Abstract:
The system comprises one or more sensor devices, where each sensor device is capable of measuring a temperature at a known location of a body of a human or other animal. Each sensor transmits a temperature measurement value and sensor identification to a monitor device. The monitor device receives the temperature measurement value and sensor identification, and computes an adjusted temperature value based upon the position of the measuring sensor, body age, and time of day. The adjusted temperature value is tested for alarm conditions and displayed for use by a caretaker.

Description:
BACKGROUND OF INVENTION  
         [0001]    The invention relates generally to the field of healthcare monitoring, and more particularly to a system and method for wireless temperature monitoring of human or other animals in a home, clinical or institutional setting. It provides a capability of adjusting temperature readings depending upon a body age, a temperature sensor position on the body, and time of day.  
           [0002]    One of the most common methods of monitoring the condition of a human or other animal body is by monitoring the body temperature. This is particularly important when a body is suffering from an illness, and particularly febrile or fever producing infections. Mercury filled glass thermometers have historically been the standard for measuring body temperature. Using conventional thermometers, body temperature is most accurately measured by taking oral, tympanic (ear), axillary (armpit), or rectal temperature readings. Because of the potential health and safety risk resulting from the use of mercury filled glass thermometers and the reduction in the price of digital thermometers, consumers are increasingly turning to digital thermometers distributed by large drugstore chains and discount department stores for monitoring body temperature. Because of the large number of children under the age of five years and the growing aging population in the United States, there is a need for new temperature monitoring products that are medically accurate, safe, comfortable, easy to use, and operationally reliable.  
           [0003]    While the present invention is applicable to people of all ages, it is more likely to find application in monitoring body temperatures of children, elderly individuals and those suffering from an illness. Children under the age of five who are kept at home generally encounter at least six febrile infections a year. This number increases by about fifty percent if the child attends a daycare center and is exposed to other children. Even though this number decreases somewhat between the ages of five and sixteen years, it is still common to experience several episodes of febrile infections per year at age sixteen. Since young children are oftentimes unable to understand or communicate when they may urgently need assistance, parents and other caretakers must be vigilant to determine the need for medical evaluation or therapy for these children. This is especially true at night when parents are apt to be sleeping. Although excessive or rapidly increasing temperature of the body is a more common cause of health concern, it is oftentimes equally important to monitor low or rapidly decreasing body temperature to be in a position to take remedial action, especially in the case of elderly patients.  
           [0004]    Since caretakers may also be family members of the sick as well as professional caretakers, they may also require rest and schedule flexibility in order to handle the demands of the sick family member as well as other demands and responsibilities of home and work. This often requires that the family caretaker endure an interrupted nights sleep in order to monitor a sick family member&#39;s temperature on a regular basis throughout the night, even though the sick family member&#39;s temperature remains within a nominally acceptable range. This regimen of repeated temperature measurements may be further compounded by diurnal variations in a patient&#39;s temperature as well as temporary responses to fever-reducing drugs, even though the fever appears to have subsided. This requirement for repeated temperature measurements also disrupts the patient&#39;s sleep when using conventional or digital thermometers. The result may be missed temperature measurements and sleep deprivation for both the caretaker and patient.  
         SUMMARY OF INVENTION  
         [0005]    The present invention provides a method and system for monitoring body temperature that is medically accurate, safe, comfortable, easy to use, and operationally reliable. It provides not only a continuous monitoring of body temperature, it also provides for notifying a caretaker when adjustable temperature alarm limits are exceeded. This reduces the time required for monitoring temperature by professional caretakers and enables family caretakers to get an uninterrupted night&#39;s sleep, if temperature alarm limits are not exceeded. It also enables the patient to get an uninterrupted night&#39;s sleep if temperature alarm limits are not exceeded. Another medically important parameter to monitor is the rate of change of body temperature. Alarm limits may be set for notifying a caretaker when temperature rate of change exceeds the adjustable alarm limits. The system may be readily used in an institutional, clinical, or home setting, and may be used to monitor a single temperature sensor affixed to a body or a multitude of temperature sensors.  
