Abstract: An improved new type pyrometer and a method for fusing an alumina pipe having a high purity are disclosed. The temperature-measuring portion of the pyrometer includes a protective pipe made of alumina having a purity of at least 99.9% and a temperature-measuring resistance element of a platinum or platinum-rhodium resistance wire and a holding portion made of alumina having a purity of at least 99.9%. Owing to the use of high purity alumina, the platinum or platinum-rhodium resistance wire is not contaminated and has stable temperature characteristics at high temperatures. According to the method of this invention, an end of an alumina pipe having a purity of at least 99.9% can be fused without the aid of any binder by fusing the end while evacuating air from the alumina pipe through its opposite end.

Abstract: A resistance thermometer having a resistance temperature detector (RTD) element fixedly supported within a tubular metallic sheath by a compacted insulating material is manufactured by integrally connecting in series two tubular metallic sheaths by pressure welding. The first sheath has a smaller diameter portion which can be inserted into and received by the second sheath. The manufacture method includes the steps of: supporting electrical conductors in the first sheath using the insulating material, electrically joining the RTD element to the conductors supported in the first sheath, putting a metallic ring on the smaller diameter portion of the first sheath, inserting the smaller diameter portion of the first sheath into the second sheath with the RTD element being accommodated within the second sheath, and ramming the metallic ring radially inwardly so that the first and second sheaths are integrally bonded by pressure welding.