(HP-67) Thermocouple EMF↔Temperature Conversion

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An extract from Calculator Thermometer, University of Tennessee (Physics Department) {DOE-Oak Ridge NL}

"ABSTRACT
An inexpensive substitution for calibrated thermocouples, linearizing electronics, and the N. B.S. thermocouple tables is obtained through the use of a hand-held calculator …
… Programmable calculators with as few as 16 program steps and three addressable memories may be used for one way conversion over a limited temperature range. If as many as nine addressable memories are available, the calculator may be programmed to choose the appropriate set of constants from the storage registers for three different temperature ranges. With an HP 67 or 97 calculator, sufficient memory is available to allow storage of copper-constantan or iron-constantan constants for all temperature ranges and the flexibility of one button conversion of thermocouple voltage to Kelvin, Centigrade, or Farenheit temperatures and vice versa …
… For many measurements, it is convenient to have a reference bath at a temperature other than 0°C. The program may be written to incorporate this possibility … small variations … due to fluctuations … The program can be designed to incorporate these variations from run-to-run or long-term discrepancies as desired …
In some cases it is desired to stabilize a sample at a chosen temperature T. By using Eqn. (1) and the inverse of Eqn. (4), the inverse linear correction may be applied to find the voltmeter reading the thermocouple should produce. The magnetic card stored HP-67 program provides this one button calculation …
The program and constant cards have been submitted to the Hewlett-Packard Corporation for distribution thru its user library facility."

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