Abstract:
One embodiment of the invention is directed to a temperature monitor comprising a housing, a temperature sensor to provide temperature indications, wherein the temperature sensor is disposed inside the housing and exposed to an ambient temperature, circuitry within the housing for processing and storing the temperature indications, and a power supply within the housing and coupled to the circuitry. The power supply is adapted to provide a level of power to the circuitry sufficient for the operability of the circuitry at least at any ambient temperature between −40° C. and −80° C. Another embodiment of the invention is directed to a method comprising acts of exposing the interior of a housing to a temperature below −40° C., measuring the temperature in the interior of the housing, storing an indication of the temperature within the housing, and processing the indication of the temperature within the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 60/519,458, entitled “Dry Ice Sensor with Liquid Crystal Display,” filed on Nov. 12, 2003, which is herein incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates generally to methods and apparatus for temperature sensing and, more particularly, to methods and apparatus for sensing temperatures down to approximately −80° C. using a probeless sensor.  
       DISCUSSION OF THE RELATED ART  
       [0003]     For certain perishable and/or consumable products, it is often useful, and in some cases critical, to know the temperature conditions to which the product has been exposed. Many products typically are transported in some form of a “supply-chain” from the product manufacturer or source to a purchaser or end-user. During transportation in such a supply-chain, which may include several links and involve significant time periods (transport via land, sea and/or air, storage in one or more warehouses, etc.), products may be exposed to a wide variety of environmental conditions, some of which may cause degradation of, or damage to, the product.  
         [0004]     For various products intended for human use or consumption (e.g., foods and food-related products, beverages, medicines, cosmetics, etc.), it is particularly useful to know if a given product has been exposed to undesirable temperature conditions (e.g., an undesirably high or low temperature, an undesirable duration at a temperature outside of a particular temperature range, an undesirable degree of temperature cycles or fluctuations, etc.). Such exposures can result in significant health and/or safety consequences. In some cases, products that are exposed to undesirable temperature conditions may be deemed unsafe for human consumption/use. Thus, information relating to various exposure conditions may be especially important in connection with medicines and other health-related products.  
         [0005]     Certain products, such as reagents and pharmaceuticals require very cold temperatures during transit and storage, and accordingly may be packaged with dry ice to maintain the low temperature of the product. Conventional temperature sensing of products in a dry ice environment has been performed using a temperature monitor having an external probe. The probe is placed inside the packaging of the product to measure the temperature of the product.  
       SUMMARY OF THE INVENTION  
       [0006]     One embodiment of the invention is directed to a temperature monitor comprising a housing, a temperature sensor to provide temperature indications, wherein the temperature sensor is disposed inside the housing and exposed to an ambient temperature, circuitry within the housing for processing and storing the temperature indications, and a power supply within the housing and coupled to the circuitry. The power supply is adapted to provide a level of power to the circuitry sufficient for the operability of the circuitry at least at any ambient temperature between −40° C. and −80° C.  
         [0007]     Another embodiment of the invention is directed to a method comprising acts of exposing the interior of a housing to a temperature below −40° C., measuring the temperature in the interior of the housing, storing an indication of the temperature within the housing, and processing the indication of the temperature within the housing.  
         [0008]     A further embodiment of the invention is directed to a temperature monitor comprising a housing, a temperature sensor to provide temperature indications, and means, within the housing, for processing and storing the temperature indications, wherein said means is operable when exposed to a temperature of approximately −80° C.  
