| abstract |
This ceramic sheath type thermocouple has a long service life, an improved temperature measuring responsibility and an improved temperature measuring precision, and enables repetitive use. The ceramic sheath type thermocouple has its protective tube 1 formed of a heat resisting ceramics selected from silicon nitride, sialon and silicon carbide. In the protective tube 1 are installed a pair of W--Re wires that are connected to form a joint portion constituting a temperature measuring point 5. A filler made of Si 3 N 4 reaction-sintered ceramics is loaded into the front end portion of the protective tube to enclose the W--Re wires. Another filler made of SiC whisker with a heat conductivity smaller than that of the filler of the front end portion is loaded into the rear portion of the protective tube. An inert gas is sealed in the protective tube. Alternatively, the temperature measuring portion may be formed by exposing from the front end portion of the protective tube the joint portion where the ends of the W--Re wires are connected. The temperature measuring portion is coated with a cover film that is made of silicon carbide, silicon nitride or a composite of these, all having excellent heat resisting and corrosion resisting properties. |