Abstract:
A monitor system to monitor a characteristic of a user is disclosed. A monitor system includes a sensor producing signals indicative of glucose characteristics within the user. The sensor has a connector with a plurality of contacts, at least two contacts being shorted by a fuse trace. The monitor system further includes an electronics package with a package housing. The package housing contains a battery, a package port interfaced with the connector to receive signals from the sensor, and a package processor to process the signals from the sensor. Further included in the monitor system is a fuse system controlled by the package processor that includes a fuse timer, wherein the fuse trace is destroyed after the fuse timer reaches a threshold value.

Description:
RELATED APPLICATION 
       [0001]    The present disclosure is a Divisional of U.S. patent application Ser. No. 14/244,132 filed on Apr. 3, 2014, the contents of which are herein incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to monitor systems and, in particular embodiments, to devices and methods for operation of a sensor to determine a characteristic of a body. 
       BACKGROUND OF THE INVENTION 
       [0003]    Over the years, bodily characteristics have been determined by obtaining a sample of bodily fluid. For example, diabetics often test for blood glucose levels. Traditional blood glucose determinations have utilized a painful finger prick using a lancet to withdraw a small blood sample. This results in discomfort from the lancet as it contacts nerves in the subcutaneous tissue. The pain of lancing and the cumulative discomfort from multiple needle pricks is a strong reason why patients fail to comply with a medical testing regimen used to determine a change in characteristic over a period of time. Although non-invasive systems have been proposed, or are in development, none to date have been commercialized that are effective and provide accurate results. In addition, all of these systems are designed to provide data at discrete points and do not provide continuous data to show the variations in the characteristic between testing times. 
         [0004]    A variety of implantable electrochemical sensors have been developed for detecting and/or quantifying specific agents or compositions in a patient&#39;s blood. For instance, glucose sensors have been developed for use in obtaining an indication of blood glucose levels in a diabetic patient. Such readings are useful in monitoring and/or adjusting a treatment regimen which typically includes the regular administration of insulin to the patient. Thus, blood glucose readings improve medical therapies with semi-automated medication infusion pumps of the external type, as generally described in U.S. Pat. Nos. 4,562,751; 4,678,408; and 4,685,903; or automated implantable medication infusion pumps, as generally described in U.S. Pat. No. 4,573,994, which are herein incorporated by reference. Typical thin film sensors are described in commonly assigned U.S. Pat. Nos. 5,390,671; 5,391,250; 5,482,473; and 5,586,553 which are incorporated by reference herein, also see U.S. Pat. No. 5,299,571. However, the monitors for these continuous sensors provide alarms, updates, trend information and require sophisticated hardware to allow the user to program the monitor, calibrate the sensor, enter data and view data in the monitor and to provide real-time feedback to the user. This sophisticated hardware makes it most practical for users that require continuous monitoring with feedback to maintain tight control over their conditions. In addition, these systems require the user to be trained in their use, even if to be worn for short periods of time to collect medical data which will be analyzed later by a doctor. 
         [0005]    Doctors often need continuous measurements of a body parameter over a period of time to make an accurate diagnosis of a condition. For instance, Holter monitor systems are used to measure the EKG of a patient&#39;s heart over a period of time to detect abnormalities in the heart beat of the patient. Abnormalities detected in this manner may detect heart disease that would otherwise go undetected. These tests, while very useful are limited to monitoring of bio-mechanical physical changes in the body, such as a heart beat, respiration rate, blood pressure or the like. 
