The thermocouple's behaviour is captured by a characteristic function , which needs only to be consulted at two arguments:
In terms of the Seebeck coefficients, the characteristic function is defined by
The constant of integration in this indefinite integral has no significance, but is conventionally chosen such that .
Thermocouple manufacturers and metrology standards organizations such as NIST provide tables of the function  that have been measured and interpolated over a range of temperatures, for particular thermocouple types (see External links section for access to these tables).