US 6,320,512 B1Granted

Temperature monitor for temperature sensitive products

AssigneesLarry Nicholson, Cliff Tyner

InventorsLarry Nicholson, Cliff Tyner, Ronald Newton

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Abstract

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.

Claims7

Dependent claims

A temperature monitor, comprising:

a microcontroller;
a thermistor with a first end connected to a thermistor pin on said microcontroller;
a reference resistor with a first end connected to a reference pin on said microcontroller, and a second end connected to a second end of said thermistor;
and
a capacitor connected to a junction between said thermistor and said reference resistor;
wherein said junction between said thermistor, said reference resistor, and said capacitor is connected to a sample pin on said microcontroller;
wherein said microcontroller is arranged to:
charge said capacitor only through said reference resistor until a predetermined voltage at said sample pin is reached;
measure a reference charging time taken to reach said voltage;
discharge said capacitor;
charge said capacitor only through said thermistor until said voltage at said sample pin is reached;
measure a thermistor charging time taken to reach said voltage;
compute a thermistor value by dividing said thermistor charging time by said reference charging time to eliminate errors caused by capacitor variances;
and
converting said thermistor value into a corresponding temperature.

12 more elements

Dependencies are inferred from the claim text.