         [0006]    Electrochemical sensors typically have a well-defined finite time of use. Contributing to the finite life is the consumption or reaction of chemical reagents that allow the sensor to detect the desired agents and compositions. Upon consumption of the sensor reagents it is possible to get spurious or inaccurate readings from a sensor. It is therefore undesirable and even potentially dangerous to use a sensor beyond its designed lifetime. Despite the known dangers, there are documented cases of sensors being used well beyond their design lifetime. In order to provide accurate data and optimized care, it would be beneficial to have a sensor capable of turning itself off after a specified design lifetime has elapsed. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    In one embodiment a monitor system to record a characteristic of a user is disclosed. The monitor system includes a sensor to produce signals indicative of a glucose characteristic measured in the user. The sensor includes a connector with a plurality of contacts where at least two of the contacts being shorted by a fuse trace. The system further includes an electronics package that includes a package housing that contains, a battery, a package port interfaced with the connector to receive signals from the sensor, and a package processor to process the signals from the sensor and store the processed signals in non-volatile memory. Further included in the package housing is a fuse system controlled by the package processor that includes a fuse timer. Wherein the fuse trace is destroyed after the fuse timer reaches a threshold value. 
         [0008]    In another embodiment a monitor system to transmit a real-time characteristic of a user is disclosed. The monitor system includes a sensor to produce signals indicative of a glucose characteristic measured in the user, the sensor having a connector with a plurality of contacts, at least two contacts being shorted by a fuse trace; and an electronics package that includes a package housing, a battery being contained within the package housing, a package port interfaced with the connector to receive the produced signals from the sensor, a package processor to process the produced signals from the sensor and transmit the processed signals via a transmitter, a fuse system controlled by the package processor that includes a fuse timer; wherein the fuse trace is destroyed after the fuse timer reaches a threshold value. 
         [0009]    Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, various features of embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    A detailed description of embodiments of the invention will be made with reference to the accompanying drawings, wherein like numerals designate corresponding parts in the several figures. 
           [0011]      FIG. 1  is an exemplary illustration of components of a monitor system, in accordance with embodiments of the present invention. 
           [0012]      FIGS. 2A-2C  are exemplary illustrations of placement of a sensor and installation of the electronics package onto the sensor, in accordance with embodiments of the present invention. 
           [0013]      FIG. 3  is an exemplary block diagram illustrating components within the electronics package, in accordance with one embodiment of the present invention. 
           [0014]      FIGS. 4A-4D  are exemplary views of the fuse circuit in accordance with embodiments of the present invention. 
           [0015]      FIG. 5A  is an exemplary illustration of package port that would receive the connector from the sensor, in accordance with one embodiment of the present invention. 
           [0016]      FIGS. 5B-5D  illustrate various embodiments of detail of the recorder port, in accordance with embodiments of the present invention. 
           [0017]      FIG. 6  is an exemplary flow chart illustrating operations to initiate a sensor with a fuse, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    As shown in the drawings for purposes of illustration, the invention is embodied as a component within a subcutaneous implantable analyte sensor set that provide continuous data of the sensor readings to a portable infusion system. In some embodiments the sensor data is recorded into memory integrated into an electronics package that also provides power and wireless communication capability to the sensor. In other embodiments the sensor transmits sensor readings to an infusion pump that can include memory to store the sensor readings. The recorded sensor readings or data can later be downloaded or transferred to a computing device to determine body characteristic data based on the data recording over the period of time. In embodiments of the present invention, the analyte sensor set and monitor system are for determining glucose levels in the blood and/or bodily fluids of the user without the use of, or necessity of, complicated monitoring systems that require user training and interaction. However, it will be recognized that further embodiments of the invention may be used to determine the levels of other analytes or agents, characteristics or compositions, such as hormones, cholesterol, medications concentrations, viral loads (e.g., HIV), or the like. In other embodiments, the monitor system may also include the capability to be programmed to record data at specified time intervals. The monitor system and analyte sensor are primarily adapted for use in subcutaneous human tissue. However, still further embodiments may be placed in other types of tissue, such as muscle, lymph, organ tissue, veins, arteries or the like, and used in animal tissue. The analyte sensors may be subcutaneous sensors, transcutaneous sensors, percutaneous sensors, sub-dermal sensors, skin surface sensors, or the like. Embodiments may measure and record sensor readings on an intermittent or continuous basis. 
