Abstract:
A system and a method for monitoring and inspecting food safety is disclosed. The system adopts insert and use concept that only requires an initial push on a button to begin its function. The system provides visual alert for different conditions if food products are in unsafe status. The system is pre-calibrated during manufacture without complicated or multi-step calibration or recalibration procedures during application. The system relies on modern surface-mount microprocessor technology that enables long-term calibration stability along with very low power consumption for extended battery life.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 12/651,692, filed on Jan. 4, 2010 which is a continuation of U.S. application Ser. No. 11/229,621, filed on Sep. 20, 2005, the entire disclosures of each are herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to temperature measurement and, more particularly, to food safety inspection. 
     BACKGROUND OF THE INVENTION 
     In food service industry, during the course of transferring products from either cold storage or normal cooking status to some designated place, food safety is a big concern. Regulatory authority and the food service industry have established that potentially hazardous food products maintained either below 40° F. or above 140° F. are generally safe from the growth of potentially dangerous bacteria. Thus, the temperature window roughly between 40° F. and 140° F. can be considered to be a danger zone. To ensure food safety, a simple and effective inspection method for monitoring food temperature and then alerting if food temperature is in a danger zone is desired. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide an easy-to-use food inspection device and method that ensures that potentially hazardous food products are in safe status. 
     Another object of the present invention is to provide a visual alert if the potentially hazardous food products are in unsafe status so that people are warned in time to adopt necessary measures to ensure food safety. 
     In accordance with one aspect of this invention, a system and method of inspecting potentially hazardous food products adopts a simple and straightforward insert and use concept that only requires an initial push on a button to begin its function. 
     In accordance with another aspect of this invention, a system and method of inspecting potentially hazardous food products provides different visual alerts for different conditions if the potentially hazardous food is in the danger zone. 
     In accordance with a further aspect of this invention, a system and method of inspecting potentially hazardous food products is pre-calibrated during manufacture using sensitive thermistor temperature sensors and thus can eliminate or reduce complicated or multi-step calibration or recalibration procedures during application. 
     In accordance with a yet further aspect of this invention, a system and method of inspecting potentially hazardous products relies on microprocessor technology that enables long-term calibration stability along with very low power consumption for extended battery life. 
     The above and other objects, features, and advantages of the present invention will be apparent in the following detailed description of the preferred embodiments of the present invention when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of one embodiment of a food safety inspection device according to the invention. 
         FIGS. 2(   a ) and  2 ( b ) are flowcharts illustrating a method for the operation of the food safety inspection device according to an embodiment of the invention. 
         FIG. 3  is a diagram of another embodiment of the food safety inspection device according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a diagram of one embodiment of a food safety inspection device  100  for ensuring that the potentially hazardous food products (referred to “foods” thereafter) are in safe condition, i.e., the food temperatures are either below a lower temperature threshold (e.g., about 40° F.) or above a higher temperature threshold (e.g., about 140° F.), and providing a visual alert if the foods are in unsafe status, i.e., the food temperatures fall between the lower temperature threshold (e.g., about 40° F.) and the higher temperature threshold (e.g., about 140° F.), according to the invention. 
     It should be understood that the range of 40° F. to 140° F. is exemplary only, and that the device can be configured to operate according to different ranges without departing from the spirit and the scope of the invention. For example, a range of 30° F. to 150° F., or any other range suitable to the application, could be used. 
     The food safety inspection device  100  includes a power source  110 , a temperature sensor  120 , a reset mechanism  130 , a warning mechanism ( 140 , or  150 , or  140  and  150 ), and a processor  160 . 
     The food safety inspection device  100  is powered by a power source  110 , which supplies power to electronic components of the device. The power source can be either a DC or an AC power supply. The DC power supply can be any suitable commercial batteries available on the market. 
     The temperature sensor  120  is used as a medium to physically touch the inspected food and thus sense the temperature of the food. Of course, the sensor could be applied to physically touch a container holding the food (a plat, a can, et.) in addition to or instead of physically touching the food. According to one approach, the temperature sensor consists of a sensor tip and a thermistor which is physically located in the sensor tip&#39;s sheath; the sensing tip is about  6  inches in length and made up of stainless steel. Any suitable device for sensing or measuring temperature could be used. 
     The reset mechanism  130  is used to reset the device so that a measurement can be initiated. According to one approach, the reset mechanism can be made as a pushable button. Any other suitable mechanism for resetting the device could be used, such as toggle switch, etc. 
