Thermocouple vacuum feedthroughs are commonly used for temperature measurements in vacuum environments where using a thermometer wouldn’t be practical or data recording is necessary. Thermocouple pressure feedthroughs are also available for application with pressure chambers. For example, thermocouple feedthroughs are ideal for measuring temperatures in vacuum gauges, gas turbine exhaust, diesel engines, fuel tanks, and lab settings.

A thermocouple feedthrough doesn’t directly measure temperature. Instead, it’s used to calculate temperature through a thermoelectric voltage caused by a temperature difference between two ends of the electrical conductor. A thermocouple vacuum feedthrough uses two different metals that conduct electricity at different rates. On one end of the cable a junction is made joining the two dissimilar metals. This junction of the two dissimilar metals creates a voltage that varies with temperature. A temperature can be determined by measuring the voltage between the two wires opposite end of the junction.

Each metal is insulated from the other except at this junction point, which provides a voltage reading. Without proper insulation of the metals, the reading will be inaccurate. With a thermocouple feedthrough, the thermoelectric voltage generated at the sensing junction is transmitted the entire length of the interconnecting thermocouple alloy or compensating material from inside a chamber to an external instrument.