Abstract:
A wireless electronic monitor for a container such as an aquarium is described. The apparatus comprises a sense and transmit assembly (STA)  15  configured with a pH sensor  6  submerged in the water inside the aquarium, and a receive and display assembly (RDA)  33  that displays the output of the sensor  6 . A line-of-sight orientation is maintained between openings in each assembly using magnets to generate a clamping force on a transparent tank wall  16 . A water test button  22  is pressed, and a single pulse of light travels from the RDA  33  to the STA  15 . The single pulse of light turns the STA  15  on by closing a timed switch to the battery power. The pH sensor  6  output is converted to a train of frequency-modulated pulses of light that are transmitted back to the RDA  33 . The frequency of the train of light pulses is determined by a CPU in the RDA  33 , and assigned a pH value from calibration tables stored in electronic memory. The pH value is shown on a pH sensor output display  20  which can be manually placed anywhere on the tank wall by grasping the RDA  33  from the outside of the aquarium, and sliding the entire monitor to its desired location without getting wet hands. To fully realize a true monitor of the pH, the CPU in the RDA  33  is programmed to make periodic measurements of the pH by periodically emitting the single pulse of light to the STA  15 . The results of each measurement are compared with upper and lower pH boundaries stored in an electronic memory. If a measurement is outside of a pre-determined range, the CPU activates an alarm speaker  28  and an alarm light  30.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable 
       FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable 
       SEQUENCE LISTING OR PROGRAM 
       [0003]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of Invention 
         [0005]    This invention relates to electronic sensing and monitoring devices, specifically a wireless electronic monitor of pH and the like for aquariums. 
         [0006]    2. Prior Art 
         [0007]    Previously, a pH measurement of water in a container such as an aquarium was done using colorimetry, a process wherein the color of an indicator chemical mixed with the water under test is compared with a chart that approximately correlates that color with a discrete value of pH. Colorimetry by its nature does not provide an output as a sensor that can be processed by electronic circuitry, and is therefore not a suitable sensor for a monitor that provides a warning when pH levels are outside of a desired range. 
         [0008]    A combination electrode of the type available from Omega Engineering of Stamford, Conn. generates a voltage dependent on ionic activity in the water, can be configured to measure pH, and can operate continuously immersed in the water being tested. The combination electrode requires a meter to be useful, and a basic meter configuration includes a display of the pH or other ionic activity and some method to calibrate the electrode with standard solutions. 
         [0009]    While the use of the combination electrode is ubiquitous in science and industry, it is not common in aquarium keeping and the like. Most typical pH measurement systems available from scientific instrument suppliers have a cable or wire and have a meter that either sets upon a benchtop or is mounted in an equipment panel. A notable exception is a handheld pH tester with the electrode and the display integrated into a compact and rugged field instrument. For a container such as a tank, the combination electrode typically penetrates the wall of the tank using a bulkhead fitting or similar to make a watertight connection. The combination electrode is not always connected directly to a meter with a coaxial cable. A transducer that converts the electrode output to a modulated current source is well known as a transmitter. Additionally, the combination electrode output can be sent through ambient air using radio waves or infrared light to a remote meter using prior art. Lastly, industrial process control applications commonly use a set-point monitor to provide a warning or alarm when the pH of a process is not within specified limits. 
         [0010]    A limitation of using a typical electrode and meter is the coaxial cable or wire connecting the two. 
         [0011]    A limitation of the typical meter and combination electrode is that there is no convenient surface to place it near a typical aquarium, or to mount the electrode. The typical scientific or industrial pH measurement equipment is not an aesthetically pleasing addition to the natural environment that an aquarium attempts to represent. 
         [0012]    A limitation of a handheld pH test meter is that the typical design is intended for sampling applications, and has neither an intrinsic means of attachment to a tank or a set-point alarm that would make it a true monitor. 
         [0013]    A limitation of measuring the pH of a liquid in a tank or container in most industrial applications is the requirement to penetrate the wall so that the combination electrode has access to the interior of the tank. 
         [0014]    A limitation of using radio waves to transmit the output of the electrode to a meter is that the antenna attached to the transmitter must be kept above the surface of the liquid within the tank if the liquid is conductive, such as saltwater. This is due to the phenomena of attenuation of an electromagnetic field in a conductive fluid. 
