Patent Publication Number: US-9427097-B2

Title: Refrigeration control using a door handle proximity sensor

Description:
BACKGROUND 
     This section is intended to provide a background or context to the invention recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section. 
     The present invention relates generally to the field of temperature-controlled display devices (e.g. refrigerated display devices or cases, etc.) having a temperature-controlled space for storing and displaying products such as refrigerated foods or other perishable objects. More specifically, the present invention relates to a control system for operating a temperature-controlled display device. More specifically still, the present invention relates to a control system for a temperature-controlled display device that uses sensory input from a proximity sensor integrated with the display case door handle to control conditions within the temperature-controlled space. 
     Temperature-controlled display devices (e.g., refrigerators, freezers, refrigerated merchandisers, refrigerated display cases, etc.) may be used in commercial, institutional, and residential applications for storing or displaying refrigerated or frozen objects. For example, refrigerated display cases can be used to display fresh food products (e.g., beef, pork, poultry, fish, etc.) in a supermarket or other commercial setting. 
     Refrigerated display cases typically include cooling elements (e.g. cooling coils, heat exchangers, evaporators, etc.) that receive a coolant (e.g. a liquid such as a glycol-water mixture, a refrigerant, etc.) from a cooling system (e.g., a refrigeration system) to provide cooling to the temperature-controlled space. Some refrigerated display cases include fans that can be used to move air over the cooling elements to facilitate heat transfer thereto. Fans may also be used to create an air barrier (e.g., an air curtain) to prevent outside air from entering the temperature-controlled space. 
     Some refrigerated display cases have doors that can be opened (e.g., by a customer) to access products within the temperature-controlled space. The position of the doors (i.e., open or closed) can be detected using a variety of well-known sensors. However, current refrigerated display cases are unable to anticipate when the doors are about to be opened and therefore are unable to preemptively implement different control strategies prior to the doors being physically opened. 
     Accordingly, it would be desirable to provide a refrigerated display device or case with the ability to detect when the doors are about to be opened that would overcome these and other disadvantages. 
     SUMMARY 
     One implementation of the present disclosure is a temperature-controlled display device. The temperature-controlled display device includes a temperature-controlled space and a refrigeration circuit configured to provide cooling for the temperature-controlled space. The refrigeration circuit is configured to operate in multiple cooling modes including a normal refrigeration mode and an anti-ingression mode. The temperature-controlled display device further includes a door having a handle configured to facilitate movement of the door between a closed position and an open position for accessing items within the temperature-controlled space and a proximity sensor configured to detect an object within a detection zone adjacent to the handle. In some embodiments, the proximity sensor is a projected capacitive sensor integrated with the handle. The temperature-controlled display device further includes a controller configured to estimate a distance between the handle and the object using an input from the proximity sensor. The controller is configured to cause the refrigeration circuit to transition between the multiple cooling modes based on the estimated distance. In some embodiments, the controller causes the refrigeration circuit to transition from the normal refrigeration mode into the anti-ingression mode in response to a determination that the estimated distance is less than a threshold value. 
     Another implementation of the present disclosure is a method for operating a temperature-controlled display device. The method includes detecting an object within a detection zone adjacent to a handle of the temperature-controlled display device. The handle is attached to a door of the temperature-controlled display device and configured to facilitate movement of the door between a closed position and an open position for accessing items within a temperature-controlled space. The method further includes estimating a distance between the handle and the object using an input from a proximity sensor and causing a refrigeration circuit of the temperature-controlled display device to transition between multiple cooling modes based on the estimated distance. The multiple cooling modes include a normal refrigeration mode and an anti-ingression mode. 
     Another implementation of the present disclosure is a temperature-controlled display device. The temperature-controlled display device includes a refrigeration circuit configured to provide cooling for a temperature-controlled space and to operate in multiple cooling modes. The temperature-controlled display device further includes a door having a handle configured to facilitate movement of the door between a closed position and an open position for accessing items within the temperature-controlled space and a projected capacitive sensor integrated with the handle. The projected capacitive sensor is configured to detect a hand or forearm of a user reaching for the handle. The temperature-controlled display device further includes a controller configured to cause the refrigeration circuit to transition between the multiple cooling modes in response to a detecting the hand or forearm of the user reaching for the handle. 
     The foregoing is a summary and thus by necessity contains simplifications, generalizations, and omissions of detail. Consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices and/or processes described herein, as defined solely by the claims, will become apparent in the detailed description set forth herein and taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a temperature-controlled display device having a plurality of doors and handles, according to an exemplary embodiment. 
         FIG. 2  is a cross-sectional elevation view of the temperature-controlled display device of  FIG. 1  showing a temperature-controlled space and a fan configured to provide chilled air to the temperature-controlled space, according to an exemplary embodiment. 
         FIG. 3  is a block diagram of a refrigeration circuit that may be used by the temperature-controlled display device of  FIG. 1  to provide cooling for the temperature-controlled space, according to an exemplary embodiment. 
         FIG. 4  is an elevation view of one of the handles of  FIG. 1  showing an electrical connection between the handle and a voltage source and an electric field emanating in all directions from the handle, according to an exemplary embodiment. 
         FIG. 5  is an elevation view of one of the handles of  FIG. 1  showing an electromagnetic shield surrounding a shielded portion of the handle such that the electric field emanates only from an unshielded portion of the handle, according to an exemplary embodiment. 
         FIG. 6  is a cross-section of the handle shown in  FIG. 4  taken at the line A-A, showing an electrically-conductive core within the handle and an electric field emanating in all directions from the handle, according to an exemplary embodiment. 
         FIG. 7  is a cross-section of the handle shown in  FIG. 5  taken at the line B-B, showing an electrically-conductive core and an electromagnetic shield maintained at the same voltage as the core surrounding the core on all sides such that any conductor external to the handle forms an electric field with the shield and not the core, according to an exemplary embodiment. 