         [0019]      FIG. 1  is an exemplary illustration of components within a monitor system  100 , in accordance with embodiments of the present invention. The sensor  102  is shown from an exemplary top view as if it has been inserted into a patient. In one embodiment the sensor  102  utilizes an electrode-type sensor while in alternative embodiments, the sensor  102  may use other types of sensors, such as chemical based, optical based or the like. In further alternate embodiments, the sensor  102  may be of a type that is used on the external surface of the skin or placed below the skin layer of the user or placed in the blood stream of the user. Other embodiments of a surface mounted sensor would utilize interstitial fluid harvested from the skin. 
         [0020]    In some embodiments, the sensor  102  is an assembly commonly known as a “sensor set” that includes, but it not limited to the connector  104 , sensor adhesive (not shown) covered by an adhesive backing  106 , an introducer needle (not shown in  FIG. 1 ), a sensing portion of the sensor to be placed in a body (not shown), and a mounting base  105 . In one embodiment the connector  104  is integrally injection molded from plastic with the mounting base  105 . The connector  104  further includes electrical contacts that interface with contacts on the sensor. On a side opposite that shown in  FIG. 1 , the adhesive is applied to the mounting base  105  and the adhesive backing  116  is further applied over the adhesive. 
         [0021]    An electronic package  108  is also included in the monitor system  100 . The electronics package  108  includes a package housing  109  with a package port  110 . The package port  110  is designed to couple with the electrical contact on the connector  104  thereby providing power and other electrical interfaces between the electronics package  108  and the sensor  102 . In one embodiment the electronics package further includes a power source, processor and transmitter within the package housing  109 . The power source provides power for the processor and transmitter and when coupled to the connector  104 , further powers the sensor  102 . In such an embodiment signals generated by an installed sensor can be processed via the processor and transmitted to another device such as, but not limited to infusion pump  112 . In other embodiments, the electronics package  108  includes at least a power source, processor, transmitter along with memory and a receiver. In these embodiments sensor signals from an installed sensor can be stored to memory within the package housing  109  and periodically transmitted to the infusion pump  112  or other devices configured to communicate with the electronics package  108 . Additionally, the inclusion of the receiver within the electronics package would enable two-way communication between other devices and the electronics package  108 . 
         [0022]    The inclusion of memory within the electronics package  108  can enable the combined electronics package  108  and sensor  102  to be used as a Holter-type recording device that can use the package port  110  to interface with either the sensor  102  or a docking station (not shown) that is further connected to a computer of tablet computing device. When used as a recording device the combined electronics package  108  and sensor  102  have the capability to record and store data as it is received from the sensor  102 . When the electronics package  108  is coupled to a docking station the data stored on the memory of the electronics package  108  can be transferred to networked or local data storage and analyzed using general computing processors such as desktops, laptops, notebooks, netbooks, tablets, or handheld computing devices such as, but not limited to smart phones and the like. To enable data transfer through the dock, the dock may further include a data transfer cable such as, but not limited to USB or Thunderbolt or Ethernet directly coupled to a computing device. 
         [0023]    The infusion pump  112  included in the monitor system  100  includes a tubing  120  that is in connected to a reservoir  118  within the infusion pump  112 . Other characteristics of the infusion pump include a display  114  and a user interface  116 . In some embodiments the display  114  is a touchscreen thereby making the display  114  an integrated component of the user interface  116 . The infusion pump  112  can further include a radio transmitter and receiver that enables wireless communication. In some embodiments the radio transmitter is a standard off the shelf BLUETOOTH radio that includes the BLUETOOTH LOW ENEGRY profile. In other embodiments a custom secure radio transmission system is used. The radio transmitter within the infusion pump  112  enables wireless transmission with the electronics package  108  thereby allowing sensor data to shown on the display  114 . 
