Abstract:
The invention provides a dual thermometer system for the measurement and display of temperature data taken at two separate locations within an oven. In one aspect, the invention provides an elongated probe connected with a flexible electronic cable. The probe houses two temperature sensors—one for sensing internal food temperature, one for sensing inside oven air temperature. The sensors are space apart within the probe such that the one sensor can be positioned substantially within a food item and the other sensor can positioned substantially outside of the food item and within the oven. Signals from the sensors are relayed from the probe and through the cable; external electronics may attach to the cable to acquire the signals and display associated temperatures. In another aspect, signals from temperature sensors are relayed from the probe and through the cable to a first wireless termination. The first wireless termination wirelessly relays signals from the probe to a second wireless termination coupled to module electronics, to acquire the wireless signals and to display associated temperatures. In operation, the probe is inserted into food within an operating oven, such that one of the sensors senses food temperature and such that the other of the sensors senses oven air temperature; the cable extends from the probe and through the door of the oven; the module electronics may be attached to a convenient location in the kitchen, usually near to the oven, to display temperatures from the probe.

Description:
RELATED APPLICATIONS 
   This application claims priority to U.S. provisional application Ser. No. 60/304,276, filed Jul. 9, 2001, and is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   This invention relates generally to temperature measuring devices, and more particularly, to a thermometer system for taking temperature measurements at differing locations. 
   DESCRIPTION OF RELATED ART 
   The prior art is familiar with meat thermometers of the type that include a probe inserted into meat to determine internal cooking temperature. By way of example, the following patents, each incorporated herein by reference, exemplify various prior art meat thermometers: U.S. Pat. Nos. 6,230,649; 4,547,643; 4,475,024; 4,201,968; 4,122,322; 4,058,013; 3,991,615; and 3,975,720. 
   The prior art is also familiar with solid-state ovens that include controls for setting oven temperature, with basic clock timing and the like. For example, the following patents are incorporated herein by reference and provide useful background to such ovens: U.S. Pat. Nos. 4,054,778; 3,800,123; and 3,521,030. 
   There is a need for improved temperature control of ovens and cooking thermometers to improve safety and delivery of prepared food. Certain bacteria and disease-related anomalies may survive cooking within an oven of the prior art because a user cannot properly monitor food doneness. In conventional temperature probes, for example, one may measure meat temperature at a selected point, but fail to notice undercooked portions. Conversely, over-cooking can also occur because of inadequate temperature monitoring. The actual oven inside air temperature may be too high and can thus burn the outer layer of the cooking food; conversely, if the oven air temperature is too low, it may not cook the food to desired doneness within the original cooking time. Temperature control options associated with current solid-state ovens also do not address such food preparation issues: specifically, stated temperature readings do not adequately link to actual food doneness and temperature. 
   SUMMARY OF THE INVENTION 
   It is, accordingly, a feature of the invention to provide a thermometer that determines simultaneously the temperature of food placed within an oven and the oven air temperature. It is another feature of the present invention to provide the thermometer with sensors for measuring each of the food and oven air temperature. It is yet another feature of the present invention to provide a communications cable to transfer signals from the temperature sensors to electronics external to the oven for processing of the signals and display of temperature values. It is still another feature of the present invention to provide such a thermometer with timing and processing food doneness options for ensuring proper food preparation within the oven. It is still another feature of the present invention to provide such a thermometer that can quickly measure temperature values, is easy to operate, and particularly well suited for the proposed usages thereof. 
   In one aspect, the invention provides an elongated probe connected with a flexible electronic cable. The probe houses two temperature sensors—one for sensing internal food temperature, one for sensing inside oven air temperature. The sensors are spaced apart within the probe such that the one sensor can be positioned substantially within a food item and the other sensor can be positioned substantially outside of the food item and within the oven. Signals from the sensors are relayed from the probe and through the cable; external electronics may attach to the cable to acquire the signals and display associated temperatures. 