         [0015]    A limitation of the typical pH measurement system configured with a set-point monitor is again the industrial nature of the typical equipment available. A pH electrode would either have to penetrate the wall of the aquarium, or would have to be mounted to the lip around the edge, similar to how many aquarium heaters are attached. It is preferable to keep the electrode and the meter below the lip of the aquarium to avoid interference with the cover of the tank. 
       OBJECTS AND ADVANTAGES 
       [0016]    Accordingly, several objects and advantages of the present invention are:
       1. to provide an automatic and periodic measurement of pH in a container such as an aquarium not possible with colorimetry;   2. to eliminate the use of a coaxial cable or wires between the pH sensor and the pH display;   3. to provide a small device that can be conveniently placed anywhere on any wall of an aquarium;   4. to eliminate the need to penetrate the wall of an aquarium or similar container;   5. to provide an efficient wireless transmittal of sensor output from within a salt water aquarium that cannot be blocked by objects within the aquarium;   6. to provide an alarm when the pH of an aquarium is outside of pre-determined limits; and   7. to obviate the need to personally test the water of an aquarium regularly.       
 
         [0024]    Further objects and advantages are to provide a wireless pH monitor for aquariums that is simple to install and remove, provides an easy pH sensor replacement method, can be configured for remote monitoring, and can be configured for data logging of the pH sensor output. Still further objects and advantages of the present invention will become apparent from a consideration of the ensuing detailed description of the invention in conjunction with the accompanying drawings and the appended claims. 
       SUMMARY 
       [0025]    In accordance with the present invention a wireless electronic monitor for pH in an aquarium comprising two devices that sandwich a wall of the aquarium, the interior device transmitting the output of a pH sensor through the wall to the exterior device using frequency modulated pulses of light. 
     
    
     
       DRAWINGS 
       Figures 
         [0026]      FIG. 1  shows a wireless electronic monitor in an exploded view demonstrating how it is used to sandwich a transparent aquarium wall. 
           [0027]      FIG. 2   a  to  2   c  show the components attached to the transmitter electronics housing. 
           [0028]      FIGS. 3   a  and  3   b  show the connection of the pH sensor to complete the sense and transmit assembly (STA). 
           [0029]      FIG. 4  shows the receive and display assembly (RDA) components that are attached to the receiver electronics housing. 
           [0030]      FIG. 5  shows a schematic representation of the wireless monitor configured for measuring pH in an aquarium. 
       
    
    
     DRAWINGS 
     Reference Numerals 
       [0000]    
       
         
           
               6  pH Sensor 
               8  Molded Header 
               10  Transmitter Housing 
               12  Battery Cover 
               14  Transparent Window 
               15  Sense and Transmit Assembly (STA) 
               16  Transparent Tank Wall 
               18  Receiver Housing 
               20  pH Sensor Output Display 
               22  Water Test Button 
               24  Up Arrow Button 
               26  Down Arrow Button 
               28  Alarm Speaker 
               30  Alarm Light 
               32  Faceplate 
               33  Receive and Display Assembly (RDA) 
               34  Ring Magnet 
               36  Infrared Emitter 
               38  Infrared Detector 
               39  Infrared Emitter-Detector Pair 
               40  Electrical Socket Connector 
               42  Transmitter Circuit Board 
               44  Threaded Standoff 
               45  Transmitter Circuit Assembly 
               46  Potting Material 
               48  9 Volt Battery 
               50  Elastomer Battery Seal 
               52  Elastomer Washer 
               54  Thumbscrew 
               56  Elastomer Sensor Connection Seal 
               58  Electrical Pin Connector 
               60  Receiver Circuit Board 
               74  STA Waterproof Boundary 
               76  RDA Waterproof Boundary 
               100  Infrared Detector Power Supply 
               102  Electronic Switch Power Supply 
               104  Electronic Switch 
               106  Electronic Switch Input Voltage Level 
               108  pH Measurement Circuitry Power Supply 
               110  Manual pH Measurement Request 
               112  Central Processing Unit (CPU) 
               114  Single Voltage Pulse 
               116  Single Infrared Light Pulse 
               118  Automatic pH Measurement Request 
               120  Electronic Memory 
               122  Electronic Timer 
               124  Timer Output 
               126  Amplifier Circuit 
               128  pH Sensor Output 
               130  Amplifier Circuit Output 
               132  Floating Reference Circuit 
               134  Voltage Controlled Oscillator Circuit (VCO) 
               136  pH Modulated VCO Input Voltage 
               138  Train of Frequency Modulated Voltage Pulses 
               140  Train of Frequency Modulated Infrared Light Pulses 
               142  pH Modulated Frequency Signal 
               144  Digital pH Value 
               146  Increment Set-Point Signal 
               148  Decrement Set-Point Signal 
               150  Audible Alarm CPU Output 
               152  Visible Alarm CPU Output 
           
         
       
     
       DETAILED DESCRIPTION 
     FIGS.  1  Through  5 -Preferred Embodiment 
       [0092]    The detailed description set forth in connection with the appended drawings is intended as a description of presently preferred embodiments of the invention and is not intended to represent the only forms in which the present invention may be constructed and/or utilized. The description sets forth the functions and the sequence of steps for constructing and operating the invention in connection with the illustrated embodiments. However, it is understood that the same or equivalent functions and sequences may be accomplished by different embodiments that are also intended to be encompassed within the scope of the invention. 