         [0024]    Transmission of sensor data to the infusion pump  112  further enables real-time glucose monitoring which can further enable low-glucose suspend functionality. In these embodiments if the sensor data indicates a blood sugar level below a specified threshold, the infusion pump  112  can suspend delivery of basal insulin. In some embodiments the raw sensor data measured by the sensor  102  is manipulated or processed using the processor within the electronics package  108  to determine sensor data from interstitial fluid that corresponds to a blood glucose level. In still other embodiments, the electronics package  108  transmits the raw sensor data to the insulin pump  112  where the raw sensor data is processed to correspond to a blood glucose level. In still other embodiments, the electronics package  108  transmits both the raw sensor data and a first calculated blood glucose level to the insulin pump. In these embodiments the insulin pump can then use a different algorithm to calculate a second blood glucose level from the raw sensor data. The second blood glucose level then being used in conjunction with the first blood glucose level to determine a third calculated blood glucose level. 
         [0025]    Further description regarding the sensor and associated sensor set can be found in U.S. Pat. No. 6,248,067, entitled A NALYTE SENSOR AND HOLTER-TYPE MONITOR SYSTEM AND METHOD OF USING THE SAME,  U.S. Pat. No. 5,586,553, entitled T RANSCUTANEOUS SENSOR INSERTION SET,  and U.S. Pat. No. 5,594,643, entitled D ISPOSABLE SENSOR INSERTION ASSEMBLY,  all of which is herein incorporated by reference. 
         [0026]      FIGS. 2A-2C  are exemplary illustrations of placement of a sensor  102  and installation of the electronics package  108  onto the sensor  102 , in accordance with embodiments of the present invention.  FIG. 2A  illustrates a sequence of typical steps used to place the sensor  102  within interstitial fluid of a patient. The leftmost panel of  FIG. 2A  is illustrative of using an inserter  200  to assist in the installation or placement of the sensor  102 . Commonly, inserters  200  are customized to accommodate a specific type of sensor  102 . For additional information regarding inserter  200  please see U.S. patent application Ser. No. 10/314,653 filed on Dec. 9, 2002, entitled I NSERTION DEVICE FOR INSERTION SET AND METHOD OF USING THE SAME,  U.S. Pat. No. 6,607,509, entitled I NSERTION DEVICE FOR AN INSERTION SET AND METHOD OF USING THE SAME,  and U.S. Pat. No. 5,851,197 entitled I NJECTOR FOR A SUBCUTANEOUS INFUSION SET,  all of which are herein incorporated by reference. 
         [0027]    The middle panel of  FIG. 2A  is an illustration showing the removal of the adhesive backing  106  to expose an adhesive that enables adhesion of the sensor  102  to skin  202  of a patient. The rightmost panel of  FIG. 2A  is an illustration that depicts the removal of an introducer needle  204  that is used during the placement of the sensor  102 .  FIG. 2B  is an exemplary illustration showing the installation of the electronics package  108  onto the sensor  102 . Direction arrows D 2  indicate that the electronics package  108  is pushed onto the sensor  102  that was adhered to the patient, as shown in the middle panel of  FIG. 2A . In some embodiments, it is desirable to wait a predetermined period of time before installing the electronics package  108  onto the sensor  102 . For example, it may be advantageous to wait for up to 15 minutes for the sensor  102  to be properly hydrated or wetted by the patient&#39;s interstitial fluid before attaching the electronics package  108 . In other embodiments it may take longer or less time before is sensor is considered properly hydrated. Being able to detect if an installed sensor  102  is properly hydrated can be used by a practitioner to help determine if the sensor was properly installed into the interstitial fluid. In other embodiments there is no minimum time required before attaching the electronics package  108  to the sensor  102 . In still more embodiments, the sensor  102  need not be hydrated before the electronics package  108  is connected. And in additional embodiments, the electronics package  108  may be integrated with the sensor before the sensor is inserted into a user. Once the electronics package  108  is coupled with the sensor  102  some embodiments initialize the sensor based on algorithms stored in the electronics package. During the initialization process algorithms can determine if the sensor is properly hydrated and will most likely function as designed. In other embodiments initialization of the sensor is not required. 
