What physical feature of a thermocouple ensures mechanical protection for its components?

The correct answer highlights that a metal cage serves as a robust mechanical protective feature for the elements of a thermocouple. Thermocouples are designed to measure temperature by generating a voltage based on the temperature difference between two junctions of different metals. Given that these junctions can be sensitive to physical damage, a metal cage offers significant durability against external impacts and environmental factors.

This protective feature is particularly important in industrial settings, where thermocouples may be exposed to harsh conditions, including vibrations, extreme temperatures, and chemical exposure. The metal cage provides a strong barrier that can resist damage while allowing the thermocouple to effectively sense temperature changes. Additionally, it helps avoid interference from electromagnetic fields and protects the sensitive junctions from debris or contact that could lead to inaccurate readings or failure.

While other materials like rubber, plastic, or glass may offer varying degrees of protection or insulation, they do not provide the same level of mechanical strength and durability as a metal cage. Therefore, the selection of a metal cage as the protective feature is crucial for maintaining the integrity and function of a thermocouple in demanding applications.