           [0006]    The invention is a temperature monitoring system consisting of a small sensor, a transmitter, and a receiver. The sensor may be attached to various locations on a body. There are numerous methods of attaching the sensor in a position to sense body temperature, including placement in a pocket of an adhesive strip or in a pocket pouch sewn into the armpit area of a person&#39;s shirt or nightgown. An elasticized panel is sewn into the shoulder armpit area in a manner that would not restrict the wearer&#39;s freedom of movement but would exert steady and gentle pressure on the sensor to keep it against the body. The sensor may also be secured to an appendage or other body locations. The cloth between the sensor and the skin, if any, is thin and highly heat conductive so as to allow accurate temperature readings. The sensor can be removed from the garment for washing but is difficult for a child to remove due to the number and size of snaps on the pocket. The adhesive strip is intended for children who may be tempted to remove a probe or other sensor. The garment is intended for children who may be tempted to remove a sensor if an adhesive strip was used. A sub-cutaneous version of the sensor may also be positioned under the skin of a human or other animal.  
           [0007]    The system may provide alerts to a caretaker by computing two different body temperature parameters, absolute temperature alarm limits and temperature trend alarm limits. If the body temperature exceeds a specified maximum or falls below a specified minimum level, an alarm may be activated. If the body temperature changes at a specified rate or faster, the alarm will also be activated. Different audible alarm sounds may be used, depending on why the alarm was activated. The system may also include a low battery alarm. Alarms may also provide for an escalating audible volume.  
           [0008]    The monitor houses the means to either receive temperature readings from the sensor using unidirectional communications or actively seek readings from the sensor upon request or at certain time intervals, using bi-directional communications. The monitor is located in the vicinity of a caretaker and detects whether an alarm condition exists based upon the temperature readings it receives from the sensor. The monitor may be easily carried by a caretaker throughout the vicinity of one or more sensors and may house an LCD display that indicates sensor identification, adjusted temperature, temperature trend, and a temperature time stamp. The monitor may include a memory function so recent temperatures could be displayed, and an alarm that sounds under the conditions described above. A version of the monitor may also include an annunciator for announcing temperature values.  
           [0009]    The system comprises at least one monitor device and one or more temperature sensors that communicate with the monitor device using wireless technology. The monitor device is capable of displaying current temperature, and temperature trends in either Celsius or Fahrenheit degrees, as well as identifying the selected sensor and time of day. The method also allows for adjustment of measured temperature due to locating a temperature sensor on different parts of a body, the age of the body, and time of day. The monitor device provides a means for adjusting temperature alarm limits and sounding an alarm when the temperature alarm limits are exceeded.  
           [0010]    Using conventional thermometers, body temperature is most accurately measured by taking oral, tympanic (ear), axillary (armpit), or rectal temperature readings. This is because the temperature measured at these locations is closer to the core temperature of a person&#39;s body. Since it is not practical to locate a sensor at some of these locations for periods of up to twelve hours or more, more practical locations for sensor placement include arm, trunk, leg or forehead.  
           [0011]    Sensors may be positioned either cutaneously or sub-cutaneously. However, there are varying differences between temperatures measured at these locations and the core temperature of a person&#39;s body. Since these differences are predictable, the present invention may use sensor location, body age, and time of day to adjust the measured temperature from the sensor to an adjusted body core temperature, which is a more meaningful measure of body temperature for determining medical condition and diagnosing illnesses.  
