Abstract: A method and apparatus accurately measures temperature even if a temperature difference exists between cold junctions of the main thermocouple. An auxiliary thermocouple is connected to one leg of the main thermocouple to provide cold junction compensation. Extension leads are connected to both cold junctions to take thermo emf from the thermocouple. The leads are made from a material having a thermoelectromotive characteristic in agreement with the thermoelectromotive characteristic of the other leg at low temperatures at which the cold junction compensation is provided. A converter converts the thermo emf of the composite thermocouple into temperature. The converter can separately set interpolations for converting the thermo emf of the auxiliary thermocouple into thermo emf of the main thermocouple and for coverting the sum of the converted thermo emf and the thermo emf of the main thermocouple into temperature.

Abstract: The invention relates to a method and an apparatus for measuring temperature, using a thermocouple such as a ceramic thermocouple which has no compensating lead wire or has only such a compensating lead wire that is difficult to manufacture. More specifically, the invention is intended to provide a method and an apparatus for accurately measuring temperature even if a temperature difference exists between both cold junctions of the main thermocouple. An auxiliary thermocouple is connected to one leg of the main thermocouple to provide cold junction compensation. Extension lead are connected to both cold junctions to take thermo emf from the thermocouple. The leads are made from a material having a thermo-electromotive characteristic agreeing with the thermo-electromotive characteristic of the other leg at low temperatures at which the cold junction compensation is provided. The invention also provides a converter used to convert the thermo emf of the above-described composite thermocouple into temperature.