         [0028]    As illustrated in  FIG. 2C , some embodiments of the electronics package  108  include a feedback indicator  206 . In one embodiment the feedback indicator  206  is a light emitting diode (LED) that can be seen through a translucent or semi-translucent housing. In other embodiments, different light elements can be used, such as, but not limited to incandescent lights, fluorescent lights, organic light emitting diodes (OLED) or the like. In still other embodiments, the feedback indicator  206  can be an audible tone or a vibration alarm similar to those in mobile phones. In embodiments with the feedback indicator  206 , the electronics package  108  can provide feedback regarding the hydration level of a connected sensor. For example, the recorder includes hardware and software that can determine if the sensor  102  is properly hydrated. The feedback indicator  206  can help a practitioner by narrowing the type of troubleshooting that needs to be performed. For example, the feedback indicator  206  can be programmed to flash a specific sequence or color to indicate that the sensor  102  is properly hydrated. Similarly, the feedback indicator  206  can be programmed to flash a different sequence or color to indicate that the sensor is not properly hydrated. In other embodiments, the feedback indicator  206  can further be programmed to flash a particular sequence or color that indicates to a practitioner that the electronics package  108  is not fully charged or even that data needs to be transferred from the electronics package  108  before additional data can be recorded. The examples provided are not intended to be exhaustive of conditions that can be reported by the feedback indicator  206 . The particular examples provided are intended to be exemplary and should not be construed as limiting the scope of the present invention. 
         [0029]      FIG. 3  is an exemplary block diagram illustrating components within the electronics package  108 , in accordance with one embodiment of the present invention. A power supply  212  connected to power management  218  is found within the package housing  109  of the electronics package  108 . In some embodiments the power supply  212  is a battery assembly that uses a rechargeable battery chemistry to provide power to the electronics package  108 . In one embodiment the power supply  212  is made up of lithium ion battery cells. However, it is understood that alternate battery chemistries may be used, such as nickel metal hydride, alkaline or the like. Similarly, various embodiments can use a single battery cell for a shorter life such as for a single-use disposable unit while other embodiments use multiple battery cells that enable longer and/or reusable/rechargeable units. 
         [0030]    In rechargeable embodiments the power management  218  includes circuitry and programming to allow recharging of the power supply  212  via the package port  110 . In some embodiments power management  218  also includes circuitry and programming that enables a low battery warning alarm. In some embodiments the power supply  212  is capable of enabling the electronics package  108  to measure and/or record data for six days with a factor of safety of one additional day. Additionally, after six or seven days of measuring or recording data, the power supply further enables operation of an integrated clock in the electronics package  108  for an additional seven days. Alternative embodiments may provide longer or shorter battery lifetimes, or include a power port or solar cells to permit recharging of the power supply  212 . 
         [0031]    The sensor  102  is connected via the connector  104  and the package port  110  to a signal conditioning circuit  202 , such as a potentiostat or the like, in the package housing  109  of the electronics package  108 . The signal conditioning circuit  202  is in turn connected to a current to frequency converter (I to F)  204 . The output of the current to frequency converter  204  is a digital frequency that varies as a function of the sensor signal produced by the sensor  102 . In alternative embodiments, other signals, such as voltage, or the like, may be converted to frequency. In one embodiment, the digital frequency is then counted by a digital counter  206 , and a value from the digital counter  206  is periodically read and stored with an indication of elapsed time, by a microprocessor  208 , into a non-volatile memory  210 . In other embodiments the value from the digital counter  206  is sent to transmitter  211  for transmission to, but not limited to, the infusion pump (not shown). In further embodiments the transmitter  211  additionally functions as a receiver thereby allowing two way communication between the electronics package  108  and the infusion pump. 
