Thermocouple Feedthroughs are essential components used in in-vacuum temperature measurement. While not thermocouples themselves, these devices function as air-to-vacuum environmental splices, transmitting the electromotive force (EMF) from a thermocouple through the chamber bulkhead to external instrumentation.

MDC Precision offers feedthroughs compatible with base metal, refractory metal, and noble metal thermocouples, with connector options including miniature, circular MS, push-on, and screw-type designs. These feedthroughs are thermally limited to 450°C (maximum) and constructed with ceramic-to-metal seals, which should not exceed thermal gradients of 25°C/minute.

Base Metal Thermocouples – Environmental Limits

T Type: Copper (+) / Constantan (–), suited for mildly oxidizing and reducing atmospheres. Max operating temperature 400°C. Ideal for low-temperature stability.
J Type: Iron (+) / Constantan (–), suited for reducing atmospheres. Max operating temperature 870°C (largest wires).
E Type: Chromel (+) / Constantan (–), suited for vacuum, inert or mildly oxidizing atmospheres. Max operating temperature 870°C. Highest EMF output among metallic thermocouples.
K Type: Chromel (+) / Alumel (–), suited for clean oxidizing atmospheres. Max operating temperature 1260°C (largest wires).
N Type: Nicrosil (+) / NiSil (–), designed for high-temperature stability. Resistant to preferential oxidation between 1000°C – 1200°C.

Refractory Metal Thermocouples – Environmental Limits

C Type: Tungsten 5%-Rhenium (+) / Tungsten 26%-Rhenium (–). Best for vacuum, hydrogen, or inert atmospheres. Max operating temperature 2760°C.

Noble Metal Thermocouples – Environmental Limits

R Type: Platinum 13%-Rhodium (+) / Platinum (–). High resistance to oxidation and corrosion. Max operating temperature 1540°C.
S Type: Platinum 10%-Rhodium (+) / Platinum (–). Similar to Type R. Max operating temperature 1540°C.

Note: Thermocouple Feedthroughs Types C, R, and S use extension-grade wire rated for 250°C (junction maximum).

Industry Applications

Thermocouple Feedthroughs are widely used across industries requiring precise in-vacuum temperature monitoring. Common applications include semiconductor manufacturing, aerospace engineering, metallurgy, vacuum furnaces, energy research, and laboratory testing systems. These feedthroughs ensure accurate, stable, and reliable temperature readings under demanding conditions where standard sensors cannot operate effectively.