           [0012]    A method having features of the present invention comprises a method for monitoring body temperature that comprises the steps of measuring one or more temperature values by sensors at known locations on one or more bodies, transmitting the measured temperature values and corresponding sensor identifications from the sensors to a monitoring device, receiving the measured temperature values and corresponding sensor identifications by the monitoring device, computing adjusted temperature values from the measured temperature values based on the age, time of day, and known body locations of the corresponding sensors, and displaying the adjusted temperature values for use by a caretaker. The step of measuring may further comprise measuring at predetermined time intervals, and the step of transmitting may further comprise transmitting at the predetermined time intervals. The step of measuring may further comprise measuring in response to requests received from the monitor, and the step of transmitting may further comprise transmitting in response to the requests received from the monitor. The method may further comprise the step of calculating estimated remaining battery life of each sensor and transmitting the estimated battery life from each sensor to the monitoring device. The method may further comprise the step of detecting sensor errors/status, setting sensor error/status flags, and transmitting the sensor error/status flags from each sensor to the monitoring device. The method may further comprise the step of activating a sensor status indicator. The method may further comprise the step of switching the sensor to a low power mode when not measuring and transmitting. The step of transmitting the measured temperature values may comprise transmitting the measured temperature values via a wireless communication link, and the step of receiving the measured temperature values may comprise receiving the measured temperature values via a wireless communication link. The step of transmitting the measured temperature values may comprise transmitting the measured temperature values via a wireless area network, and the step of receiving the measured temperature values may comprise receiving the measured temperature values via a wireless area network. The step of displaying the adjusted temperature values may comprise displaying the adjusted temperature values via a multi-line display. The step of displaying the adjusted temperature values may comprise displaying the adjusted temperature values on a remote host display. The method may further comprise the step of selecting a sensor identification for displaying adjusted temperature values using a programmable keypad. The method may further comprise the step of providing visual alarm indication. The method may further comprise the step of providing audible alarm indication. The method may further comprise the step of setting upper and lower alarm limit values. The method may further comprise the step of setting upper and lower trend alarm limit values. The method may further comprise the step of computing adjusted temperature values from the measured temperature values based on the age of the body and time of day. The method may further comprise the step of positioning the sensors at locations selected from the group consisting of cutaneous locations, sub-cutaneous locations, appendages, trunk, neck and head. The method may further comprise the step of annunciating a selected adjusted temperature by the monitoring device. The audible alarm indication may be a time escalating volume audible alarm indication. The method may further comprise the step of providing an audible and text message display for alerting a caretaker of off-normal conditions. The method may further comprise the steps of calculating a cyclic redundancy check value within the sensor devices for the data to be transmitted, transmitting the cyclic redundancy check value with the temperature values, receiving the cyclic redundancy check values by the monitor device, computing a cyclic redundancy check value within the monitor device for the received data, and comparing the received and computed cyclic redundancy check value for error detection.  
           [0013]    In an alternate embodiment of the present invention, a system for monitoring body temperature comprises sensor devices for measuring one or more temperature values at known locations on one or more bodies, the sensor devices for transmitting the measured temperature values and corresponding sensor identifications from the sensors to a monitoring device, a monitor device for receiving the measured temperature values and corresponding sensor identifications, the monitor device for computing adjusted temperature values from the measured temperature values based on the known body locations of the corresponding, and means for displaying the adjusted temperature values for use by a caretaker. The system may further comprise a wireless communication link for conducting the transmitted and received temperature values and sensor identifications between the sensor devices and the monitor device. The system may further comprise a wireless area network for conducting the transmitted and received temperature values and sensor identifications between the sensor devices and the monitor device. The system may further comprise a remote host application and a remote host display for displaying adjusted temperature values to a caretaker. The monitor device may comprise an antenna connected to a receiver for receiving wireless signals from sensor devices, the receiver connected to a processor and non-volatile storage for demodulating and formatting the wireless signals, a visual alarm indicator connected to the processor, an audible alarm indicator connected to the processor, a programmable keypad connected to the processor, a display connected to the processor, an external communication means connected to the processor, and a battery for powering the circuits in the monitor device. The system may further comprise a transmitter connected between the antenna and the processor and non-volatile storage for transmitting commands and data-to sensor devices. The battery may be replaced by a power supply connected to an alternating current power source. The system may further comprise a remote host application connected to the external communication means and a remote host display connected to the remote host application for displaying adjusted historical and current temperature values for use by caretakers. The system may further comprise a sensor registration table including an entry for each sensor assigned to the monitor, the sensor registration table comprising a sensor identification number, a unique sensor registration number assigned during sensor manufacture, a sensor position indicator, body age, and upper and lower alarm limits. Each sensor device may comprise an antenna connected to a transmitter for sending wireless signals to a monitor device, the transmitter connected to a processor for modulating data and generating wireless signals, a temperature sensor connected to the processor, a status indicator connected to the processor, and a battery for powering the circuits in the sensor device. The system may further comprise a receiver connected between the antenna and the processor for receiving commands and data from the monitor device. The system may further comprise the monitor device for computing adjusted temperature values from the measured temperature values based on the age of the body and time of day. The system may further comprise means for positioning the sensors at locations selected from the group consisting of cutaneous locations, sub-cutaneous locations, appendages, trunk, neck and head. The system may further comprise the monitor device for annunciating a selected adjusted temperature by the monitoring device. The system may further comprise an audible alarm indication provided by the monitor device that is a time escalating volume audible alarm indication. The system may further comprise an audible and text message display on the monitor device for alerting a caretaker to off-normal conditions.  