         [0009]     Another embodiment of the invention is directed to a device, comprising a probeless temperature monitor, wherein the monitor is operable down to at least −80° C.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIGS. 1A and 1B  are top and side views, respectively, of a temperature monitor according to an embodiment of the invention;  
         [0011]      FIG. 2  is a functional block diagram representation of a temperature monitor according to an embodiment of the invention;  
         [0012]      FIG. 3  is a schematic representation of an exemplary implementation of the power supply shown in  FIG. 2 ;  
         [0013]      FIG. 4  is a schematic representation of an exemplary implementation of circuitry that comprises the microcontroller and LCD display of  FIG. 2 ; and  
         [0014]      FIG. 5  is a schematic representation of an exemplary implementation of circuitry that comprises the temperature sensing circuitry, optical communications circuitry, user interface, and data memory of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION  
       [0015]     As discussed above, temperature sensing of products in a dry ice environment has conventionally been performed using a temperature monitor having an external probe placed inside the packaging of the product. However, temperature monitors with probes have a number of drawbacks. For example, one drawback associated with monitors with probes is that they may be mistaken for explosives when placed inside a package being transported. In particular, the wiring that is used to connect the probe to the body of the monitor may be mistaken for wiring of an explosive. Under the heightened standards imposed by the Transportation Security Administration (TSA), suspicious packages, such as those with loose wires, are reported to authorities. Another drawback of monitors with probes is that they require an opening to be created in the packaging of the product to allow the probe to be placed inside. Such tampering with the packaging of the product may be undesirable.  
         [0016]     In view of the foregoing, one embodiment of the invention is directed to a temperature monitor that is capable of measuring very low temperatures, such as those encountered in a package including dry ice, without a probe. Implementing a temperature monitor capable of measuring very low temperatures without a probe presents an number of challenges. For example, in conventional temperature monitors with probes that are adapted to operate at very low temperatures, the body of the monitor is isolated from the ambient temperature since only the probe needs to be exposed to the temperature being measured. Thus, the electronics within the body of the monitor operate under normal temperature conditions.  
         [0017]     However, in the embodiment of the invention wherein the temperature monitor is adapted to measure very low temperatures without a probe, the temperature is sensed within the body of the monitor. Thus, the interior of the body of the monitor, and hence the components within the monitor, must be exposed to the very low temperatures being measured. In certain temperatures ranges (e.g., below −40° C.), this may render conventional monitor components inoperable or unreliable. Accordingly, embodiments of the invention are directed to monitor components that are designed to be operable at very low temperatures (e.g., down to −80° C. or colder).  
         [0018]      FIGS. 1A and 1B  illustrate top and side views of a probeless monitor that is adapted to measure very low temperatures according to an embodiment of the invention. Monitor  1  includes a housing  3 , which may be formed of a rigid, molded acrylonitrile butadiene-styrene (ABS) material. Monitor  1  further includes a liquid crystal display (LCD)  5  and optical ports  7   a ,  7   b , which are visible through openings in the housing.  
         [0019]     Optical port  7   a  may receive optical signals, while optical port  7   b  may transmit optical signals. For example, optical port  7   a  may receive configuration data and/or commands transmitted from an optical port coupled to a personal computer, personal digital assistant (PDA), or other remote device. Optical port  7   b  may transmit measured or processed temperature data to an optical port of a personal computer, PDA, or other remote device. The temperature information may then be stored, viewed, and/or manipulated on the personal computer. The optical signals received and transmitted by optical ports  7   a  and  7   b , respectively, may be infrared signals, radio frequency (RF) signals, or a combination thereof. According to one example, optical port  7   a  is implemented using a phototransistor and optical port  7   b  is implemented using an infrared light-emitting diode (LED).  
         [0020]     Control buttons  9   a ,  9   b  are also provided on the front surface of housing  3 . In the example of  FIG. 1 , control button  9   a  is designated as a “start” button and control button  9   b  is designated as a “stop” button. The start button, when pressed initially, begins the temperature monitoring and data recording process. Information may also be displayed on LCD  5  when the start button is pressed initially. If the start button is pressed when the monitor is already turned on, it causes the information displayed on LCD  5  to change. Alternatively, if the first depression of the start button does not cause information to be displayed on LCD  5 , the second depression of the start button may cause information to be displayed on LCD  5  and subsequent depressions of the start button may cause the information displayed on LCD  5  to change. The stop button may terminate the temperature monitoring and data recording process. Pressing the start button after the stop button has been pressed may cause information to be displayed on LCD  5 , but not reinitiate temperature monitoring and data recording.  