         FIG. 8  is a cross-section of the handle shown in  FIG. 5  taken at the line C-C, showing the electrically-conductive core and an electromagnetic shield maintained at the same voltage as the core surrounding some but not all of the core to direct the electric field emanating from the core only toward a detection zone in front of the handle, according to an exemplary embodiment. 
         FIG. 9  is a circuit diagram illustrating a projected capacitive sensor that may be integrated with the handle of  FIG. 1  for detecting an object such as a human hand or forearm in the detection zone in front of the handle, according to an exemplary embodiment. 
         FIG. 10  is a block diagram of a controller that may be used to control the temperature-controlled display device of  FIG. 1 , according to an exemplary embodiment. 
         FIG. 11  is a flowchart of a process for operating the temperature-controlled display device of  FIG. 1 , according to an exemplary embodiment. 
         FIGS. 12-14  are circuit diagrams illustrating circuit elements that may be used to apply a voltage to the handle of  FIG. 1  and to measure a capacitance associated with the handle, according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring generally to the FIGURES, a refrigerated display case with a door handle proximity sensor is shown, according to an exemplary embodiment. The refrigerated display case includes a temperature-controlled space for storing and displaying objects such as refrigerated foods or other perishable objects. The refrigerated display case includes a door and a handle attached to the door for accessing objects stored within the temperature-controlled space. 
     The refrigerated display uses a proximity sensor to detect the presence of an object within a detection region near the door handle. The proximity sensor may use projected capacitance or any other type of proximity detection technology to anticipate when the display case door is about to be opened. For example, a capacitive sensor may be integrated with the door handle and may be used to detect the presence of a human hand reaching for the door handle. 
     In some embodiments, the sensor includes an electrode, a plate, or another electrically-conductive object defining one half of a capacitor. The sensor may project an electromagnetic field into a detection region near the door handle and may produce a signal indicating a capacitance relative to ground. An electromagnetic field absorbing object (e.g., a hand, forearm, or other body part of a user) within the detection region may effectively form the second half of the capacitor such that movement of the object toward or away from the capacitive sensor changes the measured capacitance. 
     A controller for the refrigerated display case uses a signal from the proximity sensor to estimate the distance between the door handle and the hand of a customer. The controller anticipates the display case door being opened (e.g., by comparing the estimated distance with a threshold value) and preemptively initiates a different mode of operation in response to a determination that the display case door is about to be opened. For example, the controller may cause one or more components of a refrigeration system for the refrigerated display case to shift into a more aggressive operating mode in anticipation of the display case door being opened. In some embodiments, shifting into the more aggressive operating mode includes increasing the speed of a display case fan to prevent the ingression of ambient air into the temperature-controlled space. Advantageously, the use of the proximity sensor allows the more aggressive operating more to be initiated at an optimal time prior to the display case door being opened. 
     Referring now to  FIGS. 1-2 , a temperature-controlled display device  10  is shown, according to an exemplary embodiment. Temperature controlled-display device  10  may be a refrigerator, a freezer, a refrigerated merchandiser, a refrigerated display case, or other device capable of use in a commercial, institutional, or residential setting for storing and/or displaying refrigerated or frozen objects. For example, temperature-controlled display device  10  may be a service type refrigerated display case for displaying fresh food products (e.g., beef, pork, poultry, fish, etc.) in a supermarket or other commercial setting. 
     Temperature-controlled display device  10  is shown to include a plurality of doors  12  and a case  14 . Doors  12  and case  14  at least partially define a temperature-controlled space  20  within which refrigerated or frozen objects can be stored. Temperature-controlled space  20  is shown to include a plurality of shelves  22  upon which refrigerated or frozen objects can be placed for storage and/or display. Doors  12  may define the front of temperature-controlled space  20  and case  14  may define the top, bottom, sides, and/or back of temperature-controlled space  20 . In some embodiments, doors  12  are insulated glass doors including one or more transparent panels such that the objects within temperature-controlled space  20  can be viewed through doors  12  (i.e., from the exterior of display device  10 ) when doors  12  are closed. 
     Doors  12  may be configured to move between a closed position and an open position. In the closed position (shown in  FIG. 1 ), doors  12  may prevent access to temperature-controlled space  20  and may contain chilled air within temperature-controlled space  20 . In the open position, doors  12  may permit access to temperature-controlled space  20  to such that the refrigerated or frozen objects can be loaded into and/or removed from temperature-controlled space  20 . As shown in  FIG. 1 , doors  12  may be rotatably connected to case  14  along axes  16  and may be configured to rotate about axes  16  between the closed position and the open position. In other embodiments, doors  12  may be sliding doors or panels configured to slide between the closed position and the open position. 
     Still referring to  FIGS. 1-2 , temperature-controlled display device  10  is shown to include handles  18 . Handles  18  may be attached to doors  12  to facilitate moving doors  12  between the closed position and the open position. In some embodiments, handles  18  are attached to a front surface of doors  12 . 
     Handles  18  may include proximity sensors integrated therewith. In various embodiments, the proximity sensors may be located inside handles  18 , attached to handles  18 , installed near handles  18 , or otherwise positioned to monitor a detection zone near handles  18 . The proximity sensors may be capacitive sensors (e.g., projected capacitive, mutual capacitive, self-capacitive, etc.) or other type of sensor (e.g., optical, microwave, ultrasound, magnetic, photoelectric, inductive, Doppler effect, sonar, radar, Eddy-current, etc.) configured to detect the presence of a customer&#39;s hand or forearm in a detection zone near handles  18  and/or touching handles  18 . The proximity sensors and the operation thereof is described in greater detail with reference to  FIGS. 4-8 . 
     Referring specifically to  FIG. 2 , temperature-controlled display device  10  is shown to include a cooling element  24  and a fan  26 . Cooling element  24  may include a cooling coil, a heat exchanger, an evaporator, or other component configured to provide cooling for temperature-controlled space  20 . Cooling element  24  may be part of a refrigeration circuit (e.g., refrigeration circuit  50 , shown in  FIG. 3 ) and may be configured to absorb heat from an airflow  28  passing over or through cooling element  24 . 
     Fan  26  may be configured to cause airflow  28  through cooling element  24 . In some embodiments, fan  26  causes airflow  28  is from cooling element  24  through a channel  30  along a rear surface  38  and/or upper surface  40  of temperature-controlled space  20 . Rear surface  38  and/or upper surface  40  may include a plurality of outlets distributed along channel  30  (e.g., holes in rear surface  38  and upper surface  40  into channel  30 ) through which airflow  28  can pass from channel  30  into temperature-controlled space  20 . 