           [0014]    Another embodiment of the present invention is a system for monitoring body temperature, including one or more sensor devices and a monitor device, the monitor device comprising means for receiving a measured temperature and sensor identification over a wireless link, a processor for controlling operation of the monitor device, means for computing an adjusted temperature value from the measured temperature value using a known body location of the measuring sensor, and means for displaying the adjusted temperature value for use by caretakers. Each sensor device may comprise means for measuring temperature at a known location of a body, a processor for controlling operation of the sensor device, and means for transmitting the measured temperature value and sensor identification over a wireless communication link. The system may further comprise means for computing an adjusted temperature value from the measured temperature value using the age of the body and time of day. The sensor may be positioned at a cutaneous location. The sensor may be positioned at a sub-cutaneous location. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0015]    These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings wherein:  
         [0016]    [0016]FIG. 1 shows system diagrams of a single monitor communicating with a multiplicity of temperature sensors;  
         [0017]    [0017]FIG. 2 shows block diagrams of a monitor;  
         [0018]    [0018]FIG. 3 shows a flow diagram that depicts monitor operation;  
         [0019]    [0019]FIG. 4 shows a typical user interface for a stand-alone monitor;  
         [0020]    [0020]FIG. 5 shows a display definition for a stand-alone monitor;  
         [0021]    [0021]FIG. 6 shows an example of a remote host display;  
         [0022]    [0022]FIG. 7 shows a definition of a sensor registration table;  
         [0023]    [0023]FIG. 8 shows a definition of a sensor data table;  
         [0024]    [0024]FIG. 9 shows block diagrams of a sensor;  
         [0025]    [0025]FIG. 10 shows a flow diagram that depicts sensor operation; and  
         [0026]    [0026]FIG. 11 shows a definition of sensor transmission data. 
     
    
     DETAILED DESCRIPTION  
       [0027]    Turning now to FIG. 1, FIG. 1 shows diagrams in FIG. 1A  100 , FIG. 1B  130 , and FIG. 1C  160  of systems for sensing and monitoring the temperature at locations on a body that makes use of a wireless communication link. The embodiment system  100  of FIG. 1A depicts a single monitor  115  communicating directly with a multiplicity of sensors  105  via wireless communication links  110 . An alternative embodiment system  130  of FIG. 1B depicts the use of a wireless area network  145  for linking a monitor  150  with a multiplicity of sensors  135  via a wireless area network  145  using communication links  140 . The sensors  105 ,  135  are wireless devices that sense temperature at a specific location on an individual&#39;s body and transmit the temperature information. The monitor  115 ,  150  is a device that receives the transmitted temperature data from the sensors  105 ,  135  and processes the data for display to a caretaker. The communication links  110 ,  140  are capable of reliable communication over distances of several hundred feet within a home or institutional setting. FIG. 1C depicts an augmentation to the system of FIG. 1A  160 , with the addition of a remote host application  170  connected to the monitor  115 , and a remote host display  175  connected to the remote host application  170 . In this configuration  160 , the monitor  115  is typically configured without an internal display, and has the capability of interfacing to a variety of external devices via RS232 Serial, IrDA, USB, Parallel, Firewire or other compatible communication port types. This configuration  160  allows the monitor to be used in a clinical environment where the monitor is configured to observe numerous temperature sensors positioned on numerous bodies. A wide variety of processing and displays are available in this configuration  160 . The wireless communication links may comprise any one of many communication configurations, including a wireless local area network (LAN) or a wireless personal area network (PAN).  