         [0021]     LCD  5  displays information about the measured temperature data. Examples of data that may be displayed are: a high temperature measured; a low temperature measured; an average temperature measured; an indication of whether the temperature measured fell below, above, or outside of a particular range; and an indication of the time the temperature measured fell below, above, or outside of a particular range. The data may be displayed as alphanumeric characters  1 . Although a temperature is shown in  FIG. 1A , alphanumeric characters may alternatively represent a time (e.g., hours and minutes), a percentage, a state, or another quantity or quality. Data indicators  13  may be displayed to indicate the nature of the information represented by alphanumeric characters  11  (e.g., a high temperature, a low temperature, or a duration in hours and minutes). LCD  5  may also display one or more icons. For example, LCD  5  may display a stop icon  15  to indicate that button  9   b  has been pressed and/or an alarm icon  17  to indicate. e.g., that the temperature measured fell below, above, or outside of a particular range.  
         [0022]     An adhesive pad  19  may optionally be included on rear panel  21  of housing  3 . The adhesive pad  19  may be used to adhere monitor  1  to a product being monitored or the packaging thereof. However, it should be appreciated that the monitor  1  need not be located on the product or packaging, and may simply be near the product. Furthermore, adhesive pad  19  may be substituted for or supplemented with another mechanism to couple monitor  1  to a product being monitored or the packaging thereof. For example, glue, Velcro, one or more clips, one or more straps, buttons or snaps, or some other coupling mechanism may alternatively be used.  
         [0023]      FIG. 2  illustrates an example of the components of a temperature monitor according to an embodiment of the invention. The monitor  22  comprises a microcontroller  23 , which is coupled to a power supply  25 , an LCD display  27 , optical communications circuitry  29 , a data memory  31 , a user interface  33 , and temperature sensing circuitry  35 . Although not illustrated in  FIG. 2 , the monitor  22  may also include a housing such as the housing  3  shown in  FIG. 1 . Such a housing may at least partially enclose the components illustrated in  FIG. 2 .  
         [0024]     The temperature within the monitor  22 , which should substantially equilibrate to the ambient temperature of the monitor over a period of time, is measured by temperature sensing circuitry  35 . Temperature sensing circuitry  35  comprises a temperature sensor, such as a thermistor, to sense the temperature within the monitor  22 . If the temperature sensor provides an analog indication of temperature, temperature sensing circuitry  35  may include circuitry to convert the analog temperature signal to a digital temperature signal.  
         [0025]     Memory  31  stores the measured temperature data. Microcontroller  23  may perform functions on the measured temperature data to, for example, determine properties of the measured temperature data. Such properties may be a high temperature measured, a low temperature measured, or an average temperature measured. The temperature data may also be processed to determine whether the temperature measured fell below, above, or outside of a particular range and, if so, the duration of time for which the temperature measured fell below, above, or outside of a particular range. The processed temperature data may also be stored in memory  31 . In addition, memory  31  may also store calibration data for the monitor, such as the calibration data that may be received via optical communications circuitry  29 , described below. The configuration data may include, for example, the sample rate for the monitor and the thresholds (e.g., maximum temperature, minimum temperature) that trigger an alarm indication on the LCD display  27 .  
         [0026]     Processed or measured temperature data may be viewable on the monitor  22  itself or remotely. On the monitor, such data may be displayed on LCD display  27  in any of the manners described in connection with  FIG. 1A . Remotely, the data may be displayed on personal computer, PDA, or other remote device. Optical communications circuitry  29  may be used to transmit measured or processed temperature data to the remote device in any of the manners discussed in connection with  FIG. 1A . In addition, optical communications circuitry  29  may be used to receive configuration data from a remote device as discussed in connection with  FIG. 1A .  
         [0027]     User interface  33  may include “start” and “stop” buttons as discussed in connection with  FIGS. 1A  or  1 B, or another mechanism for communicating commands from a user to monitor  22 . For example, user interface  33  may comprise one or more dials, sliding switches, flip switches, and/or touch sensors. The user interface  33  may be used to control the state of the monitor (e.g., on or off), the information that is displayed on LCD display  27 , or another aspect of monitor  22 .  