   In another aspect, the invention utilizes wireless transmission of sensor signals. The invention provides an elongated metal probe connected with a flexible electronic cable. The probe houses two temperature sensors—one for sensing internal food temperature, one for sensing inside oven air temperature. Signals from the sensors are relayed from the probe and through the cable to a first wireless termination. The first wireless termination wirelessly relays signals from the probe to a second wireless termination coupled to module electronics, to acquire the wireless signals and to display associated temperatures. 
   In operation, the probe is inserted into food within an operating oven, such that one of the sensors senses food temperature and such that the other of the sensors senses oven air temperature; the cable extends from the probe and through the door of the oven; the first wireless termination connects with the cable and resides external to the oven; the first wireless termination relays signals from the probe to the second wireless termination, coupled to the module electronics; the module electronics may be attached to a convenient location in the kitchen, usually near to the oven, to display temperatures from the probe. 
   The invention thus has certain advantages by accurately measuring food temperatures, and also quickly indicating actual oven inside air temperature. Specifically, with the invention, a user may monitor air and food internal temperatures during cooking to achieve the desired food doneness while avoiding over- or under-cooking of the food. 
   Other advantages and components of the invention are apparent from the following description taken in conjunction with the accompanying drawings, which constitute a part of this specification and wherein are set forth exemplary aspects of the present invention to illustrate various features thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic drawing of the dual thermometer system according to an aspect of the present invention. 
       FIG. 2  is a schematic drawing of the dual thermometer system according to the aspect of  FIG. 1  showing the electrical connectivity of temperature sensors with the LCD module. 
       FIG. 3  is a cross sectional view of the present invention taken along line  3 — 3  showing the distal end of the probe. 
       FIG. 3A  is a cross sectional view of the present invention taken along line  3 A— 3 A showing the proximal end of the probe. 
       FIG. 4  is a cross-sectional view of the present invention taken along line  4 — 4  showing the communications cable. 
       FIG. 5  is a top plan view of the user interface according to an aspect of the present invention. 
       FIG. 6  is a schematic drawing of the dual thermometer system according to an aspect of the present invention showing the wireless termination. 
       FIG. 7  is a schematic drawing of the dual thermometer system according to an aspect of the present invention showing the related circuitry. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a dual thermometer system  10  (not to scale) constructed according to the invention. The system  10  includes an elongated probe  12 , an electronics communication cable  14 , and preferably, an LCD module  16  for displaying temperature data. The probe is preferably formed of stainless steel, and has a distal end  17  forming a tip  18  to facilitate piercing food  20  within an oven  22  (food  20  and oven  22  are shown without scale and only for purposes of illustration). Oven  22  is also illustratively shown with an oven door  22 A and oven housing  22 B. 
   Shown in more detail in  FIG. 2 , probe  12  has two temperature sensors illustratively located at locations  24 A,  24 B. These sensors are preferably thermistors. The temperature sensor at location  24 A is arranged within the distal end  17  of the probe at or near the tip  18  so as to sense temperature of food  20 ; the sensor at location  24 B is arranged within a proximal end forming a probe expansion section  26  to sense the temperature of oven air  28  within oven  22 . The sensors at locations  24 A,  24 B preferably operate in a temperature range of at least 32 to 572 degrees Fahrenheit, and also preferably have a physical separation of at least 100 mm, and ideally at least 120 mm, to ensure thermal decoupling for thermally independent measurements at each sensor. As shown in  FIG. 2 , these temperature sensors electronically couple to signal wires that communicate temperature signals from probe  12  and through cable  14 , so that LCD module  16  can capture and read the signals. 