         [0028]    Turning now to FIG. 2, FIG. 2A and FIG. 2B show block diagrams of monitor devices  200 ,  250  for receiving, formatting, analyzing, and displaying temperature measurements from multiple assigned temperature sensors via wireless communication links. The monitor device  200 ,  250  alerts a caregiver when certain predefined conditions are occurring, such as temperature rising or falling, temperature has exceeded a certain value, a sensor battery life is minimal, intermittent reception from a sensor, and reception errors. These conditions may be displayed, and when enabled, alert the caregiver with various audible tones. The monitor device  200 ,  250  operates in a polling mode of operation, as depicted in FIG. 3. These configurations  200 ,  250  depict a monitor in a stand-alone mode and containing a user-friendly interface, such as an LCD 2×20 character display and up/down, right/left keypad, which allows a caretaker means to display the time and temperature of the sensors associated with the monitor. The monitor shown in FIG. 2A  200  depicts a unidirectional receive only monitor communication configuration, and the monitor shown in FIG. 2B  250  depicts a bi-directional transmit/receive monitor communication configuration. FIG. 2A depicts a monitor  200  that is battery operated and receives, formats, analyzes, alerts and displays temperature information supplied by each temperature sensor assigned to the monitor that is time and date stamped. Although the monitor  200  shown in FIG. 2A is powered by a battery  226 , it may also receive power from a power supply, as shown in FIG. 2B, connected to an AC power source, typically 115/220 VAC, 50/60 Hz. In the receive only configuration of FIG. 2A, an antenna  210  connected to a receiver  212  receives formatted temperature data from multiple sensors via wireless communication links. The receiver  212  sends the formatted temperature data to a processor and non-volatile storage  222 . A keypad  216  is also connected to the processor  222  to enable a user to select a designated temperature sensor for displaying the temperature sensor data on a display  220  connected to the processor  222 . The monitor  200  also has a visual alarm indicator  214  and an audible alarm indicator  218  for alerting a caretaker when a settable alarm limit has been exceeded. An additional voice feature may be activated that allows the monitor to annunciate the temperature of the selected sensor over the audible alarm indicator  218 . This feature is a software Implementation within the processor  222 . The monitor may also have the capability of connecting to other devices for exchanging data through other standard communication means, such as IrDA communication, RS232 serial communication, parallel communication, USB, Firewire, etc.  224 .  
         [0029]    [0029]FIG. 2B differs from FIG. 2A in that the monitor  250  also has a transmitter  230  connected between the antenna  210  and the processor  222  for providing bi-directional wireless communication with multiple temperature sensors, and a power supply  228  connected to an AC power source for powering the circuits in the monitor  250 . To make use of the bi-directional capabilities of the monitor  250 , the associated sensors must also have bi-directional wireless communication capability. The bi-directional communication capability enables a monitor to send address, command and response messages to the temperature sensors. This capability may provide a more reliable communication format.  
         [0030]    Turning now to FIG. 3, FIG. 3 shows a flow diagram that depicts monitor operation  300 . The monitor is a device that receives, formats, analyzes and displays the information received from its assigned sensors. The monitor also has the capability of alerting a caretaker when designated predefined conditions occur, e.g., a temperature exceeding an alarm point. The monitor operates in a polling mode by sequentially reading temperature values received from temperature sensors. When a monitor is started  310  by applying power to the device, the monitor system is initialized  312 . A test is then made to see if data has been received  314  from a sensor. If data is received  314 , it is formatted and stored, and a new data flag is set  316 . The sensor position on a body, the age of the body, and the time of day may be then used to compute an adjusted temperature  320 . If data is not received  314 , or after a new data flag has been set  316  and adjusted temperature computed  320 , a test is made to determine if a remote host is connected to the monitor  324 . If there is a remote host connected to the monitor  324  and there is a data request from the remote host  326 , the requested data is formatted  332  and sent to the requestor host  336 . Control is then directed to the step of testing for bi-directional communication  328 . If there is a remote host connected to the monitor  324  and there is no data request from the remote host  326 , control is then directed to the step of testing for bi-directional communication  328 . If there is no remote host connected to the monitor  324 , a test is made to determine if there has been a keypad input  330 . If there has not been a keypad input  330 , control is then directed to the step of testing for bi-directional communication  328 . If there has been a keypad input  330 , the user key input is processed  334  and associated data is displayed  338 , and control is then directed to the step of testing for bi-directional communication  328 . A test is conducted to determine if the monitor is utilizing bi-directional communication  328 . If not, control is returned to the step of testing for the presence of received data  314 . If bi-directional communication is being utilized  328 , a test is made to determine if it is time to send a request to a sensor for data transfer  322 . If not, control is returned to the step of testing for the presence of received data  314 . If is determined that a new data reading from a sensor is required  322 , a transmit request is sent to an appropriate sensor  318  and control is returned to the step of testing for the presence of received data  314 .  