         [0028]      FIGS. 3, 4 , and  5  illustrate an exemplary implementation of the monitor  22  illustrated functionally in  FIG. 2 . Specifically,  FIG. 3  illustrates the power supply  25  of monitor  22 .  FIG. 4  illustrates circuitry  53  that comprises microcontroller  23  and LCD display  27  of monitor  22 . Finally,  FIG. 5  illustrates circuitry  55  that comprises the temperature sensing circuitry  35 , optical communications circuitry  29 , user interface  33 , and data memory  31  of monitor  22 , each of which is coupled to microcontroller  23  of circuitry  53  shown in  FIG. 4 .  
         [0029]      FIG. 3  illustrates an exemplary implementation of power supply  25 , shown  FIG. 2 . Power supply  25  comprises a battery  37 , a voltage regulator  39 , and a capacitor  41 . The positive lead of battery  37  is coupled to voltage input  43  and enable input  45  of voltage regulator  39 . Voltage regulator  39  includes a voltage output  47  and ground output  49 . Capacitor  41  is connected, at one end, to voltage output  47  at a node  51  and, at the other end, to ground output  49 .  
         [0030]     The signal  52  at node  51  is supplied to portions of monitor  22  that require power (e.g., microcontroller  23 , data memory  31 , and optical communications circuitry  29 ). Thus, the voltage and current supplied by power supply  25  at node  51  should be sufficient to allow for reliable operation of monitor  22  at the temperatures at which the monitor is operable. At low temperatures, the chemical reactions of a battery slow, which reduces battery output. In particular, the available capacity of a battery (i.e., the amount of electrical charge the battery can hold) and the maximum current of a battery both drop at low temperatures. Such a drop could render a monitor inoperable. For example, if a power supply failed to provide sufficient power during acquisition of a temperature measurement by temperature sensing circuitry  35 , the measurement could be corrupted.  
         [0031]     According to one example, power supply  25  is designed to provide sufficient power (i.e., voltage and current) at temperatures below −40° C. For example, power supply  25  may be adapted to provide sufficient power at temperatures below −60° C., below −80° C., or at even lower temperatures. According to one example, the voltage supplied by power supply  25  is greater than or equal to 2.2 V. For example, the voltage supplied by power supply  25  may be approximately 2.8 V. The power supply  25  should be able to accommodate draws of approximately 8 mA at temperatures as low as −80° C. or colder. Certain current intensive processes such as transmitting information via optical communications circuitry  29  may require approximately 8 mA of current.  
         [0032]     According to one exemplary implementation, battery  37  is a Lithium-Thionyl Chloride battery that provides a 3.6 V output. Preferably, battery  37  has a high energy density and is printed circuit board (PCB) compatible. One suitable example is a battery having part number LTC-7PN-S5, manufactured by Eagle-Picher Technologies, LLC of Joplin, Mo. At certain temperatures (e.g., temperatures below −50° C.), battery  37  may not be able to reliably supply its specified output (e.g., 3.6 V). Accordingly, the output of battery  37  is input to voltage regulator  39 , which will provide a substantially constant voltage output.  
         [0033]     According to one exemplary implementation, voltage regulator  39  will supply a substantially constant voltage that is lower than the voltage of battery  37 . Thus, the voltage at voltage output  47  will be substantially constant, even as the voltage supplied by battery  37  fluctuates. According to one exemplary implementation of voltage regulator  39 , the voltage at voltage output  47  is approximately 2.8 V. However, it should be appreciated that the invention is not limited in this respect and that other voltages may be used. For example, the voltage at voltage output  47  may be approximately 2.5 V according to another implementation. One suitable example voltage regulator has part number ZXCL280H5, and is manufactured by Zetex, Inc. of Hauppauge, N.Y.  
         [0034]     Capacitor  41  is connected between voltage output  47  and ground output  49  of voltage regulator  39 . At low temperatures, battery  37  may be slow in responding to a current draw, such as the current drawn when optical communications circuitry  29  is activated. Accordingly, capacitor  41  is provided to act as a buffer for current drawn on battery  37 . Capacitor  41  will store a charge, and therefore will function as a small battery that can provide current. According to one exemplary implementation, capacitor  41  has a capacitance of 0.1 uF. Capacitor  41  may also function to reduce noise of the signal at voltage output  47 , which may be generated by voltage regulator  39 .  