     Still referring to  FIG. 2 , channel  30  is shown to include an outlet  32  configured to direct airflow  28  downward from a front end of channel  30 . The downward airflow from outlet  32  may form an air curtain  36  between outlet  32  and inlet  34 . When door  12  is opened, air curtain  36  may help retain chilled air within temperature-controlled space  20  and may prevent the ingression of ambient air (e.g., warmer air from outside display device  10 ) into temperature-controlled space  20 . When door  12  is closed, door  12  may seal temperature-controlled space  20  from the ambient environment outside display device  10  and may reduce or eliminate the utility of air curtain  36 . 
     Air curtain  36  may be created by operating fan  26 . The optimal time to create air curtain  36  may be before door  12  is opened so that air curtain  36  can be fully established by the time door  12  is opened. Advantageously, the proximity sensor integrated with handle  18  can detect when door  12  is about to be opened by detecting a user&#39;s hand or forearm in a detection zone near handle  18 . Fan  26  may be activated or increased in speed (e.g., by a controller) in response to a determination that door  12  is about to be opened using input from the proximity sensor. Anticipating the opening of door  12  allows air curtain  36  to be fully established prior to opening door  12 . 
     Temperature-controlled display device  10  may be operated in multiple different modes. When door  12  is closed, temperature-controlled display device  10  may be operated in a refrigeration mode to maintain conditions (e.g., temperature, humidity, air pressure, etc.) within temperature-controlled space  20  at a setpoint or within a setpoint range. When door  12  is opened or about to be opened, temperature-controlled display device  10  may be operated in a more aggressive mode to prevent the ingression of ambient air into temperature-controlled space  20  (e.g., increasing the speed of fan  26  to form air curtain  36 , establishing a pressure gradient within temperature-controlled space  20 , activating additional fans or cooling elements, etc.). Temperature-controlled display device  10  may determine when door  12  is about to be opened using input from the proximity sensor integrated with handle  18  and may transition from the refrigeration mode into the more aggressive mode in response to such a determination. 
     Referring now to  FIG. 3 , a refrigeration circuit  50  that may be used by temperature-controlled display device  10  is shown, according to an exemplary embodiment. Refrigeration circuit  50  is shown to include compressors  42 , heat exchangers  48 , expansion valves  44 , and cooling elements  24 . Compressors  42  may be configured to circulate a coolant (e.g. a liquid such as a glycol-water mixture, a refrigerant, etc.) through refrigeration circuit  50 . In some embodiments, compressors  42  are operated by controller  54 . For embodiments in which the coolant is a compressible refrigerant, compressors  42  may compress the refrigerant to a high pressure, high temperature state and discharge the compressed refrigerant into line  56 . Line  56  is shown connecting the outlet of compressors  42  to the inlet of heat exchangers  48 . 
     Heat exchangers  48  may be configured to cool the compressed refrigerant in line  56 . In various embodiments, heat exchangers  48  may be gas coolers (i.e., heat exchangers configured to remove heat from gaseous refrigerant without causing condensation) or condensers (i.e., heat exchangers configured to condense a gaseous refrigerant to a liquid or mixed gas-liquid state). In some embodiments, heat exchangers  48  are heat-reclaim heat exchangers configured to use the heat absorbed from the compressed refrigerant for heating purposes (e.g., heating water, providing heat to a space, melting frost or ice, anti-condensate heating for display device  10 , etc.). Heat exchangers  48  may be configured to transfer heat from the compressed refrigerant into another fluid circulating through heat exchangers  48  (e.g., another refrigerant, a separate refrigeration circuit, etc.) or into the ambient environment. In some embodiments, refrigeration circuit  50  includes fluid control valves immediately upstream or downstream of heat exchangers  48  to direct the refrigerant through a subset of heat exchangers  48 . 
     In some embodiments, refrigeration circuit  50  includes fans  46  configured to cause an airflow  52  through or across heat exchangers  48 . Fans  46  may be controlled by controller  54  to modulate the rate of heat transfer in heat exchangers  48 . In some embodiments, fans  46  are variable speed fans capable of operating at multiple different speeds. Controller  54  may increase or decrease the speed of fans  46  in response to various inputs from refrigeration circuit  50  (e.g., temperature measurements, humidity measurements, enthalpy measurements, etc.). 
     Still referring to  FIG. 3 , line  58  is shown connecting an outlet of heat exchangers  48  to an inlet of expansion valves  44 . Expansion valves  44  may be configured to expand the refrigerant in line  58  to a low temperature and low pressure state. Expansion valves  44  may be fixed position valves or variable position valves. Expansion valves  44  may be actuated manually or automatically (e.g., by controller  54  via a valve actuator) to adjust the expansion of the refrigerant passing therethrough. In some embodiments, expansion valves  44  may be operated as fluid control valves to direct the refrigerant through a subset of cooling elements  24 . Expansion valves  44  may output the expanded refrigerant into line  60 . Line  60  is shown extending from an outlet of expansion valves  44  to an inlet of cooling elements  24 . 
     Cooling elements  24  may be the same as previously described with reference to  FIG. 2 . For example, cooling elements  24  may include cooling coils, heat exchangers, evaporators, or other components configured to provide cooling for temperature-controlled space  20 . Cooling elements  24  may be configured to absorb heat from an airflow  28  passing over or through cooling elements  24 . Cooling elements  24  may output the refrigerant into line  62 , which connects to the suction side of compressors  42 . 
     In some embodiments, refrigeration circuit  50  includes fans  26  configured to cause an airflow  28  through or across cooling elements  24 . Fans  26  may be controlled by controller  54  to modulate the rate of heat transfer from temperature-controlled space  20  into cooling elements  24 . In some embodiments, fans  26  are variable speed fans capable of operating at multiple different speeds. Controller  54  may increase or decrease the speed of fans  26  in response to various inputs from refrigeration circuit  50  (e.g., temperature measurements, humidity measurements, enthalpy measurements, etc.). 
     Fans  26  may be configured to generate an air curtain  36 , to establish a pressure gradient, and/or generate a pressure differential within temperature-controlled space  20 , as described with reference to  FIG. 2 . Fans  26  may be activated, deactivated, or speed modulated by controller  54  to transition between a normal refrigeration mode (e.g., a relatively lower fan speed) and a more aggressive air ingression prevention mode (e.g., a relatively higher fan speed). 
     Still referring to  FIG. 3 , refrigeration circuit  50  is shown to include a controller  54 . Controller  54  may be configured to operate various components of refrigeration circuit  50  to provide refrigeration for temperature-controlled space  20 . For example, controller  54  may operate compressors  42 , fans  46 , valves  44 , fans  26 , and/or other operable components of refrigeration circuit  50  (e.g., flow control valves, pressure regulation valves, etc.) to circulate a fluid refrigerant between heat exchangers  48  and cooling elements  24 . Controller  54  may also control other components of display device  10  such as an anti-condensate heaters, a lighting element, a condensate dissipation system, and/or other auxiliary components of display device  10 . 