         [0031]    Turning to FIG. 4, FIG. 4 shows a typical user interface  400  for a stand-alone monitor. The typical monitor user interface  400  may comprise a display  410  of two rows  412 ,  414  of  20  characters each using LCD display devices. Depending upon the target environment, a larger display such as a 4×20 or QVGA display may be configured into the monitor device. The first row of characters  412  could display information pertaining to a selected sensor reading, and the second row of characters  414  may be used to display functions relating to the function keys  420 ,  422 ,  424 ,  426 . Although the display device is depicted as a 2×20 LCD character array, it may be any display device capable of displaying the required text and numbers.  
         [0032]    Turning to FIG. 5, FIG. 5 shows a typical display definition  500  for a stand-alone monitor. A first row  522  may contain a sensor identification number  510 , a Fahrenheit/Celsius indicator  512 , a current temperature reading from the selected sensor  514 , a temperature trend indication  516 , a temperature time stamp  518 , and an AM/PM indicator. A second row  524  may contain an indicator of the functions  530 ,  532 ,  534 ,  536  assigned to each of the four programmable function keys  540 ,  542 ,  544 ,  546  for providing a wide variety of functions for navigating displaying and setting conditions to be monitored.  
         [0033]    Turning to FIG. 6, FIG. 6 shows an example  600  of a remote host display. A remote host display ( 175  in FIG. 1C) connects to a remote host application ( 170  in FIG. 1C), which connects to a monitor ( 115  in FIG. 1C) for providing temperature data to the host application. The remote host display is controlled by the specific host application that may be provided for the environment in which it is being used, e.g., day care, nursery, neo-natal, etc. The example display shown in FIG. 6 depicts tabular information for several individuals  610 ,  612 ,  614 ,  616 . The tabular information for each individual shows a column indicating the position of sensors located on different parts of an individual&#39;s body  620 , a column showing actual temperature measurements  622  of the sensors, and a column showing temperature measurements adjusted for the position of the sensors, age of the body and time of day  624 . By selecting one of the individuals  610 , the host application creates graphs of selected temperatures  630  of the selected individual over a selected time period. The graphs shown in FIG. 6 shows temperature trends from a sensor located on the selected individual&#39;s chest  632 , from a sensor located on the selected individual&#39;s arm  634 , and from a sensor located on the selected individual&#39;s leg  636 .  
         [0034]    Turning to FIG. 7, FIG. 7 shows a definition of a sensor registration table entry. The sensor registration table is a dynamic table that contains specific information pertaining to a specific sensors assigned to a monitor. As each sensor is assigned, an entry is created in the table for that specific sensor. FIG. 7A identifies fields in sensor table entries, including ID#  710 , Unique ID  720 , Sensor Position  730 , Age  740 , Upper Limit  750 , and Lower Limit  760 . Each of these fields is identified, sized, and defined in FIG. 7B. The Sensor Position field  730  indicates which part of a body the sensor is associated with. Adjustment to the actual temperature reading may be applied, depending on the sensor location or area  730 . Adjustment to the actual temperature reading may also be applied, depending on the age of the body or time of day  740 . The Upper Limit field  750  and the Lower Limit field  760 , values set by caretakers, are limits that can be used to generate an alarm condition to notify a caretaker when a temperature has exceeded the predefined limit value. An alarm condition may also be a rate of change or trend of temperature that is indicated by the Upper Limit field  750  and the Lower Limit field  760 . The alarm condition may generate any combination of audible or visual alerts.  
         [0035]    Turning to FIG. 8, FIG. 8 shows a definition of a sensor data table entry. The sensor data table is a table used to archive sensor information as a monitor receives it. The table is circular in definition, in that once the last entry in the buffer has been used, the next location will be the first location in the table. The result is that old data from a particular sensor will be over-written by new data from that sensor. The sensor data table contains multiple entries for each sensor associated with a monitor. As sensor information is received from each sensor, the information received in the transmission is entered into the table. FIG. 8A identifies fields in the sensor data table, including End  810 , New Entry  820 , ID#  830 , Status  840 , Measured Temperature  850 , Adjusted Temperature  860 , Time  870 , and Date  880 . Each of these fields is identified, sized, and defined in FIG. 8B. FIG. 8C depicts a sensor data table. The sensor data table is a dynamic table that contains all the information received by each of the sensors  890  assigned to a monitor. It is variable in length and circular in nature. After the last entry (1,000 in the example of FIG. 8C) has been logged, the next information received from any of the three sensors will be written into entry #1 location.  