         [0093]    A preferred embodiment of the wireless electronic monitor for a container such as an aquarium is illustrated in  FIG. 1  (exploded view). The monitor is comprised of a sense and transmit assembly (STA)  15  and a receive and display assembly (RDA)  33 . The STA  15  is configured with a pH sensor  6  that is well known as a combination electrode of the type available from Omega Engineering Inc. of Stamford, Conn. However, any other device that exhibits a variable electrical output dependent upon aqueous ionic activity, dissolved gas concentration, or temperature and the like can be used as a transducer for the STA  15 . 
         [0094]    A molded header  8  is cast around the electrical connection end of the pH sensor  6  from a two-part polyurethane or epoxy resin that cures at approximately room temperature. The resin cannot be cured at elevated temperatures or generate significant exothermic heat during the cure because the pH sensor  6  contains air and aqueous solutions that can expand or boil. The header  8  is a watertight electrical and mechanical connection of the sensor  6  to power and signal processing circuits within a transmitter housing  10 . In the preferred embodiment, the pH sensor  6  is detachable from the STA  15  so it can be easily replaced if broken or at the end of its operational life. The transmitter housing  10  and a battery cover  12  are both injection molded from a thermoplastic resin such as acrylonitrile butadiene styrene (ABS), polypropylene or the like. A transparent window  14  allows the transmission of light through an opening in the transmitter housing  10 . The STA  15  is oriented to place the transparent window  14  against the interior side of a transparent wall  16 . A similar opening (not shown) in a receiver housing  18  is aligned line-of-sight with the opening in the transmitter housing  10 . The alignment of the two openings and the location of the wireless monitor on the tank wall  16  is maintained using magnetic clamping force on the wall between the STA  15  and the RDA  33 . 
         [0095]    As shown in  FIG. 1 , the preferred embodiment of the RDA  33  is configured with a pH sensor output display  20 . A water test button  22  prolongs battery life by providing an on-demand measurement and display of pH. An up arrow button  24  and a down arrow button  26  permit set-point adjustments for the desired range of pH. If pH levels are outside of that range, an alarm speaker  28  and an alarm light  30  are activated. The RDA  33  is sealed from potential water spills during aquarium maintenance by a faceplate  32 . The receiver housing  18  and the faceplate  32  of the preferred embodiment are molded from similar thermoplastic materials used for the transmitter housing  10  and the battery cover  12 . 
         [0096]      FIGS. 2   a  to  2   c  show the various components attached to the transmitter housing  10 . As shown in  FIG. 2   a  (exploded isometric view), the transparent window  14  is placed over the opening in the housing  10  and sealed watertight with silicone adhesive (not shown) or the like. A ring magnet  34  made of neodymium or similar high magnetic strength material of the type available from Master Magnetics, Inc. of Castle Rock, Colo. is placed on the window  14  and is mechanically attached to the housing  10  with epoxy adhesive (not shown) or the like. The housing  10  has a molded feature that assists aligning the window  14  and the magnet  34  with the opening in the housing  10 . A transmitter circuit assembly  45  is attached to the magnet  34  with epoxy adhesive or the like. The transmitter housing  10  is then laid on a horizontal surface and filled with a potting material  46  such as polyurethane or silicone rubber to seal the transmitter circuit assembly  45 . 