         [0035]      FIG. 4  illustrates an exemplary implementation of microcontroller  23  and LCD display  27 , shown in  FIG. 2 . Microcontroller  23  may be any suitable microcontroller that is enabled to operate at very low temperatures. One suitable example is a microcontroller having part number ML63611A, manufactured by Oki Semiconductor of Sunnyvale, Calif. Circuitry is shown coupled to microcontroller  23 , and may support the functions of microcontroller. For example, crystal  56  may be used to supply a clock LCD display  27  is coupled to microcontroller via a plurality of electrical connections  57  that are used to activate respective portions of the display. LCD display  27  may incorporate any combination of the features described in connection with LCD display  5  of  FIG. 1 . According to one exemplary implementation, LCD display  27  uses a low temperature fluid. As shown in  FIG. 4 , microcontroller  23  is coupled to circuitry  55 . The details of circuitry  55  are illustrated in  FIG. 5 , described below.  
         [0036]      FIG. 5  illustrates an exemplary implementation of temperature sensing circuitry  35 , optical communications circuitry  29 , user interface  33 , and data memory  31 , shown in  FIG. 2 . Each of temperature sensing circuitry  35 , optical communications circuitry  29 , user interface  33 , and data memory  31  are coupled to microcontroller  23  of circuitry  53  ( FIG. 4 ). Temperature sensing circuitry  31  includes a thermistor  59 , which has a resistance that changes in response to temperature. A capacitor  61  is included in temperature sensing circuitry  31 , which is charged through thermistor  59 . The number of times capacitor  61  may be charged over a time period through thermistor  59  is determined and stored. This number is then compared to the number of times capacitor  61  may be charged over the same time period through a reference resistor. The ratio of the two numbers is compared with a lookup table to determine the temperature sensed by thermistor  59 .  
         [0037]     User interface  33  includes switches  63  and  65 , which may correspond with control buttons  9   a ,  9   b  in  FIG. 1A . Thus, switches  63  and  65  may be used to provide control signals to microcontroller  23  in any of the manners for providing signals discussed in connection with  FIG. 1A . Switches  63  and  65  may control the state of the monitor (e.g., on or off), the information that is displayed on LCD display  27 , and/or another aspect of monitor  22 . It should be appreciated that switches  63  and  65  are not limited to the configuration shown and described in  FIG. 1A  and may assume any of the configurations described herein for accepting user input or another suitable configuration.  
         [0038]     Optical communications circuitry  29  comprises a phototransistor  67  and an infrared LED  69 . Signal  52  provides power to optical communications circuitry  29 . Phototransistor  67  receives optical signals, while infrared LED  69  transmits optical signals. Phototransistor  67  and infrared LED  69  may respectively receive or transmit signals in any of the manners discussed in connection with the optical ports  7   a ,  7   b  of with  FIG. 1 . For example, phototransistor  67  may receive configuration data and/or commands transmitted from an optical port coupled to a personal computer, PDA, or other remote device. Infrared LED  69  may transmit measured or processed temperature data to an optical port of a personal computer, PDA, or other remote device. It should be appreciated that the configuration of optical communications circuitry  29  is merely exemplary and that other configurations are possible. For example, the communications circuitry may be unidirectional rather than bidirectional, or may use transmission mediums other than or in addition to those described. Such transmission mediums may use wires or be wireless.  
         [0039]     According to one exemplary implementation, data memory  31  comprises an electrically erasable programmable read only memory (EEPROM) that requires a supply voltage equal to or less than that generated by power supply  25  ( FIG. 3 ). One suitable example is an EEPROM having part number 24LC32A, manufactured by Microchip Technology Inc. of Chandler, Ariz. Memory  31  may store the measured and/or processed temperature data, for example. Signal  52  provides power to data memory  31 .  
         [0040]     Having described several embodiments of the invention in detail, various modifications and improvements will readily occur to those skilled in the art. Such modifications and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only, and is not intended as limiting. The invention is limited only as defined by the following claims and the equivalents thereto.