There are various ways to graduate thermocouples, as with most other thermometers. The first method is to measure the thermocouple voltage at several reference points and interpolate according to the accepted formula, or according to deviations from the standard table.
Another technique is to compare the readings of a graduated thermocouple with a thermocouple of the same type, taken as a standard. In a relatively large number of points and plot either a curve of deviations from the reference graduation, or a direct dependence of the thermocouple voltage on temperature.
Standard reference tables play an important role in thermocouple temperature measurement and save a lot of time and labor.
The standard table describes the behavior of a typical thermocouple of a particular type.
The graduation of a working thermocouple of this type is reduced to finding the deviations of its readings from the standard ones given in the table.
The deviations turn out to be very small if the initial data for creating the standard table are reliable, and if the graduated thermocouple manufactured with the same alloys composition as in the standard table.