         [0097]    As illustrated in  FIG. 2   b  (isometric view), the transmitter circuit assembly  45  is partly comprised of an infrared emitter-detector pair  39 , an electrical socket connector  40 , and a transmitter circuit board  42 . The transmitter circuit assembly  45  is configured to place the emitter-detector pair  39  within the center opening of the ring magnet  34  so that light can be emitted or detected through the transparent window  14 . An infrared emitter  36 , an infrared detector  38 , and the socket connector  40  are well known electronic components of the type available from Digi-Key Corporation of Thief River Falls, Minn. Other electronic components comprising the transmitter circuit assembly  45  are not shown for clarity. A transmitter circuit board  42  is drilled with holes to create locations to insert a threaded stand-off  44  made of stainless steel or aluminum. As shown in  FIG. 2   c , the potting material  46  fills the transmitter housing  10  cavity to just below the openings in the stand-off  44  and the socket connector  40 . 
         [0098]    Referring to  FIG. 2   a , a rectangular recess is cast into the potting  46  by using a block of compliant material such as silicone rubber (not shown) to form the recess when the liquid potting  46  is dispensed or poured into the transmitter housing  10 . After the potting material  46  hardens, the rubber block is removed, and a 9 volt battery  48  is placed in the recess and connected to the transmitter assembly  45  using a well known 9 volt battery connector (not shown). The battery  48  is kept dry using an elastomer battery seal  50  and an elastomer washer  52  molded from silicone rubber or the like. By hand tightening a plastic thumbscrew  54  into the threaded stand-off  44  at each end of the battery cover  12 , the battery  48  is kept dry. The plastic thumbscrew  54  is designed to preferentially fail if over-tightened into the metal threaded stand-off  44 . 
         [0099]      FIGS. 3   a  (exploded isometric view) and  3   b  (isometric view) show the connection of the pH sensor  6  with the molded header  8  to the assembly shown in  FIG. 2   c . Referring to  FIG. 3   a , an elastomer sensor connection seal  56  is molded from silicone rubber or the like to seal the gap between the molded header  8  and the hardened potting material  46 . An electrical pin connector  58  is partially encapsulated in the molded header  8  and inserted into the socket connector  40  openings (shown in  FIG. 2   c ). By tightening a third thumbscrew  54  into a third threaded standoff  44  (shown in  FIG. 2   c ), the seal  56  is compressed into the surface of the cured potting material  46 . Another washer  52  maintains a waterproof seal of the socket connector  40  and the pin connector  58 .  FIG. 3   b  shows the fully assembled and sealed STA  15  ready to submerge in water. 
         [0100]    As shown in  FIG. 4  (exploded isometric view), the RDA  33  also contains the transparent window  14  and the ring magnet  34 . Both are attached to a feature molded into the receiver housing  18  in a manner similar to the method used for the transmitter housing  10 . A receiver circuit board  60  is configured with the emitter-detector pair  39  (not shown) and is mechanically attached to the ring magnet  34  with epoxy or similar adhesive. Other electronic components on the receiver circuit board  60  and the battery power supply for the RDA  33  are not shown for clarity. 
         [0101]    Additionally, the preferred embodiment integrates the water test button  22 , the up arrow button  24 , and the down arrow button  26  into a well known membrane switch (not shown) of the type available from Nelson Nameplate of Los Angeles, Calif. The membrane switch is fabricated from laminated sheets of polyester or polycarbonate, to which conductive and colored inks are applied. Switches, light emitting diodes, regions of transparency for viewing underlying displays, and artwork can be combined into a very flat structure that is rugged and has low fabrication costs. The membrane switch is attached to the faceplate  32  typically using tape backed with acrylic adhesive or the like to provide a sealed keypad that is waterproof. Electrical contact of such a membrane switch to an electrical connection on the receiver circuit board  60  is typically done with a pigtail formed in the laminated sheets (not shown). 
         [0102]    A schematic representation of the wireless monitor of pH for an aquarium is illustrated in  FIG. 5 . Clearly shown is the demarcation of the two main assemblies, with the STA  15  on the internal water side of the tank wall  16 , and the RDA  33  on the external air side. An STA waterproof boundary  74  is formed around the electronics contained within the STA  15 , leaving the water sensing end of the pH sensor  6  exposed to the water. Similarly, an RDA waterproof boundary  76  is formed around the electronics contained within the RDA  33 . 
