This is a minimal thermocouple schematic. An op amp amplifies the tiny voltage that is created when one of the two thermocouple wire junctions is hotter than the other.
As opamp you can use the very popular CA3130/CA3140 ..
Another example ( http://www.nhsouth.com/crafts/workbench/thermocpl.htm ) shows you practical application of thermocouple/opamp(s) based temperature control circuit ..