak detector unit above the upper surface of a ceiling tile upon which it rests. This tends to minimize the growth of algae, fungus, mildew, etc. underneath the leak detector tile. 
       FIG. 19  is a perspective view of a leak detector unit  700  according to another example embodiment of the present invention and shown including an interrupted peripheral rim  701 . With this construction, water cannot build up to dangerous levels leading to a catastrophic failure of the ceiling. Instead, if the leak continues unabated, as water collects in the collector cups and then floods the top of the collector tile  700 , water can escape in the corners thereof, such as corner  702 . The peripheral rim  701  is interrupted in the four corners, providing the water with an escape. In this way, excessive water weight is prevented from being borne by the ceiling tile. 
       FIG. 20  is a perspective view of a leak detector unit  800  according to another example embodiment of the present invention and shown including a roof deflector  801  for deflecting falling liquid away from the support grid that supports a drop ceiling. The roof deflector  801  preferably is made from closed cell foam and is easily trimmed to length to cover the grid of support beams (such as support beam  803 ) holding up the ceiling tiles and the leak detection tiles. The roof deflector preferably is extruded to include a central slot on the underside thereof to allow it to be snugly fitted to the upstanding web  804  of the support beam. This tends to secure it in place and makes installation easy. 
       FIG. 21A  is a perspective view of a leak detector unit according to another example embodiment of the present invention and shown from the underside of a drop ceiling  902  and including an alarm indicator lamp  901  for visually indicating which ceiling tile in a drop ceiling has or is suffering a leak. 
       FIG. 21B  is a perspective, detailed view of the alarm indicator lamp  901  of the leak detector unit of  FIG. 21A . As can be seen in this and the preceding figure, the alarm indicator lamp  901  wraps around the edge of the ceiling tile along the edge of the support beam  903  holding up the ceiling tile. 
     Advantageously, the inventions described herein can be scaled up easily to produce larger sensor systems (it is scalable). The leak detector of the present inventions can be manufactured in many sizes, shapes, and materials. Moreover, the design of the present inventions allows the sensitivity to be adjusted (the amount of water required to sense) in the manufacturing process. It is also simple, reliable, and can be installed easily by an end user. By using foam to form the leak detection tiles, they are flexible and can be folded or bent to conform to smaller areas. It also can be trimmed or folded to fit smaller areas without altering its functionality. 
     Advantageously, the design of the present invention allows for a low false alarm rate and is not unduly sensitive to minute quantities of water that pose no significant threat or danger. 
     Notably, devices according to the present invention can detect the presence of water and alert the end user, and can also indicate more specifically where the water was detected by sending the location to the master controller and/or using an alert means local to each sensing entity. 
     The invention can be manufactured in large coverage configurations that are easily installed by the end user. Moreover, the invention provides a low cost per square foot solution and is made from readily available materials. It does not absorb water and is reusable when the water is no longer present. Further, the size, width, length and shape of the leak detector tile can be varied without negatively impacting its effectiveness as a liquid sensor. 
     While the invention has been described with reference to preferred and example embodiments, it will be understood by those skilled in the art that a variety of modifications, additions and deletions are within the scope of the invention, as defined by the following claims.