   The distal end  17  of probe  12  preferably has a length D of approximately 120 mm. As shown in  FIG. 3 , the cross-sectional dimensions of the distal end  17  of probe  12  is typically between 4–5 mm. Probe expansion section  26  preferably has an elongated dimension F, of about 30 mm. As shown in  FIG. 3A , section  26  has a preferred cross-sectional dimension of between about 10–20 mm. Section  26  may be rectangular or oval in cross-sectional shape. These probe dimensions are chosen as to provide an adequately sized housing for positioning the sensors at locations  24 A,  24 B therein, and also to ensure that each of the sensors may take accurate temperature measurements independent of one another. 
   Cable  14  connected to section  26  has a length extending to LCD module  16  of about one meter. As shown in  FIG. 4 , cable  14  has a preferred cross-sectional dimension of 3.2 mm×2 mm; the thinner dimension G facilitates fitting cable  14  between oven door  22 A and housing  22 B as the cable is extended out of the oven  22 , as shown in  FIG. 1 . Cable  14  may also have a plug  29 , such as a stereo jack, at an end thereof opposite of probe  12  to facilitate connection to LCD module. 
   LCD module  16  includes a processor  30  to perform calculations and control of system  10 , including processing signals from the temperature sensors at locations  24 A,  24 B to show temperature information on a LCD display  32 . A user interface  34  provides for inputting user commands such as setting desired temperatures for both food  20  and oven  22 . Processor  30  preferably includes a timer, set by user inputs at user interface  34 , to monitor food doneness and oven temperatures relative to desired temperatures. Power for system operation is provided by battery  35  or other suitable power source. Module  16  may further include an alarm  36 , e.g., warning buzzer or LED, to warn the user of over- or under-cooking events. Additionally, module  16  may be configured to operate at up to about 140 degrees Fahrenheit such that the module can be placed in close proximity to the oven  22 . 
   Describing the user interface  34  in more detail, a number of input buttons  52  are preferably provided to increase the functionality of the system  10 , as shown in  FIG. 5 . Each of the input buttons  52  may perform one or more of the following functions: setting desired food and oven air temperatures, setting hour and minutes on a timer (count-up or count-down)—the duration being the total time or time elapsed at the desired food and/or oven air temperature, starting/stopping the timer, setting audio temperature alerts, toggling between Celsius and Fahrenheit temperature readings, toggling between temperature and timer displays, and turning system power on/off. For example, an input button  52  may be provided for setting one of the desired food and/or oven temperatures. Once these temperature values are reached, as measured by the sensors at locations  24   a ,  24   b , the alarm  36  will sound and the LCD display  32  will flash on and off at a specific duration of time the actual temperature measured such that the user is notified of the current cooking situation. If the hour and minute timer is set through the input buttons  52 , the alarm sounds and the LCD flashing display can also activate at the elapse of a timed event, and with various sounds and modes of flashing to distinguish from the temperature warnings. Further, the LCD display  32  may be configured to simultaneously display the desired and measured food and/or oven air temperatures, or the desired food and/or oven air temperatures and the timer. 
     FIG. 2  shows the detailed schematic layout of probe  12 , cable  14  and LCD module  16 . The temperature sensor  40 A is shown at distal end  12   a  of probe  12 ; and temperature sensor  40 B is shown at proximal end  12   b  of probe  12 . Sensors  40 A,  40 B connect with communication wires  50 A,  50 B, respectively, to communicate temperature signals to LCD module processor  30 . As a matter of design choice, processor  30  has an A/D converter  31  to convert the signals received from the sensors  40 A,  40 B to digital data. Processor  30  then converts these signals to temperatures for display on LCD display  32 . Data shown on display  32  is programmed at user interface  34 , as described herein. 
     FIG. 6  shows another aspect of an oven and food thermometer timer system  100  (not to scale) employing wireless terminations. System  100  includes an elongated probe  112 , an electronics communication cable  114 , a first wireless termination  115 A, a second wireless termination  115 B, and a LCD module  116 . First wireless termination  115 A wirelessly relays signals from probe  112  to second wireless termination  115 B coupled to LCD module  116 , to acquire the wireless signals and to display associated temperatures. 