     Controller  54  may receive input from various sensory devices of refrigeration circuit  50  (e.g., temperature sensors, humidity sensors, pressure sensors, enthalpy sensors, voltage sensors, proximity sensors, etc.) Sensors may be disposed at any location relative to temperature-controlled display device  10  and/or refrigeration circuit  50 . For example, sensors may be positioned along any of lines  56 - 62 , within temperature-controlled space  20 , integrated with door handle  18 , or otherwise positioned to measure any variable state or condition of temperature-controlled display device  10 . Controller  54  may use the sensory inputs to determine appropriate control outputs for the operable components of refrigeration circuit  50 . 
     Controller  54  may be configured to detect the presence of an object (e.g., a human hand or forearm) in a detection zone near handle  18 . In some embodiments, handle  18  includes a projected capacitive sensor. Handle  18  may form one half of the capacitor and the detected object may form the other half of the capacitor. Controller  54  may calculate the capacitance of the capacitor by applying an alternating voltage to door handle  18  (e.g., to an internal conductor within handle  18 , covered by an insulating shell) and measuring an alternating current between the voltage source and handle  18 . 
     Controller  54  may use the calculated capacitance to estimate the distance between handle  18  and the detected object and to determine when door  12  is about to be opened. For example, controller  54  may determine that door  12  is about to be opened in response to a determination that the estimated distance between handle  18  and the detected object is less than a threshold value. 
     Controller  54  may operate refrigeration circuit  50  in multiple different modes including a normal refrigeration mode and a more aggressive anti-ingression mode. In the refrigeration mode, controller  54  may operate refrigeration circuit  50  to maintain conditions (e.g., temperature, humidity, air pressure, etc.) within temperature-controlled space  20  at a setpoint or within a setpoint range. Controller  54  may respond to a determination that door  12  is about to be opened by shifting into the anti-ingression mode. In the anti-ingression mode, controller  54  may operate refrigeration circuit  50  to prevent the ingression of ambient air into temperature-controlled space  20 . For example, in the anti-ingression mode, controller  54  may increase the speed of fans  26  to form air curtain  36 , establish a pressure gradient within temperature-controlled space  20 , activate additional fans or cooling elements, and/or perform other control operations designed to maintain conditions within temperature-controlled space  20  when door  12  is opened. Controller  54  is described in greater detail with reference to  FIG. 10 . 
     Referring now to  FIGS. 4-8 , handle  18  is shown in greater detail, according to various exemplary embodiments. Handle  18  may be attached to a front surface of door  12  such that handle  18  can be used to open and close door  12  from the exterior of temperature-controlled display device  10 . In various embodiments, handle  18  may be a curved handle (as shown in  FIGS. 4-5 ), a lever, a door knob, a hand grip, a flat panel (e.g., for push-to-open doors), a bar, or may have any other shape or configuration such that handle  18  can be touched or gripped to open door  12 . 
     Referring specifically to  FIGS. 4-5 , handle  18  may be formed at least partially from an electrically-conductive material. Handle  18  may be electrically connected to a voltage source  68  configured to apply a voltage V(t) to handle  18 . In some embodiments, voltage V(t) is an alternating voltage. Voltage source  68  may be operated by controller  54  and may be used to electrically charge handle  18  relative to an object  66  (e.g., a human hand or forearm) in the detection zone near handle  18  and/or relative to ground. The voltage V(t) of handle  18  may cause an electric field  64  to be generated outside handle  18 . 
     Electric field  64  may emanate from the entire surface of handle  18  (as shown in  FIG. 4 ) or from a particular portion of handle  18  (as shown in  FIG. 5 ). In some embodiments, handle  18  includes a shield  70  configured to block electric field  64 . For example,  FIG. 5  illustrates an embodiment of handle  18  in which shield  70  covers most of handle  18  and electric field  64  emanates only from an unshielded portion  72  of handle  18 . Shield  70  can be used to control the direction of electric field  64  such that electric field  64  is emanated only toward the detection zone. 
     Referring specifically to  FIGS. 6-8 , several cross sections of handle  18  are shown, according to an exemplary embodiment. In some embodiments, handle  18  has an electrically-conductive core  74  surrounded by an electrical insulator  76 . Voltage V(t) may be applied to core  74  by voltage source  68 . Insulator  76  may form an outer shell around core  74  to protect core  74  from damage and/or to prevent charge from escaping from core  74 . In other embodiments, handle  18  is a solid metal handle with no insulating shell. 
     In some embodiments, handle  18  does not include a shield  70 . For example,  FIG. 6  illustrates a cross-section A-A of the handle  18  shown in  FIG. 4 . In  FIG. 6 , handle  18  does not include a shield  70  and electric field  64  emanates from core  74  in all directions. Conductors on all sides of handle  18  may form an electric field  64  with core  74   
     In other embodiments, handle  18  includes a shield  70  surrounding some or all of core  74  at various locations along handle  18 . For example,  FIGS. 7-8  illustrate cross-sections B-B and C-C of the handle  18  shown in  FIG. 5 .  FIG. 7  is a cross-section at a location B-B where shield  70  surrounds all of core  74 . Shield  70  may be electrically connected to a separate conductor having the same value V(t) as voltage source  68  such that shield  70  and core  74  are electrically isolated but maintained at the same voltage V(t). By maintaining shield  70  and core  74  at voltage V(t), no electric field exists between shield  70  and core  74 . As shown in  FIG. 7 , any conductor outside handle  18  will form a separate electric field  78  with shield  70  and not with core  74 . 
       FIG. 8  is a cross-section at a location C-C where shield  70  surrounds some, but not all of core  74 . Electric field  64  emanates from core  74  through unshielded portion  72 . The rest of handle  18  is shielded by shield  70  and emanates a separate electric field  78  from shield  70 . Advantageously, electric field  64  may be directed toward the detection zone to detect objects  66  only in the detection zone. Conductors in other locations will instead form an electric field  78  with shield  70  and will not affect the estimated capacitance between core  74  and the objects  66  in the detection zone. 
     Referring now to  FIG. 9 , a simplified circuit diagram  80  illustrating the capacitance sensing principle used by controller  54  to determine the distance d between handle  18  and an object  66  in the detection zone is shown, according to an exemplary embodiment. Object  66  may be, for example, a human hand or forearm reaching for handle  18 . Controller  54  may use projected capacitance to determine the distance d between handle  18  and object  66 . Handle  18  forms one half of a capacitor and object  66  forms the other half of the capacitor. The capacitance C of the capacitor is defined by equation 
               82   ⁢     (       i   .   e   .     ,       I   ⁡     (   t   )       =     C   ⁢       ⅆ     V   ⁡     (   t   )           ⅆ   t             )       ,     where   ⁢           ⁢       ⅆ     V   ⁡     (   t   )           ⅆ   t               
is the derivative of the voltage V(t) applied by voltage source  68  and I(t) is the electric current between voltage source  68  and handle  18 . Controller  54  may modulate voltage V(t) such that
 
