A complete thermocouple temperature sensing assembly, in accordance with the present state of the art, consists of one or more of the following: A. Sensing Element Assembly B. Protecting Tube C. Thermowell D. Terminations E. Miscellaneous Hardware.

Compacted ceramic insulated themocouple material consists of three parts as shown in Fig. 5.1. This type of thermocouple is in common use because it isolates the thermocouple wires from environments that may cause rapid deterioration and provides excellent high-temperature insulation for thermocouple wires. The sheath can be made of a metal compatible with the process in which it is being used and provides mechanical protection. The material is easy to use because it forms easily, retains the bent configuration, and is readily fabricated into finished thermocouple assemblies.

When data were being gathered in 1961 for National Bureau of Standards Monograph 40 [3] on Thermocouple Materials, a section was included to cover ceramic packed thermocouple stock "because of the wide use and increasing popularity." New uses continue to be found for this unique hetrogeneous materials combination. Compacted ceramic insulated thermocouple material consists of three parts as shown in Fig. 21. The advantages of this configuration are: 1. It isolates the thermocouple wires from environments that may cause rapid deterioration. 2. It reduces long term calibration drift. 3. It lessens temperature versus wire size problems. 4. It provides an excellent high temperature insulation for thermocouple wires. 5. The sheath can be made of a metal compatible with the process in which it is being used and bears the brunt of the environmental effects. 6. It is easy to use: a. Forms easily and retains the bent configuration. b. The sheath can be welded without loss of insulation. c. Available in a wide variety of sizes and materials. d. Readily fabricated into finished thermocouple assemblies with minimum of technique and equipment. e. Useful at high pressures or high temperatures or both. 7. It is inexpensive as a finished thermocouple.

A complete thermocouple temperature sensing assembly, in accordance with the present state of the art, consists of one or more of the following: A. Sensing Element Assembly--In its most basic form this assembly includes two dissimilar wires, supported or separated or both by electrical insulation and joined at one end to form a measuring junction. Such assemblies usually fall into one of three categories; (1) those formed from wires having nonceramic insulation, (2) those with hard-fired ceramic insulators, and (3) those made from sheathed, compacted ceramic-insulated wires. This chapter will deal only with the first two. See Chapter 5 for complete details on the latter.