Typically, once you've measured a particular thermocouple millivoltage, you will go to published standard thermocouple tables to look up the temperature. The other alternative is to find temperature given millivoltage using polynomial approximation formulas.
However, reversing that process can be quite useful. Thermocouple performance can be simulated by outputting the millivoltage for a specified temperature. By simulating the thermocouple in that fashion, you don't have to actually immerse a thermocouple in a controlled thermal environment.
With this simple program (see the figure), the millivoltage for a given temperature can be found using an iterative loop and the 8th-order polynomial approximation for a type-K thermocouple.
Several comparisons to table values are made to illustrate the level of accuracy obtained with this method (see the table). Alternative thermocouple types and their respective polynomials can be substituted into this program.