Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-11-03
2001-11-20
Trieu, Van (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S589000, C340S521000
Reexamination Certificate
active
06320512
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to temperature monitoring devices.
2. Prior Art
Some temperature sensitive products must be shipped and stored within strict temperature limits. For example, according to FDA (Food and Drug Administration) regulations, freshly drawn whole blood must be cooled from body temperature down to a storage temperature range of between 1-6 degrees Celsius within 6 hours. The temperature range during shipment can be between 1-10 degrees Celsius. In addition, the blood temperature must decline in a continuously downward trend when cooling toward the shipping and storage temperature ranges. Many other pharmaceutical products also have temperature and cooling trend requirements.
Various temperature monitors have been specifically made for monitoring pharmaceutical products. Some are simple data recorders that record a numeric temperature history over time. The data must be interpreted by a trained technician, and often requires an external computer to perform the analysis. Other devices provide alarms that are triggered if the temperature is out of an acceptable range, or out of range for a predetermined period of time. The alarm may not be produced if the temperature trends upward for less than the predetermined time, wherein such an upward trend is in violation of FDA regulations. An example of such a device is disclosed in U.S. Pat. No. 5,313,848 to Santin et al.
OBJECTIVES OF THE INVENTION
Accordingly, the objectives of the present temperature monitor are:
to monitor the temperature of a temperature sensitive product;
to activate a first acceptable condition indicator if the temperature is cooled to an acceptable range within an acceptable time period;
to maintain the first acceptable condition indicator if the temperature is reduced in a continuously downward trend fast enough to reach the acceptable range within the acceptable time period;
to activate an alert indicator if the temperature does not reach the first acceptable range within the acceptable time period;
to activate the alert indicator if the temperature has had an upward trend prior to reaching the acceptable range;
to activate a second acceptable condition indicator if the temperature rises from the first acceptable range to a second acceptable range;
to activate an over temperature indicator if the temperature rises above the second acceptable range;
to activate an under temperature indicator if the temperature falls under the first acceptable range;
to latch on the worse condition indicator and never return to better condition indicators once the worse condition indicator is activated;
to be compact enough for being sandwiched between products; and
to be simple and inexpensive to manufacture.
Further objectives of the present invention will become apparent from a consideration of the drawings and ensuing description.
BRIEF SUMMARY OF THE INVENTION
The present temperature monitor is comprised of a thermistor and a reference resistor connected to a capacitor in parallel. The capacitor is charged through the thermistor by a microcontroller to determine the thermistor charging time, discharged, and then charged through the reference resistor to determine a reference charging time. The thermistor charging time is divided by the reference charging time to determine the thermistor value, which is converted into an actual temperature by using a conventional algorithm. The microcontroller is programmed to activate various indicators to show the ambient temperature relative to one or more acceptable ranges, whether the temperature has reached the acceptable ranges within an acceptable time period, and whether the temperature has had an upward trend prior to reaching the acceptable ranges.
REFERENCES:
patent: Re. 36200 (1999-04-01), Berrian et al.
patent: 4685614 (1987-08-01), Levine
patent: 5262758 (1993-11-01), Nam et al.
patent: 5313848 (1994-05-01), Santin et al.
patent: 6046674 (2000-04-01), Irwin et al.
patent: 6058356 (2000-05-01), Swanson et al.
Newton Ronald
Nicholson Larry
Tyner Cliff
Lo Jack
Nicholson Larry
Trieu Van
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