Electronic time-temperature indicator and logger
First Claim
1. A unitized electronic time-temperature indicator device for rapidly assessing the acceptability of a material'"'"'s thermal history,said device containing computational means, and a temperature measurement means;
- wherein said device periodically samples the temperature and computes a function of temperature that is continually operative throughout the relevant temperature monitoring range of the device;
and wherein said function of temperature approximates the impact that the relevant temperature, for that period'"'"'s length of time, has on a detectable property of said material;
and wherein said computational means generate a running sum of said function of temperature over time;
and wherein said function of temperature resides with said unitized device;
and wherein the granularity of the function of temperature is small enough, and the frequency of time measurements is often enough, as to substantially approximate the impact of time and temperature on the detectable property of said material;
and in which said running sum is compared to a reference value, and the result of said comparison is used to generate an output signal indicative of the fitness for use of said material.
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Abstract
This invention covers improved electronic time-temperature indicators with a visual output, and other devices and methods by which the thermal history of a complex material, which may not obey a simple exponential Arrhenius law degradation equation, may be monitored, and the subsequent fitness for use of the tracked material may be quickly ascertained. In particular, the invention discloses a rapidly reprogrammable electronic time-temperature tag that may be easily customized with the thermal time-temperature stability profile of an arbitrary material, using electronic data transfer methods. Using this device, a single, low-cost, generic time-temperature tag may be mass-produced, and then subsequently programmed to mimic the stability characteristics of nearly any material of interest.
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Citations
25 Claims
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1. A unitized electronic time-temperature indicator device for rapidly assessing the acceptability of a material'"'"'s thermal history,
said device containing computational means, and a temperature measurement means; -
wherein said device periodically samples the temperature and computes a function of temperature that is continually operative throughout the relevant temperature monitoring range of the device; and wherein said function of temperature approximates the impact that the relevant temperature, for that period'"'"'s length of time, has on a detectable property of said material; and wherein said computational means generate a running sum of said function of temperature over time; and wherein said function of temperature resides with said unitized device; and wherein the granularity of the function of temperature is small enough, and the frequency of time measurements is often enough, as to substantially approximate the impact of time and temperature on the detectable property of said material; and in which said running sum is compared to a reference value, and the result of said comparison is used to generate an output signal indicative of the fitness for use of said material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A unitized electronic time-temperature indicator device for rapidly assessing the acceptability of a material'"'"'s thermal history,
said device containing computational means, and a temperature measurement means; -
wherein said device periodically samples the temperature and computes a function of temperature that is continually operative throughout the relevant temperature monitoring range of the device; and wherein said function of temperature is in the form of a multi-element lookup table or set of equation parameters that is capable of rendering complex temperature functions that cannot be adequately modeled by a single exponential Arrhenius equation; and wherein said function of temperature approximates the impact that the relevant temperature, for that period'"'"'s length of time, has on a detectable property of said material; and wherein said computational means generate a running sum of said function of temperature over time; and wherein said fraction of temperature resides with said unitized device; and wherein the granularity of the function of temperature is small enough, and the frequency of time measurements is often enough, as to substantially approximate the impact of time and temperature on the detectable property of said material; and in which said running sum is compared to a reference value, and the result of said comparison is used to generate a visual output indicative of the fitness for use of said material, and the device contains means to allow the function of temperature and reference value to be automatically programmed into an assembled device. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. A method for monitoring the storage life of materials;
- said method consisting of;
modeling the thermal degradation characteristics of the material as a function of temperature and time based upon a plurality of experimental data points; using the time-temperature parameters from this model to program a unitized electronic time-temperature indicator device to automatically assess the acceptability of a material'"'"'s thermal history; said device containing computational means, and a temperature measurement means; wherein said device periodically samples the temperature and computes a function of temperature that is continually operative throughout the relevant temperature monitoring range of the device; and wherein said function of temperature approximates the impact that the relevant temperature, for that period'"'"'s length of time, has on a detectable property of said material; and wherein said computational means generate a running sum of said function of temperature over time; and wherein said function of temperature resides with said unitized device; and wherein the granularity of the function of temperature is small enough, and the frequency of time measurements is often enough, as to substantially approximate the impact of time and temperature on the detectable property of said material; and in which said running sum is compared to a reference value, and the result of said comparison is used to generate an output signal indicative of the fitness for use of said material. - View Dependent Claims (23, 24, 25)
- said method consisting of;
Specification