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Temperature monitor for temperature sensitive products

  • US 6,320,512 B1
  • Filed: 11/03/2000
  • Issued: 11/20/2001
  • Est. Priority Date: 11/03/2000
  • Status: Expired due to Fees
First Claim
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1. 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.

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