   Probe  112  and cable  114  operate much like probe  12  and cable  14  of  FIG. 1 , with like dimensions and construction, such as shown in  FIGS. 2–4 . The probe  112  is preferably formed of stainless steel, and has a distal forming a tip  118  to facilitate piercing food  20  within an oven  22 . As in  FIG. 1 , oven  22  is illustratively shown with an oven door  22 A and oven housing  22 B. 
   Probe  112  has two temperature sensors illustratively located at points  124 A,  124 B. These sensors are preferably thermistors as described for the aspect of the invention shown in  FIG. 1 . The temperature sensor at location  124 A is arranged within the distal end of the probe  112  at or near the tip  118  so as to sense temperature of food  20 ; the sensor at location  124 B is arranged within a proximal end forming a probe expansion section  126  to sense the temperature of oven air  28  within oven  22 . The sensors  124 A,  124 B preferably have a physical separation of at least 100 mm, and ideally at least 120 mm, to ensure thermal decoupling for thermally independent measurements at each sensor. 
   Cable  114  connected to wireless termination  115 A has a length extending to termination  115 A of about one meter. Wireless termination  115 A relays signals from probe  112  as wireless signals  113  to wireless termination  115 B. Wireless termination  115 B may be within LCD module  116 , as shown, or external to module  116 , as a matter of design choice. 
     FIG. 6  shows the LCD module  116  with the same features as the aspect of the invention shown in  FIG. 1 , with the addition of the wireless termination  115 B such that sensor measurements are transmitted wirelessly to the LCD module. The LCD module  116  includes a processor  130  to perform calculations and control of system  100 , including processing signals from the temperature sensors at locations  124 A,  124 B to show temperature information on a LCD display  132 . A user interface  134  provides for inputting user commands such as setting desired temperatures for both food  20  and oven  22 . Processor  120  preferably includes a timer, set by user inputs at user interface  134 , to monitor food doneness and oven temperatures relative to desired temperatures. Module  116  may further include an alarm  136 , e.g., warning buzzer or LED, to warn the user of over- or under-cooking events. Module  116  may further include features of module  16  shown in  FIG. 2 . In one preferred aspect, module  116  is formed as a pager such that a user of system  100  can carry the pager to receive warnings from alarm  136  as programmed through user interface  134 . 
   Wireless termination  115 A may employ a “pager like” RF transmitter, known in the art and capable of operating at up to about 140 degrees Fahrenheit. Termination  115 A positioned outside the oven  22  couples to cable  114  located substantially within the oven. Thus, the cable is preferably configured to withstand temperatures of up to about 570 degrees Fahrenheit. Preferably, termination  115 A transmits wireless data containing information from the probe&#39;s internal temperature sensors. Optionally, wireless termination  115 A includes a LCD display to show basic temperature information within oven  20  and from one or both of the internal temperature sensors. 
   In the preferred aspect of the invention: cables  14 ,  114  of  FIG. 1  and  FIG. 6  are made from TEFLON-insulted wire inside a metal cable; probes  12 ,  112  are made from 572 degree F high temperature resistant &amp; food-grade stainless steel; and the thermisters inside probes  12 ,  112  are separated by a distance of at least 100 mm to ensure precise, thermally-independent temperature measurements at two locations. The LCD module  16  of the aspect of the invention shown in  FIG. 1 , and the wireless termination  115 A and LCD module  116  of the aspect of the invention shown in  FIG. 6 , may optionally have magnets  117  for mounting such elements upon a metal surface such as the oven door  22 , or suction cups  119  for mounting upon a feature such as the oven door  22 , a kitchen cabinet, etc., for easy and convenient viewing of temperature and timer readings. 