     The warning mechanism ( 140 , or  150 , or  140  and  150 ) is used to provide a warning when the inspected food is in unsafe status. The warning mechanism can be either in audio or visual form, or both. The audio form can be any indicium which can give off an audio warning such as beeping. The visual form can be any visual indicium which can give off a visual warning (e.g., flashing) such as light emitting diodes and light bulbs, or other suitable device for providing a visual indicia. According to one approach, the device has one visual indicium which can flash a color when alerting. According to another approach, the device has two visual indicia, when alerting, one giving off a red flashing warning  140  corresponding to one condition and the other giving off a blue flashing warning  150  corresponding to another condition. 
     The processor  160  is used to process measured data corresponding to the temperature of the inspected food. According to one approach, the processor  160  determines whether the food temperature falls below the lower temperature threshold or exceeds the higher temperature threshold, determines whether the food temperature falls between the lower temperature threshold and the higher temperature threshold, determine whether the food temperature falls between the lower temperature threshold and the middle temperature setpoint, and determine whether the food temperature falls between the middle temperature setpoint and the higher temperature threshold. Preferably, the processor comprises a memory, internal registers, a clock, and outputs. According to one embodiment, ATTiny13 AVR microprocessor is adopted. Other types of processors or controller-type devices could easily be used. 
       FIG. 2(   a ) is a flowchart illustrating the operation of a food safety inspection device with an audio indicium or one visual indicium as its warning mechanism according to one embodiment of the invention.  FIG. 2(   b ) is a flowchart illustrating the operation of the food safety inspection device with two visual indicia as its warning mechanism according to another embodiment of the invention. The method of  FIGS. 2   a  and  2   b  is described in connection with  FIG. 1  in order to set forth the method in a concrete fashion easily understood by the person of ordinary skill. However, this articulation of the method is exemplary only, and the method could be implemented using structures different from that of  FIG. 1 . 
     The user of the device first connects or installs a power source before the device is ready to inspect food as set forth in step  210 . The user then places the temperature sensor of the device on or into the food so that the temperature sensor physically touches the inspected food as per step  220 . According to step  230 , a reset mechanism is pushed to initiate the device. According to one approach, if the device uses an audio indicium as its warning mechanism, the device then beeps to indicate that the device is measuring the temperature of the inspected food. According to another approach, if the device uses one visual indicium (or two visual indicia) as its warning mechanism, the visual indicium (or indicia) light(s) up for several seconds (e.g., about 2 seconds). 
     According to one embodiment (i.e., the device uses audio indicium), when the monitored food is cold (e.g., below about 40° F.). , such as meat just taken out from a refrigerator, if the food safety inspection device is applied, the audio indicium remains off, which means the monitored food is in safe status and no safety action needs to be undertaken, as per steps  240  and  250 . When the monitored food is hot (e.g., above 140° F.). , such as just-cooked soup, if the food safety inspection device is applied, the audio indicium remains off, which represents the monitored food is also in safe status and no safety action needs to be undertaken, as per steps  240  and  250 . 
     Similarly, according to another embodiment (i.e., the device uses one visual indicium [or two visual indicia]), when the monitored food is cold (e.g., below about 40° F.). , if the food safety inspection device is applied, the visual warning indicium (or indicia) remains off, as per steps  240  and  250 . When the monitored food is hot (e.g., above 140° F.). , if the food safety inspection device is applied, the visual warning indicium (indicia) remain off, as per steps  240  and  250 . 
     When initially cold food is removed from cold storage and exposed to a warmer environment for certain period of time, e.g., a salad container is taken out from a refrigerator and placed on a counter for later serving, the temperature of the food gradually increases. Once the temperature of the monitored food increases over a lower threshold (e.g., about 40° F.), the audio indicium or visual indicium (or indicia) gives off a warning. According to one approach (i.e., the device uses an audio indicium), the device starts to beep until the reset mechanism is pushed, which indicates that the monitored food is on unsafe condition, as per step  260 . According to another approach (i.e., the device has one visual indicium), the device starts to flash in a fast blinking mode until the reset mechanism is pushed, as per step  260 . According to one further approach (i.e., the device has two visual indicia), the red visual indicium starts to flash until the reset mechanism is pushed, as per steps  270  and  280 . 
