External instrumentation can then evaluate the strength of the emf that is proportional to the temperature at the thermocouple bead, thus yielding a temperature measurement. The CeramTec thermocouple feedthrough provides the necessary electrical isolation and a hermetic seal.

For refractory and noble metal thermocouples CeramTec uses compensating wires. The joints between the compensating material and the true thermocouple conductor material must be thermally shielded and not exceed 250° C. Observe the maximum temperatures stated in footnotes for the part chosen. A Thermocouple Application Chart is shown on the next page.

Materials and Processes

CeramTec thermocouples use only inorganic materials. The insulators are high-purity, high-strength, low-loss alumina ceramics. Hardware metals include Kovar®, stainless steel, nickel, copper, nickel-iron alloys, cupro-nickel alloys and molybdenum. Conductor materials and contacts include Chromel®, Alumel®, Alloy 405, Alloy 426, Alloy 11, copper, Constantan® and iron. Compensating wires, Alloy 11, copper, Alloy 405 and Alloy 426 are utilized in types C, R and S feedthroughs.

Braze materials include silver, copper, silver-copper and gold-copper alloys. Metallization processes include both refractory-metal and active-metal metallizations, dependent upon size, geometry and performance requirements for the seals. CeramTec uses advanced techniques for control of special and critical processes, including 100 percent helium leak testing, and x-ray measurements for metallization control.

Standard Specifications

• Temperature Range: Cryogenic (-269° C) to 450° C
• Internal pressure from 10-10 torr to 3,500 psig
• Thermocouple Type C, E, J, K, R, S,T
• Single to 20 pairs

Extreme / Custom Design

• 940-pin feedthrough using thermocouple materials
• Sub D connectors using thermocouple materials
• Single pair high-temperature cable end seal in a special plug design

Installation

Standard installation mountings include:

• Weld (Pulse-TIG,TIG, Laser, E-Beam)
• ISO KF flange
• ConFlat flange
• NPT fitting (see Pressure section)
• 1" Baseplate (see Baseplate section)

For details and information on thermocouple assembly installation, refer to the Technical Reference section.

Applications

A few of the many applications in which these thermocouples are commonly used are:

• Furnaces
• Power generation measurement and control
• Aerospace equipment
• In-vacuum coating
• Semiconductor processing equipment
• Energy research
• Industrial equipment

New Products

• Multipin spade type thermocouples
• Header style thermocouples
• Single conductor thermocouples in spade and loop type
• Thermocouples now available in ISO KF flanges

Typical Thermocouple Construction

Selecting the Right Thermocouple

To select the right thermocouple for your applications, you should consider:

• Number of thermocouple pairs
• Operating temperature
• Installation
• Plug requirements, single- or double-ended
• Dimensional characteristics
• Any other specific considerations, e.g., non-magnetic, cryogenic