               ⅆ     V   ⁡     (   t   )           ⅆ   t           
is known. Controller  54  may measure electric current I(t) and calculate capacitance C using equation  82  and the known values of
 
               ⅆ     V   ⁡     (   t   )           ⅆ   t           
and I(t).
 
     Once the capacitance value C is known, controller  54  may use equation 
             84   ⁢     (       i   .   e   .     ,     C   =         ɛ   0     ⁢   KA     d         )           
to calculate the distance d between handle  18  and object  66 , where ∈ 0  is the permittivity of free space, K is the dielectric constant of the material between handle  18  and object  66 , and A is the area of handle  18  and object  66 . It can be assumed that the sizes of handle  18  and object  66  are constant and therefore capacitance C is inversely proportional to distance
 
               d   ⁡     (       i   .   e   .     ,     C   ∝     1   d         )       .         
Controller  54  may interpret any change in capacitance C as a result of a change in the distance d between handle  18  and object  66 .
 
     Referring now to  FIG. 10 , a block diagram of controller  54  is shown, according to an exemplary embodiment. Controller  54  is shown to include a communications interface  85  and a processing circuit  86 . Communications interface  85  may include wired or wireless interfaces (e.g., jacks, antennas, transmitters, receivers, transceivers, wire terminals, etc.) for conducting data communications with various systems, devices, or networks. Communications interface  85  can include an Ethernet card and port for sending and receiving data via an Ethernet-based communications network. In another example, communications interface  85  includes a WiFi transceiver for communicating via a wireless communications network. Communications interface  85  may be configured to communicate via local area networks or wide area networks (e.g., the Internet, a building WAN, etc.) and may use a variety of communications protocols (e.g., BACnet, IP, point-to-point, etc.). 
     In some embodiments, controller  54  uses communications interface  85  to receive input from various sensors  99  of refrigeration circuit  50  (e.g., temperature sensors, humidity sensors, pressure sensors, enthalpy sensors, voltage sensors, proximity sensors, etc.). Sensors  99  may be disposed at any location relative to temperature-controlled display device  10  and/or refrigeration circuit  50 . For example, sensors  99  may be positioned along any of lines  56 - 62 , within temperature-controlled space  20 , integrated with door handle  18 , or otherwise positioned to measure any variable state or condition of temperature-controlled display device  10 . Controller  54  may use inputs from sensors  99  to determine appropriate control outputs for the operable components of refrigeration circuit  50 . 
     In some embodiments, controller  54  uses communications interface  85  to send control signals to various operable components of refrigeration circuit  50 . For example, controller  54  may send control signals to compressors  42 , fans  26 ,  46 , valves  44 , and/or other operable components of refrigeration circuit  50  (e.g., flow control valves, pressure regulation valves, etc.) to circulate a fluid refrigerant between heat exchangers  48  and cooling elements  24 . In some embodiments, controller  54  uses communications interface  85  to communicate with other components of display device  10  such as an anti-condensate heaters, a lighting element, a condensate dissipation system, and/or other auxiliary components of display device  10 . 
     Still referring to  FIG. 10 , processing circuit  86  is shown to include a processor  88  and memory  90 . Processor  88  may be a general purpose or specific purpose processor, an application specific integrated circuit (ASIC), one or more field programmable gate arrays (FPGAs), a group of processing components, or other suitable processing components. Processor  88  is configured to execute computer code or instructions stored in memory  90  or received from other computer readable media (e.g., CDROM, network storage, a remote server, etc.). 
     Memory  90  may include one or more devices (e.g., memory units, memory devices, storage devices, etc.) for storing data and/or computer code for completing and/or facilitating the various processes described in the present disclosure. Memory  90  may include random access memory (RAM), read-only memory (ROM), hard drive storage, temporary storage, non-volatile memory, flash memory, optical memory, or any other suitable memory for storing software objects and/or computer instructions. Memory  90  may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in the present disclosure. Memory  90  may be communicably connected to processor  88  via processing circuit  86  and may include computer code for executing (e.g., by processor  88 ) one or more processes described herein. 
     Still referring to  FIG. 10 , memory  90  is shown to include a capacitance sensing module  91 . Capacitance sensing module  91  may be configured to estimate a capacitance C between handle  18  and an object  66  in a detection zone near handle  18 . Object  66  may be, for example, a human hand or forearm reaching for handle  18 . 
     Capacitance sensing module  91  may use projected capacitance to estimate the capacitance C between handle  18  and object  66 . Using projected capacitance, handle  18  forms one half of a capacitor and object  66  forms the other half of the capacitor. The capacitance C of the capacitor is defined by the equation: 
               I   ⁡     (   t   )       =     C   ⁢           ⁢       ⅆ     V   ⁡     (   t   )           ⅆ   t               
(shown as equation  82  in  FIG. 9 ), where
 
