Abstract: A thermocouple device for detecting a flame. The device includes an outer thermocouple element having an excellent corrosion resistance and a large thermoelectromotive force, an inner thermocouple element, which is inserted into the outer thermocouple element, having a large thermoelectromotive force, and a junction layer securing end portions of the inner and outer thermocouple element. The junction layer is formed with a soldering material so as to avoid the formation of an alloy of the element materials that would have a poor corrosion resistance normally formed by welding.

Abstract: A thermocouple instrument which includes a thermocouple element formed of two dissimilar conductors joined at the ends thereof; an inner protecting metal tube for containing said thermocouple element together with an insulating material and electrically insulated from said thermocouple element via the insulating material; and an outer protecting metal tube in which said inner protecting metal tube is inserted. In this thermocouple instrument, the thermal expansion coefficient of the metal forming said inner protecting metal tube is equal to or higher than the thermal expansion coefficient of the metal forming said outer protecting tube, and accordingly the inner protecting metal tube is rigidly engaged within the outer protecting metal tube with excellent vibration resistance and impact resistance.