         [0103]      FIG. 5  shows that the battery  48  provides an infrared detector power supply  100  to the infrared detector  38  contained in the STA  15 . The battery  48  also provides an electronic switch power supply  102  to an electronic switch  104 . When the infrared detector  38  is not illuminated above a set light threshold level, an electronic switch input voltage level  106  is configured to keep the switch  104  open. The open switch  104  prevents consumption of a pH measurement circuitry power supply  108  during periods of time when a pH measurement is not desired. 
         [0104]    When a pH measurement is desired,  FIG. 5  shows two methods by which it may be requested. Using the RDA  33 , a manual pH measurement request  110  can be sent to a central processing unit (CPU)  112  by pressing the water test button  22 . The CPU  112  sends a single voltage pulse  114  to the infrared emitter  36  within the RDA  33 , causing it to emit a single infrared light pulse  116 . An automatic pH measurement request  118  uses stored times or time periods accessed from an electronic memory  120  by the CPU  112  to initiate the single light pulse  116 . 
         [0105]    The single pulse of infrared light  116  transmits through the transparent window  14  in the RDA  33 , through the transparent wall  16 , through the transparent window  14  in the STM  15 , and illuminates the infrared detector  38  within the STA  15 . During the period that the detector  38  is illuminated by the light pulse  116 , the switch input voltage level  106  is configured to close the open switch  104 . 
         [0106]    For the duration of the light pulse  116 , the pH measurement circuitry power supply  108  is connected to an electronic timer  122  that self-starts immediately. A timer output  124  is connected to the switch input voltage level  106  to hold the switch  104  closed after the duration of the single light pulse  116  has elapsed, and will remain closed for the duration that the timer  122  is on. While the electronic timer  122  is on, the pH measurement power supply  108  is connected to the timer  122 . When the timer  122  reaches the end of the specified on period, the timer output  124  is configured to open the switch  104  and eliminate its own power supply  108 . The timer  122  will not re-start until the single infrared light pulse  116  requests another pH measurement. 
         [0107]    During the period that the timer  122  is on, the pH measurement circuitry power supply  108  is turned on to the rest of the circuitry on the transmitter circuit assembly  45  (shown in  FIG. 2   b ). In the preferred embodiment, an amplifier circuit  126  and the pH sensor  6  of  FIG. 5  are placed close together and encapsulated in the molded header  8  (shown in  FIGS. 3   a  and  3   b ). An amplifier circuit output  130  shown in  FIG. 5  is connected to the transmitter circuit assembly  45  by the socket connector  40  (shown in  FIGS. 2   a  to  2   c ), and the pin connector  58  (shown in  FIG. 3   a ). 
         [0108]    Referring again to  FIG. 5 , a floating reference circuit  132  places the reference potential for the pH sensor  6  and the amplifier circuit  126  at approximately 3 volts, or about one third of the 9 volt battery  48  potential. This is required because the pH sensor can be a positive or negative voltage. The gain of the amplifier  126  is configured so that negative voltage levels at the amplifier output  130  do not go more than about 2 volts below the reference potential for all expected values of pH to be measured. A voltage controlled oscillator circuit (VCO)  134  receives a pH modulated VCO input voltage  136  that will always be positive and indicative of the pH sensor output  128 . By placing the reference potential at approximately 3 volts and limiting the amplifier output  130  to about plus or minus 2 volts relative to that reference, the battery  48  can be used when depleted to as low as 5 volts. 
         [0109]    The VCO  134  converts the pH dependent VCO input voltage  136  into a train of frequency modulated voltage pulses  138 . The voltage pulses  138  drive the infrared emitter  36  in the STA  15  to emit a train of frequency modulated light pulses  140 . The light pulses  140  are transmitted through the transparent window  14  in the STA  15 , the transparent tank wall  16 , and the transparent window  14  in the RDA  33 . The infrared detector  38  in the RDA  33  is illuminated by the train of light pulses  140  and generates a pH modulated frequency signal  142  that is sent to the CPU  112 . The frequency of the signal  142  is compared with a calibration look-up table in the electronic memory  120  that is obtained by measuring the frequency of the pH modulated signal  142  when the pH sensor  6  is immersed into a standard solution of known pH for two or more pH values. A digital pH value  144  of the current pH within the tank is sent to the pH sensor output display  20  and provides a visible numeric pH value. 