               ⅆ     V   ⁡     (   t   )           ⅆ   t           
is the derivative of the voltage V(t) applied by voltage source  68  and I(t) is the electric current between voltage source  68  and handle  18 .
 
     Capacitance sensing module  91  may modulate voltage V(t) such that 
               ⅆ     V   ⁡     (   t   )           ⅆ   t           
is known. Capacitance sensing module  91  may measure electric current I(t) and calculate capacitance C using equation  82  and the known values of
 
               ⅆ     V   ⁡     (   t   )           ⅆ   t           
and I(t). Capacitance sensing module  91  may estimate capacitance C using the equation:
 
     
       
         
           
             C 
             = 
             
               
                 I 
                 ⁡ 
                 
                   ( 
                   t 
                   ) 
                 
               
               
                 
                   ⅆ 
                   
                     V 
                     ⁡ 
                     
                       ( 
                       t 
                       ) 
                     
                   
                 
                 
                   ⅆ 
                   t 
                 
               
             
           
         
       
     
     Still referring to  FIG. 10 , memory  90  is shown to include a distance calculation module  92 . Distance calculation module  92  may be configured to calculate the distance d between handle  18  and object  66 . Distance calculation module  92  may use the capacitance value C estimated by capacitance sensing module  91  to calculate distance d. For example, distance calculation module  92  may use the equation: 
             C   =         ɛ   0     ⁢   KA     d           
(shown as equation  84  in  FIG. 9 ), where ∈ 0  is the permittivity of free space, K is the dielectric constant of the material between handle  18  and object  66 , and A is the area of handle  18  and object  66 .
 
     In some embodiments, distance calculation module  92  simplifies equation  84  by assuming that the sizes of handle  18  and object  66  are constant. With this assumption, equation  84  reduces to the simplified equation: 
             C   ∝     1   d           
which expresses the inverse relationship between capacitance C and distance d (i.e., capacitance C is inversely proportional to distance d). Distance calculation module  92  may interpret any change in capacitance C as a result of a change in the distance d between handle  18  and object  66 .
 
