Thermocouple feedthroughs
are widely used to measure the temperature in vacuum processes where the
temperature measurement is not made directly but is calculated from the
thermoelectric voltage. The thermoelectric voltage is generated through charge
separation (EMF) caused by a temperature difference between the two ends of
an electrical conductor.
The thermoelectric voltage (depending on the conductor material) is nearly
proportional to the temperature gradient. Thermocouples consist of two
different metals connected at one end.
Using thermocouple feedthroughs the thermoelectric voltage (EMF) is
transmitted from the chamber to an external indicating instrumentation. A high
thermoelectric voltage, corrosion resistance and linearity are decisive factors
for the selection of the material combination.
Noble and base metals as well as alloys - adapted to different application - are
combined in thermocouples. Typical alloys are Alumel® (nickel, aluminium and
manganese), Chromel® (nickel and chrome) and constantan (copper and
nickel).
The thermocouple feedthroughs offered by VACOM are applicable (depending
on the flange connection) in the temperature range from -269°C to 450°C.