         [0110]    By using the up arrow button  24  and the down arrow button  26  to adjust upper and lower bounds for acceptable pH, set-point values are stored in the electronic memory  120 . The ability to send an increment set-point signal  146  or a decrement set-point signal  148  to the CPU  112  permits adjustable alarm levels for aquarium pH. The CPU  112  is programmed to periodically make an automatic pH measurement request  118  and initiate a pH measurement in the manner shown in  FIG. 5 . The pH modulated frequency signal  142  obtained from the periodic measurement is evaluated by the CPU  112  programming to ascertain whether the pH of the water contained in the tank is outside of two limit values stored in electronic memory  120 . If the pH is outside of the pre-defined limits, an audible alarm CPU output  150  will activate the alarm speaker  28 . A versatile alarm system includes a visible alarm CPU output  152  to activate the alarm light  30  when an aquarium owned by a hearing impaired person requires attention. 
       Operation—FIGS. 1,  2 , and  5   
       [0111]    The manner of using the wireless monitor is to immerse the STA  15  into the aquarium water and place the side with the transparent window  14  against the transparent wall  16  of the tank. Holding the STA  15  against the interior surface of the wall  16  with one hand, the transparent window  14  in the RDA  33  is placed against the exterior surface of the wall  16  using the other hand. Sliding the RDA  33  or the STA  15  against their respective surfaces of the wall  16 , the two windows  14  are brought into approximate line-of-sight alignment until the magnet  34  in each attract one another. When the magnetic attraction between the STA  15  and the RDA  33  is sufficient to hold them in place on the tank wall  16 , they are released and rely on friction to maintain their position. When the wall  16  is sandwiched between the STA  15  and the RDA  33 , the position of this invention can be adjusted as desired by grasping the RDA  33  and sliding it on the exterior surface of the wall  16 . Held in place by magnetic attraction, the STA  15  will slide along the interior surface of the tank wall  16  and follow the movement to the desired wall  16  location for the wireless monitor. This makes it a simple process to sandwich the wall  16  with the STA  15  and the RDA  33  near the surface of the water and move it to a deeper location on the transparent wall  16 . 
         [0112]    To make a pH measurement, the water test button  22  is manually pushed. The RDA  33  will send a single light pulse  116  to the STA  15  that will activate the timer  122  and turn the pH measurement circuit power supply  108  on for a pre-determined amount of time. For that period of time, a train of frequency modulated infrared light pulses  140  are transmitted from the STA  15  to the RDA  33 . The CPU  112  will sample the pH modulated frequency signal  142  for the time required to obtain an accurate average of its frequency. That frequency is converted to a digital pH value  144  that is then shown in the monitor display  20  as a numerical value of pH for a pre-determined amount of time. 
         [0113]    To calibrate the pH sensor  6  or to adjust alarm set-points, there are numerous ways to indicate to the CPU  112  that such an action is desired. Simultaneously pressing the up arrow button  24  and the down arrow button  26 , or the addition of specific buttons to the faceplate  32  are only two ways that can be employed. The specific mechanism by which the look-up table in electronic memory  120  that contains calibration constants and set-point pH values is updated is beyond the scope of the present invention. Because this invention is clearly described as dependent upon the CPU  112  and the electronic memory  120 , the reader can see that the specificities of software programming are not necessary to provide full disclosure. 
       Additional Embodiments 
       [0114]    There are a number of water parameters that can be sensed using a probe similar to the pH sensor of this invention. Ions that are of interest to aquarium owners are reflected in the commercial availability of colorimetry kits that test for ammonia, nitrate, nitrite, hardness and alkalinity. All of the ions measured by the colorimetry kit can be measured by similar electrodes used to measure pH, and thus can be directly used by the wireless monitor. Dissolved oxygen sensors, conductivity cells for salinity, and temperature sensors such as a thermistor are also readily adapted to the wireless monitor for aquariums. 
         [0115]    The preferred embodiment of this invention describes a single sensor, specifically for measuring pH. In practice, this invention can be embodied with multiple sensors. A second device such as a temperature sensor can easily be attached to the described transmitter circuit assembly and provide monitoring of yet another important water parameter for aquariums and the like. 
         [0116]    The wireless monitor can be configured with a sensor for a fluid such as a gas, enabling this invention to be used to measure moisture, flammable or explosive gas levels, and oxygen in a closed container such as a glove-box. 
         [0117]    Configured with a radiation sensor, this invention can be used for radioactive applications where the wireless monitor can be placed on a glove-box viewing window or the leaded glass of a radioactive waste storage chamber. 