     Still referring to  FIG. 10 , memory  90  is shown to include a mode selection module  93 . Mode selection module  93  may be configured to select an operating mode for temperature-controlled display device  10  and/or refrigeration circuit  50  based on the distance d calculated by distance calculation module  92 . In some embodiments, mode selection module  93  compares the calculated distance d with a threshold value. 
     If the calculated distance d is not less than the threshold value (i.e., d≧threshold), mode selection module  93  may select a normal refrigeration mode. In the normal refrigeration mode, controller  54  may operate temperature-controlled display device  10  to maintain conditions (e.g., temperature, humidity, air pressure, etc.) within temperature-controlled space  20  at a setpoint or within a setpoint range. Mode selection module  93  may select the normal refrigeration mode in response to a determination that a user is not within a threshold distance of handle  18  (i.e., d≧threshold) and therefore door  12  is not about to be opened. 
     If the calculated distance d is less than the threshold value (i.e., d&lt;threshold), mode selection module  93  may select a more aggressive anti-ingression mode. In the anti-ingression mode, controller  54  may operate temperature-controlled display device  10  may to prevent the ingression of ambient air into temperature-controlled space  20 . For example, controller  54  may increase the speed of fan  26  to form air curtain  36 , establish a pressure gradient within temperature-controlled space  20 , activate additional fans or cooling elements, and/or perform other control operations designed to maintain conditions within temperature-controlled space  20  when door  12  is opened. Mode selection module  93  may select the ant-ingression mode in response to a determination that a user is within a threshold distance of handle  18  (e.g., a user is reaching for handle  18 , d&lt;threshold) and therefore door  12  is about to be opened. 
     Mode selection module  93  is configured to transition from the normal refrigeration mode into the more aggressive anti-ingression mode using input from the proximity sensor integrated with handle  18 . Advantageously, using proximity-based input for mode selection allows mode selection module  93  to transition into the anti-ingression mode before door  12  is opened and before any physical contact is made with handle  18 . Mode selection module  93  can initiate the anti-ingression mode preemptively in anticipation of door  12  being opened such that air curtain  36  and/or other anti-ingression measures are fully implemented by the time door  12  is opened. This allows for the anti-ingression measures to be more effective and enhances the energy efficiency of temperature-controlled display device  10 . 
     Still referring to  FIG. 10 , memory  90  is shown to include a fan control module  94 , a valve control module  95 , a compressor control module  96 , a lighting control module  97 , and an auxiliary control module  98 . Control modules  94 - 98  may be configured to control various components of temperature-controlled display device  10 . Fan control module  94  may be configured to control fans  26  and  46 . Valve control module  95  may be configured to control expansion valves  44  and/or other valves (e.g., fluid control valves) of refrigeration circuit  50 . Compressor control module  96  may be configured to control compressors  42 . Lighting control module  97  may be configured to control interior or exterior lighting elements of display device  10 . Auxiliary control module  98  may be configured to control auxiliary components of display device  10  such as an anti-condensate heating element, a condensate dissipation system, a user interface, and/or other auxiliary components that may be present in various implementations. 
     Control modules  94 - 98  may communicate with operable components of temperature-controlled display device  10  via communications interface  85 . In some embodiments, control modules  94 - 98  are configured to identify the current operating mode of display device  10  determined by mode selection module  93 . Control modules  94 - 98  may adjust the control signals sent via communication interface  85  based on the current operating mode. For example, fan control module  94  may increase the speed of fans  26  and/or  46  in response to a determination that the current operating mode has changed from the normal refrigeration mode to the more aggressive anti-ingression mode. In some embodiments, lighting control module  97  turns on/off or adjusts a brightness of a controlled lighting element upon a transition between operating modes. 
     Advantageously, control modules  94 - 98  may send control signals instructing various operable components of temperature-controlled display device  10  to change operating modes before door  12  is physically opened or touched. For example, control modules  94 - 98  may implement anti-ingression measures preemptively in anticipation of door  12  being opened. Such a preemptive implementation allows air curtain  36  and/or other anti-ingression measures to be fully implemented by the time door  12  is opened, thereby increasing the effectiveness of the anti-ingression measures and enhancing the energy efficiency of temperature-controlled display device  10 . 
     Referring now to  FIG. 11 , a flowchart of a process  200  for operating a temperature-controlled display device is shown, according to an exemplary embodiment. Process  200  may be performed by controller  54  as described with reference to  FIGS. 1-10 . Using process  200 , controller  54  may transition between multiple operating modes (e.g., a normal refrigeration mode, an anti-ingression mode, etc.) based on an estimated distance d between a handle of the temperature-controlled display device and an object (e.g., a human hand or forearm) in a detection zone adjacent to the handle. Process  200  allows controller  54  to anticipate when a door of the temperature-controlled display device is about to be opened and to transition into a more aggressive anti-ingression mode before the door is opened. 
     Process  200  is shown to include operating a temperature-controlled display device in a normal refrigeration mode (step  202 ). In the normal refrigeration mode, the temperature-controlled display device may be operated to maintain conditions (e.g., temperature, humidity, air pressure, etc.) within a temperature-controlled space at a setpoint or within a setpoint range. Step  202  may include receiving signals from various sensors of the temperature-controlled display device (e.g., temperature sensors, humidity sensors, enthalpy sensors, valve position sensors, proximity sensors, etc.) to determine an appropriate control signal for operable components of the temperature-controlled display device (e.g., compressors, valves, fans, etc.). 
     In some embodiments, step  202  includes operating a fan of the temperature-controlled display device at a first speed. The first speed may be a relatively lower speed and may be sufficient to maintain conditions within the temperature-controlled space when a door of the temperature-controlled display device is closed. 
     Still referring to  FIG. 11 , process  200  is shown to include detecting an object within a detection zone adjacent to a handle of the temperature-controlled display device (step  204 ). Step  204  may include using a proximity sensor integrated with the handle to detect the presence of a user&#39;s hand or forearm in the detection zone. In various embodiments, the proximity sensor may be located inside the handle, attached to the handle, installed near the handle, or otherwise positioned to monitor the detection zone adjacent to the handle. The proximity sensor may be a capacitive sensor (e.g., projected capacitive, mutual capacitive, self-capacitive, etc.) or other type of sensor (e.g., optical, microwave, ultrasound, magnetic, photoelectric, inductive, Doppler effect, sonar, radar, Eddy-current, etc.) configured to detect the presence of an object in the detection zone. 
     Process  200  is shown to include estimating a distance d between the handle and the object using an input from the proximity sensor (step  206 ). In some embodiments, step  206  includes estimating a capacitance C between the handle and the object using projected capacitance principles. Using projected capacitance, the handle forms one half of a capacitor and the object forms the other half of the capacitor. The capacitance C of the capacitor is defined by the equation: 
               I   ⁡     (   t   )       =     C   ⁢       ⅆ     V   ⁡     (   t   )           ⅆ   t               
where
 
               ⅆ     V   ⁡     (   t   )           ⅆ   t           
is the derivative of the voltage V(t) applied to the handle and I(t) is the electric current between the voltage source and the handle.
 
     Step  206  may include modulating modulate voltage V(t) such that 
               ⅆ     V   ⁡     (   t   )           ⅆ   t           
is known and measuring the electric current I(t) between the voltage source and the handle. Step  206  may
 
include calculating capacitance C using the known values of
 
               ⅆ     V   ⁡     (   t   )           ⅆ   t           
and I(t) and the following equation:
 
     
       
         
           
             C 
             = 
             
               
                 I 
                 ⁡ 
                 
                   ( 
                   t 
                   ) 
                 
               
               
                 
                   ⅆ 
                   
                     V 
                     ⁡ 
                     
                       ( 
                       t 
                       ) 
                     
                   
                 
                 
                   ⅆ 
                   t 
                 
               
             
           
         
       
     
     In some embodiments, step  206  includes using the estimated capacitance value C to calculate distance d. For example, step  206  may include using the following equation to calculate distance d: 
             d   =         ɛ   0     ⁢   KA     C           
where ∈ 0  is the permittivity of free space, K is the dielectric constant of the material between the handle and the detected object, and A is the area of the handle and the detected object.
 
     Since the sizes of the handle and the detected object can be assumed to be constant, the preceding equation can be simplified to: 
             d   ∝     1   C           
which expresses the inverse relationship between capacitance C and distance d (i.e., distance d is inversely proportional to capacitance C). Step  206  may include interpreting any change in capacitance C as a result of a change in the distance d between the handle and the detected object.
 