     FIG. 7  shows a schematic circuit diagram suitable for use with the electronics of the systems  10 ,  100  to control user inputs, temperature measurements, processing of data, and presentation of processed temperature and time data to the user in the form of audible and visual data. The two temperature sensors U 4 , U 4   a  are represented as thermistors. Processor U 1  directs the activity of the thermistors U 4 , U 4   a  and related circuitry to take temperature readings. A/D converter  31  of  FIG. 2 . is preferably integrated into the processor Ul. The related circuitry, shown as the resistors circuits lrt, lrt( a ), lrs, and lrs( a ) and capacitors C 9 , C 5 , can be formed with the termistors in the probe  12  or located external to the oven in the LCD module  16 . In the aspect of the invention of  FIG. 5 , wireless terminations  115 A,  115 B are located between the temperature sensors U 4 , U 4   a  and the processor U 1 . 
   User input commands are received through user interface  34  shown at switch or input button K in  FIG. 7  and connected to processor U 1 . Preferably, there are a number of input buttons K corresponding to setting desired food and oven air temperatures, setting hour and minutes on a timer, starting/stopping the timer, setting audio temperature alerts, toggling between Celcius and Farenheit temperature readings, toggling between temperature and timer displays, and turning system power on/off, as shown in  FIG. 5 . 
   LCD display U 2  has a series of lighted segments for visually displaying temperature and timer information, and communicates with processor U 1  through a series of communication lines. Alarm Q 1  has a speaker for providing audible alerts relating to temperature or timer values (e.g. set food or oven temperature has been reached, count up or down timer has expired). Alternatively, such alerts could appear on the LCD display U 2  as flashing lighted segments, the frequency and duration of the flashing depending on what event has occurred. 
   Processor U 1  determines when temperature measurements should be taken, which is either at set time intervals or upon user initiation through the user interface shown in  FIG. 5  at switches  52 . To take a temperature reading, a series of capacitor discharge times through the thermistors U 4 , U 4   a  is for example determined. 
   The first thermistor U 4  receives a discharge of current from capacitor C 9 , which then travels through the resistors lrt (R 4  and R 11 ), and lrs (R 2 , R 3 , and R 12 ) shown in  FIG. 7 . Discharge times (T)rs and (T)rt are measured and stored in the processor U 1 . Then, capacitor C 9  is recharged and subsequently discharged through the first thermistor U 4  and resistors Irt and the discharge time (T)rt is again measured. Because the electrical resistance of termistor U 4  is proportional to the temperature at the sensor location, processor U 1  can convert the measured discharge times into a digital temperature reading of the first thermistor. This reading is then displayed on LCD display U 2  as the first temperature sensor reading. The above process is self repeating such that a user is constantly updated of the current temperature measured by the temperature sensors. If the temperature value exceeds the limit of what thermistors U 4 , U 4   a  can measure, the system will review previous discharge times stored by the processor U 1  and convert such times to a temperature reading. 
   The second thermistor U 4   a  operates in the same fashion, and simultaneously with, the first thermistor U 4 . The second thermistor U 4   a  receives a discharge of current from capacitor C 5 , which then travels through the resistors lrt (R 6  and R 9 ), and lrs (R 8 , R 13 , and R 14 ) shown in  FIG. 7 . The discharge times (T)rs and (T)rt are measured and stored in the processor U 1 . Then, the capacitor C 5  is recharged and subsequently discharged through the second thermistor U 4   a  and resistors lrt( a ) and the discharge time (T)rt is again measured. Like the first thermistor U 4 , the measured discharge times are then converted into a digital temperature reading of the second thermistor U 4   a . This reading is then displayed on the LCD display U 2  as the second temperature sensor reading alongside the first temperature sensor reading. 
   The invention thus attains the features set forth above, among those apparent from the preceding description. Since certain changes may be made in the above methods and systems without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing be interpreted as illustrative and not in a limiting sense. It is also to be understood that the following claims are to cover all generic and specific features of the invention described herein, and all statements of the scope of the invention which, as a matter of language, might be said to fall there between.