         [0118]    This invention as described is used on an aquarium having a transparent wall of glass, acrylic or the like. In the case of an opaque tank made of a material such as fiber-filled polypropylene or polyethylene, the infrared light used to convey the sensor information would not transmit through the wall. In such a case, this invention would be useful using another form of energy to transmit the pulses that initiate of a pH measurement and subsequent pH sensor output. Such forms of energy include, but are not limited to:
       1. a fluctuating magnetic field for a tank wall material that does not form a Guassian shield, such as a fiber-filled thermoplastic or thermoset polymer, copper, and some stainless steels;   2. radio or microwave frequency radiation for a non-metallic tank wall where the conductivity of the liquid within does not significantly affect the signal strength; and   3. acoustic energy to transmit the sensor output through tank walls made of a material that interposes a Gaussian shield between the STA and the RDA.       
 
         [0122]    The method by which this invention can be attached to the tank wall and maintain the location in which it was placed is shown to be the mutual attraction of two magnets in the preferred embodiment. This method works best when the wall thickness is less than approximately one half inch. For a wall that is significantly thicker, this invention is useful if the STA and the RDA are attached directly to the wall using a suction cup or similar device. In applications where there are large fish that could knock the STA off from the interior wall or other turbulent scenarios, it can be attached directly to the tank wall using an adhesive such as silicone or epoxy. When using the monitor in public places, permanent attachment of the RDA to the exterior wall of the tank may be required to prevent theft. 
         [0123]    The present invention can be used on a container such as a bag made of polyethylene, polyethylene terephthalate (PET), or similar material. 
         [0124]    The encapsulation with the potting material of the transmitter circuit assembly can be obviated using housing structures that incorporate rubber seals and the like. 
         [0125]    The frequency modulated voltage pulses and subsequent frequency modulated light pulses can be configured in pattern conforming to a standard serial communication format such as RS-232 or similar. 
         [0126]    The detachable sensor shown in the preferred embodiment can be incorporated directly into the STA if the operational life is considered permanent, such as a thermocouple, thermistor, or conductivity cell and the like. 
         [0127]    This invention finds great usefulness when configured with access to the Internet or a wireless cellular phone network to send the measurement results of many tanks to a central monitoring location. 
         [0128]    By storing the measurement results in electronic memory for later retrieval, this invention is useful in applications such as shipment of live aquatic specimens and other records of water fitness over time. 
         [0129]    This invention can be configured in many shapes other than rectangular, including but not limited to circular, square, triangular, or an iconic shape such as an aquatic life form, logo or decorative representation. 
       Advantages 
       [0130]    From the description above, a number of advantages of this wireless electronic monitor for containers such as aquariums become evident:
       1. An aquarium can be monitored around the clock for pH.   2. This invention generates an audible and visible alert if the pH of the water is outside of expected boundaries.   3. This invention is easy to install on the wall of a tank near the surface the water and can be moved to a deeper location without inserting the hand or arm into the water.   4. A pH dependent electrical signal gives the opportunity to use a CPU to manage sensor calibration, activate alarms, and store measurement results.   5. The wireless electronic monitor has a broader test range and finer resolution of measurement than colorimetry pH measurements.   6. This invention is simple to use and less intrusive for aquarium applications than laboratory and industrial pH monitoring equipment presently available.   7. Sandwiching the wall of a container such as a tank or aquarium permits this invention to operate in saltwater because the transmission medium is the wall material, not the liquid contained in the tank.       
 
       CONCLUSIONS, RAMIFICATIONS, AND SCOPE 
       [0138]    Accordingly, the reader will see that the wireless electronic monitor can be configured with a sensor other than for pH, can use two or more sensors together such as pH and temperature, and can be configured with a sensor for gases, vapors or radioactivity. Also, this invention can use forms of energy other than light to communicate sensor output, can also be attached to a container wall with suction generating devices or adhesive, can be configured with access to distributed communications-networks to monitor multiple tanks from a remote location, and can be configured to store periodic measurement results in the electronic memory to serve as a data logger. Additional embodiments use modulated light pulses that conform to a serial communication standard, integrate the sensor into the sense and transmit assembly (STA), and can have various shapes. 
         [0139]    Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. While the invention has been described in connection with certain preferred embodiments, it is not intended to limit the scope of the invention to the particular forms set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the scope of the invention as defined by the claims.