         [0036]    Turning to FIG. 9, FIG. 9 shows block diagrams of a sensor. FIG. 9A depicts a sensor that has unidirectional communication capabilities  900 , and FIG. 9B depicts a sensor that has bi-directional communication capabilities  950 . The sensor block diagram  950  of FIG. 9B is identical to that shown in FIG. 9A  900 , but with the addition of a receiver  930  connected between the antenna  920  and the processor  914 . The receiver  930  provides an additional capability of bi-directional communication to enables a sensor to receive address, command and response messages from a monitor. This capability may provide a more reliable communication format. The sensor  900 ,  950  is a self-contained battery operated wireless device that senses and transmits temperature to a monitor. The sensor  900 ,  950  contains all the necessary electronics and software to sense temperature, convert the sensed temperature data, format the data, and transmit the appropriate information. As shown in FIG. 9A, the sensor  900  comprises an antenna  920  connected to a transmitter  910  for transmitting information to a monitor. The transmitter  910  connects to a processor  914 , which reads data from a temperature detector  912 , and may activate a status LED  916 . A battery  918  is provided to power the sensor  900 . The sensor  900  may contain diagnostic programs running in the processor  914  for determining if the detector  912  is connected and for determining approximate remaining battery capacity. If a failure occurs that is detected by the diagnostic program, the LED  916  may be activated.  
         [0037]    Turning to FIG. 10, FIG. 10 shows a flow diagram that depicts sensor operation  1000 . The sensor operates as a polling device when activated. When a new battery is installed, or removed and reinstalled  1010 , the sensor will initialize  1020 . After initialization  1020 , if an ON/OFF switch is in an ON position  1012  and there is no receiver present  1026 , the sensor will start polling by reading the temperature detector  1030 . If the ON/OFF switch is in the OFF position  1018 , the sensor will enter a deep sleep mode  1024 . All stored information is lost when a battery is removed. If there is a receiver present  1026 , the sensor will set a receiver interrupt enable  1028  and initiate a polling operation by reading the temperature detector  1030 . Subsequently, when a receiver interrupt occurs  1014 , the sensor reads the receiver  1022  to identify a command and initiate a polling operation by reading the temperature detector  1030 . During normal operation, the sensor will always put itself into some type of sleep mode to conserve battery power. The level of sleep depends on the ON/OFF switch. In the OFF position  1018 , the sensor enters into a deep sleep mode  1024  whereby it only maintains its configuration parameters and enables interrupt capability. In the ON position, the sensor runs its polling loop, transmits information and then will enter into a predetermined sleep mode  1016 . After the predetermined amount of time, the sensor will awake  1016  and conduct polling operations. The polling loop generally follows a repetitive sequence. After the temperature detector is read  1030 , the sensor determines if a detector error has occurred  1034 . If a detector error has occurred  1034 , a detector error flag is set  1032  and the polling operation continues. If a detector error has not occurred  1034 , the polling operation continues by calculating an estimated remaining battery life  1036 , formatting a message to be transmitted  1038 , transmitting the message to a monitor  1040 , setting the system indicator  1042 , setting a sleep timer  1044  and entering a normal sleep mode  1046  for a predetermined period of time or until a receiver interrupt occurs  1014 . When the normal sleep timer has expired  1016  or a receiver interrupt occurs  1014 , the polling operation is again initiated by reading the temperature detector  1030 . The sensor will continue to transmit information until the ON/OFF switch is placed in the OFF position or the battery is removed.  
         [0038]    Turning to FIG. 11, FIG. 11 shows a definition of sensor transmission data. The sensor transmits data at a pre-determined interval. FIG. 11A identifies fields in a data transmission, including Sync  1110 , Preamble  1120 , ID  1130 , Temp  1140 , Flags  1150 , Batt  1160  and CRC  1170 . Each of these fields is identified, sized, and defined in FIG. 11B. The rate at which the sensor transmits information to the monitor may vary depending on the temperature sensing device used.  
         [0039]    Although the present invention has been described in detail with reference to certain preferred embodiments, it should be apparent that modifications and adaptations to those embodiments might occur to persons skilled in the art without departing from the spirit and scope of the present invention.