     Likewise, when initially hot food is exposed to air for a while, e.g., a just-cooked soup, the temperature of the food gradually decreases. Once the temperature of the monitored food decreases below the higher temperature threshold (e.g., about 140° F.), the audio indicium or visual indicium (or indicia) gives off warning. According to one approach (i.e., the device uses an audio indicium), the device starts to beep until the reset mechanism is pushed, which indicates that the monitored food is on unsafe condition, as per step  260 . According to another approach (i.e., the device has one visual indicium), the device starts to flash until the reset mechanism is pushed, as per step  260 . According to one further approach (i.e., the device has two visual indicia), the blue visual indicium starts to flash until the reset mechanism is pushed, as per steps  270  and  290 . 
     If the temperature of the monitored food is around the middle of temperature range between the lower temperature threshold (e.g., about 40° F.) and the higher temperature threshold (e.g., about 140° F.). , according to one embodiment (i.e., the device uses two visual indicia), the red indicium flashes when the monitored food is below a roughly middle temperature setpoint (e.g., about 90° F.) as per step  280 , and the blue indicium will flash when the monitored food is above the roughly middle temperature setpoint (e.g. about 90° F.) as per step  290 . 
     The flash of the visual indicium can alert relevant personnel so that some action can be taken. For example, the temperature of the initially hot foods can be raised up above the higher temperature threshold (e.g., about 140° F.). , or the temperature of the initially cold foods can be lowered down below the lower temperature threshold (e.g., about 40° F.). Thus, the monitored foods can be monitored or returned to a safe condition. Of course, if the food is in unsafe status, the establishment can simply dispose of the food rather than returning it to a safe temperature. 
       FIG. 3  illustrates how a food safety inspection device measures the temperature of the inspected food according to an embodiment of the invention. 
     To initiate a measurement cycle, the output ports  170  and  180  are first driven low for a time period proportional to a time constant, where the time constant is the product of the thermistor  120  resistance, R, and capacitor&#39;s  310  capacitance, C. This allows enough time for the capacitor, C, to fully discharge. Then both output ports  170  and  180  are driven high, charging the capacitor through the thermistor&#39;s resistance. Once the capacitor becomes adequately charged, the transistor  320  turns on and pulls the output port  180  low. The time for the output port  180  to be driven from high to low by the transistor  250  is a function of R×C×Constant of the Circuit . Since the resistance, R, of the thermistor is related to temperature of the sensor, the time lapse is directly related to the temperature. The processor&#39;s internal clock is used to measure this time lapse. 
     By means of a calibration procedure during manufacture, the time lapses are calibrated to correspond to the designated temperatures, and programmed into the processor  160 . By matching the measured time lapse with the calibrated value stored in the processor  160 , the processor  160  can determine the actual temperature of the monitored food and thus whether the food is in safe or unsafe status. 
     According to one embodiment, the processor can transmit the temperature data to a remote receiver at a designated interval to keep a record of temperature history. The remote receiver could be any device which is able to receive, save, and display the transmitted data. The processor could transmit the data through a wired connection (e.g., cables) or through a wireless connection (e.g., RF transmitter, etc.). The data can be forwarded over a network (Internet, Intranet, etc.) to be monitored and further evaluated. 
     One variation of the present invention is that the food safety inspection device could be mounted on coolers. For example, when the cooler goes above 40° F., the device will flash a red light to alert people about the safety status of the foods in the cooler. Modification of the sensor  120  may be appropriate for this application so that the sensor can be easily attached to the inner wall of the cooler. The temperature sensor  120  can be detached from the other components of the device so that the sensor is located inside the cooler and the other components of the device are attached or located outside the cooler. 
     One further variation of the present invention is that the device is redesigned so that it can float in a bath tub when a mother prepares for bathing a baby. If the bath water is too hot (i.e., above some specific temperature), the device will flash and alert the mother so that the mother can adjust the bath temperature to ensure the comfort and safety of the baby. This embodiment could be implemented using the basic components of  FIG. 1 , and with the addition of some protective material to waterproof the device and provide for buoyancy. 
     A specific embodiment of the food safety inspection device according to the invention has been described for the purpose of illustrating the manner in which the invention may be made and used. It should be understood that implementation of other variations and modifications of the invention in its various aspects will be apparent to those skilled in the art and that the invention is not limited by the specific embodiment described. It is therefore contemplated to cover by the present invention any and all modifications, variations, or equivalents that fall within the true spirit and scope of the basic underlying principles disclosed and claimed herein.