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Method and apparatus for calibrating a temperature measuring device by operating a heat source at a preset temperature as determined by a temperature sensing resistor and a digitally calculated temperature which varies nonlinearly with the resistance of the resistor, and obtaining the coefficients f

Method and apparatus for calibrating a temperature measuring device by operating a heat source at a preset temperature as determined by a temperature sensing resistor and a digitally calculated temperature which varies nonlinearly with the resistance of the resistor, and obtaining the coefficients for the calculation by operating the device at a preset temperature and comparing this temperature with that of a standard temperature measuring device.

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In an apparatus for providing a desired temperature for use in calibrating a temperature measuring device, the combination of: a heat source having a receptacle for receiving the temperature measuring device to be calibrated; means for measuring the temperature of said heat source to provide a measu

In an apparatus for providing a desired temperature for use in calibrating a temperature measuring device, the combination of: a heat source having a receptacle for receiving the temperature measuring device to be calibrated; means for measuring the temperature of said heat source to provide a measured temperature, said means including a temperature sensing resistor having a nonlinear relationship between the temperature and resistance of said resistor; means for setting in digital form a desired temperature for the heat source; control means for controlling electric power for connection to said heat source for controlling the temperature of said heat source; a bridge circuit having four arms and two pairs of terminals, with said temperature sensing resistor connected as one arm thereof and resistors of known resistance connected as the other arms thereof, with a known voltage connected across one pair of bridge terminals and providing a differential voltage at the other pair of bridge terminals, which differential sensing resistor; a converter for converting said differential voltage to a digital resistance number; a processor having said digital resistance number as an input for calculating the digital temperature of said temperature sensing resistor as a measure of the temperature of said heat source; said processor including means for comparing said digital temperature of said temperature sensing resistor and said digital desired temperature to provide a digital temperature error signal; and means for converting said digital temperature error signal to an analog signal as an input to said control means for controlling the electric power to said heat source; wherein said processor includes means for calculating said digital temperature of said temperature sensing resistor using known equations with three predetermined coefficients, and including a coefficient memory for said predetermined coefficients, and means for storing values for said coefficients in said memory, and wherein said known equations are the IPTS-68 equations.