         [0032]    In some embodiments, the electronics package  108  provides power to drive the sensor  102  via the package port  110  and the connector  104 . Power from the electronics package  108  may also be used to speed initialization of the sensor  102 , when it is first placed under the skin. The use of an initialization procedure can result in a sensor  102  providing stabilized data in an hour or less compared to requiring several hours before stabilized data is acquired without using an initializing procedure. One exemplary initialization procedure uses a two step process. First, a high voltage (preferably between 1.0-1.2 volts—although other voltages may be used) is applied to the sensor  102  for one to two minutes (although different time periods may be used) to initiate stabilization of the sensor  102 . Then, a lower voltage (preferably between 0.5-0.6 volts—although other voltages may be used) is applied for the remainder of the initialization procedure (typically 58 minutes or less). The initialization procedure described above is exemplary and other initialization procedures using differing currents, voltages, currents and voltages, different numbers of steps, or the like, may be used. In all embodiments the microprocessor  208  is further coupled to a fuse circuit  214 . The fuse circuit  214  can be used to help limit the number of uses of the sensor thereby ensuring sensors are not used beyond their expected lifecycle. Use of a sensor beyond its expected lifecycle can lead to erroneous and unreliable readings that may compromise the efficacy of therapy. Additional details regarding the fuse circuit will be discussed below. 
         [0033]      FIGS. 4A-4D  are exemplary views of the fuse circuit  214  in accordance with embodiments of the present invention.  FIG. 4A  illustrates a basic circuit diagram with switch  404  that is controlled by the microprocessor  208 . The charging of capacitor  402  would likewise be controller by the microprocessor  208 . Upon closing the switch  404  the capacitor  402  would discharge with enough energy to break fuse  400 .  FIG. 4B  illustrates elements of the fuse circuit that are implemented on the connector  104  from  FIG. 1 . As illustrated, fuse  400  is made by narrowing material that also makes up sensor detection pads  406   a  and  406   b . The sensor detection pads  406   a  and  406   b  being shorted by fuse  400  serve as a switch that signals to the electronics package that a sensor is plugged in. In some embodiments, upon detecting the sensor, the electronics package initiates a timer for a first specified time. Once the first specified time has elapsed the capacitor  402  is charged and discharged into the shorted sensor detection pads  406   a  and  406   b  thereby breaking the fuse  400 . In some embodiments the sensor signals can continue until the sensor is disconnected or until a second specified time has elapsed. The breaking of the short between sensor detection pads  406   a  and  406   b  can ensure that the sensor is only used once as the microprocessor can perform a check for shorted sensor detection pads  406   a  and  406   b  upon initialization of a sensor. 
         [0034]      FIGS. 4C and 4D  are illustrations of a first side  408  and a second side  410  of the connector  104 , in accordance with an embodiment of the present invention. The first side  408  includes the previously discussed sensor detection pads  406   a  and  406   b  along with fuse  400 . Located between the sensor detection pads  406   a  and  406   b  is an electrical contact for a second working electrode  418 . On the second side  410  of the connector  104  are the contacts for a counter electrode  412 , a first working electrode  414  and a reference electrode  416 . The relative position of the contacts should not be construed as limiting as the various locations can vary depending on how traces are made on the sensor. 
         [0035]      FIG. 5A  is an exemplary illustration of package port  110  that would receive the connector  104  from the sensor, in accordance with one embodiment of the present invention. The embodiment shown in  FIG. 5A  is a 10-pin connector that enables communication with the contact pads discussed in  FIGS. 4A-4D  while also providing additional electrical contacts for power, transmitters and receivers. The particular embodiments discussed in detail below should not be construed as limiting. Other embodiments can use various port and pin configurations. In still other embodiments, additional or fewer electrical contacts may be implemented on both the package port and the connector to enable or disable various sensor features. As shown in  FIG. 5A  pins  506   a  and  506   b  are designed to interface with sensor detection pads  406   a  and  406   b . Likewise, second working electrode pin  518  interfaces with second working electrode contact  418 . Counter pin  512 , first working electrode pin  515  and reference pin  516  interface respectively with counter contact  412 , first working electrode contact  415  and reference contact  416 . Further included are ground pin  502 , charge pin  504 , transmitter pin  510  and receiver pine  516 . For single-use embodiments, the charge pin  504  can be omitted. 