     Still referring to  FIG. 11 , process  200  is shown to include comparing the distance d estimated in step  206  with a threshold value (step  208 ). The threshold value may be a threshold distance within which it can be assumed that the a user is reaching for the handle and therefore the door of the temperature-controlled display device is about to be opened. 
     If the estimated distance is not less than the threshold value (i.e., the result of step  208  is “no”), process  200  may return to step  202  during which the temperature-controlled display device is operated in the normal refrigeration mode. If the estimated distance is less than the threshold value (i.e., the result of step  208  is “yes”), process  200  may proceed to step  210 . 
     Still referring to  FIG. 11 , process  200  is shown to include operating the temperature-controlled display device in an anti-ingression mode (step  210 ). In the anti-ingression mode, the temperature-controlled display device may be operated to prevent the ingression of ambient air into the temperature-controlled space. For example, step  210  may include increasing the speed of one or more fans to form an air barrier (e.g., an air curtain) over an opening into the temperature-controlled space that will be uncovered when the door is moved into the open position. Step  210  may include establishing a pressure gradient within the temperature-controlled space, activating additional fans or cooling elements, and/or performing other control operations designed to maintain conditions within the temperature-controlled space when the door is opened. 
     In some embodiments, step  210  includes starting a timer. The timer defines a minimum duration for which the temperature-controlled display device will be operated in the anti-ingression mode. Process  200  is shown to include determining whether the timer is expired (step  212 ). If the timer has not yet expired (i.e., the result of step  212  is “no”), process  200  may return to step  210  and continue to operate in the anti-ingression mode. Returning to step  210  directly from step  212  may not reset the timer. Process  200  may remain in the anti-ingression mode until the timer has expired. 
     Once the timer has expired (i.e., the result of step  212  is “yes”), process  200  may return to step  206 . The distance d between the handle and the proximity sensor may be re-estimated in step  206  and compared with the threshold distance value in step  208 . If the re-estimated distance is still less than the threshold value (i.e., the result of step  208  is “yes”), process  200  may proceed to step  210  and may remain in the anti-ingression mode. Proceeding to step  210  from step  208  may restart the timer. If the re-estimated distance is not less than the threshold value (i.e., the result of step  208  is “no”), process  200  may return to step  202  during which the temperature-controlled display device is operated in the normal refrigeration mode. 
     In some embodiments, the temperature-controlled display device includes multiple doors (as shown in  FIG. 1 ). Each door may have its own corresponding handle and corresponding proximity sensor configured to detect an object in a detection region adjacent to the corresponding handle. A separate instance of process  200  may be performed for each door of the temperature-controlled display device. Multiple instances of process  200  may be performed concurrently and may share the same timer. If any of the instances of process  200  proceed to step  210  from step  208 , the timer may be reset and the temperature-controlled display device may remain in the anti-ingression mode until all instances of process  200  return to step  202 . In other words, detecting an object within the threshold distance of any of the proximity sensors may trigger a transition into the anti-ingression mode for the entire refrigeration circuit. 
     In other embodiments, each instance of process  200  is independent (e.g., no shared timers or mode transitions) and affects a separate portion of the temperature-controlled display device. For example, the temperature-controlled display device may include multiple fans, each fan configured to generate an air curtain over a different door opening. Each fan may be individually controlled (i.e., increased in speed) in response to a determination that the door corresponding to the fan is about to be opened. In this way, the fans can be controlled so that only the fans that are necessary to provide an air curtain over an open door (or a door that is about to be opened) are operated at the higher speed. The remaining fans can be maintained at a relatively lower speed to conserve energy. 
     Referring now to  FIGS. 12-14 , several circuit diagrams that may be used to implement the door handle proximity sensor of the present disclosure are shown, according to an exemplary embodiment. As shown in  FIG. 12 , a voltage (e.g., 12 V) may be applied to the door handle sensor. In some embodiments, the voltage is an alternating voltage. The capacitance of a capacitor formed by the door handle sensor can be determined by measuring the electric current between the voltage source and the door handle sensor. Other branches of the circuit facilitate this measurement or allow the current to be measured in terms of a voltage between other nodes of the circuit.  FIG. 13  illustrates an embodiment in which a micro circuit or microprocessor is used in place of the circuit elements shown in  FIG. 12 .  FIG. 14  illustrates another embodiment of a circuit that may be used to apply a voltage to the door handle sensor and to measure the capacitance of a capacitor formed by the door handle sensor. In each of  FIGS. 12-14 , capacitance may be measured using equation  82 , as described with reference to  FIG. 9 . 
     The construction and arrangement of the systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few implementations of the present disclosure have been described in detail, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. 
     Numerous specific details are described to provide a thorough understanding of the disclosure. However, in certain instances, well-known or conventional details are not described in order to avoid obscuring the description. References to “some embodiments,” “one embodiment,” “an exemplary embodiment,” and/or “various embodiments” in the present disclosure can be, but not necessarily are, references to the same embodiment and such references mean at least one of the embodiments. 
     Alternative language and synonyms may be used for anyone or more of the terms discussed herein. No special significance should be placed upon whether or not a term is elaborated or discussed herein. Synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only, and is not intended to further limit the scope and meaning of the disclosure or of any exemplified term. Likewise, the disclosure is not limited to various embodiments given in this specification. 
     The elements and assemblies may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures, and combinations. Further, elements shown as integrally formed may be constructed of multiple parts or elements. 
     As used herein, the word “exemplary” is used to mean serving as an example, instance or illustration. Any implementation or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations or designs. Rather, use of the word exemplary is intended to present concepts in a concrete manner. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the preferred and other exemplary implementations without departing from the scope of the appended claims. 
     As used herein, the terms “approximately,” “about,” “substantially,” and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims. 
     As used herein, the term “coupled” means the joining of two members directly or indirectly to one another. Such joining may be stationary in nature or moveable in nature and/or such joining may allow for the flow of fluids, electricity, electrical signals, or other types of signals or communication between the two members. Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature. 
     Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure. 
     The present disclosure contemplates methods, systems and program products on any machine-readable media for accomplishing various operations. The embodiments of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions. 
     Although the figures show a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.