         [0036]      FIGS. 5B-5D  illustrate various embodiments of detail  520  of the recorder port  110 , in accordance with embodiments of the present invention. Detail  520  shows top contacts  522  and bottom contacts  524  which together can simply be referred to as “electronics package contacts”. In the embodiment illustrated the electronics package contacts are mounted to a circuit board  526  to which the components described in  FIG. 3  are also mounted. The electronics package contacts can be board mounted springs, or simple contact pads, or any other variety of contact that creates a reliable electrical connection. 
         [0037]    The configuration illustrated is intended to be exemplary and should not be construed to be limiting. For example, in alternative embodiments shown in  FIG. 5C , rather than a single recorder port  110  ( FIG. 5A ), the sensor  104  could have two separate ports with the first port  550  providing access to top contacts  522  while the second port  552  provides access to bottom contacts  524 . Similarly, other embodiments could use two separate ports while placing the bottom contacts  524  on the same side of the circuit board  526  as the top contacts  522 , as shown in  FIG. 5D . 
         [0038]      FIG. 6  is an exemplary flow chart illustrating operations to initiate a sensor with a fuse, in accordance with an embodiment of the present invention. The flow chart begins with START operation  600  followed by operation  602  where the connector for the sensor is inserted into the package port. Operation  604  utilizes the microprocessor within the electronics package to verify a short between the sensor detection pads. Operation  606  initiates a first timer and operation  608  determines if the first timer has reached the predetermined elapsed time. In some embodiments, the first timer allows the sensor to be used for 138 hours. In other embodiments, shorter or longer periods may be used for the first timer depending on the chemistry and configuration of the sensor. 
         [0039]    Operation  610  charges and discharges the capacitor within the fuse circuit to break the fuse and open the short between the sensor detection pads. Operation  612  starts a second timer that is programmed to stop the sensor from functioning after a specific time has elapsed. In one embodiment, the second timer is set to run for six hours. Together with the initial 138 hours, this embodiment results in 144 hours, or six days of sensor use. In other embodiments, six days of sensor use may also be the total number of days of use but various times can be used for the first timer and second timer to ensure the sensor does not cease functioning while a user is asleep. Accordingly, the first time period may be shortened in order to increase the second time period while still having the sensor operate for six days. In some embodiments the first and second timers are countdown timers that count down from the predetermined elapsed time to zero. In other embodiments, the first and second timers count forward until the elapsed time is the same as the predetermined elapsed time. In still other embodiments the first timer is a countdown timer and the second timer counts forward or vice versa. Operation  614  notifies the user via messages displayed on the infusion pump that disconnecting the sensor will permanently terminate use of the sensor. In some embodiments operation  614  further displays the amount of time remaining until the sensor stops functioning on the display of the infusion pump. 
         [0040]    In still other embodiments, the feedback indicator on the electronics package may begin blinking or flashing upon activation of the second timer. In some embodiments the color of the flashing LED of the feedback indicator of the electronics package can change the longer the second timer is running. For example, upon initiation of the second time, the LED may flash a first color such as green. When about half the time of the second timer has elapsed, the LED switches to a second color such as yellow. Finally, when about a quarter of the time for the second timer remains, the LED switches to a third color such as, but not limited to, red. In addition to changes color, in other embodiments the LED feedback indicator on the electronics package can also flash at different rates depending on how much time of the second timer remains. Operation  616  terminates the sensor. In some embodiments the sensor may continue to operate, but signals from the sensor are not processed or transmitted to other devices. In other embodiments sensor functionality is terminated by disconnecting the power supply. Operation  618  ends the process. 
         [0041]    While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention. 
         [0042]    The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.