Resistance temperature detectors (RTDs) are commonly made from which of the following?

Resistance temperature detectors (RTDs) are typically made from materials that have a predictable and stable relationship between temperature and resistance. The most commonly used material for constructing RTDs is platinum due to its stable electrical properties over a wide temperature range. However, in the context of this question, copper is another material used in certain types of RTDs.

Copper is chosen for applications needing lower-cost solutions or for lower temperature ranges, given that its resistance changes with temperature can be accurately measured. In environments where precise temperature readings are crucial, platinum would often be preferred, but copper serves as a practical alternative in less critical or more budget-conscious scenarios.

Gold and aluminum, while they can conduct electricity, do not offer the same desirable characteristics for temperature sensing as copper or platinum. Gold may be used in specialized applications due to its resistance to oxidation, but it is not a common choice for RTDs. Aluminum is generally not used for RTDs because its resistance changes significantly with temperature, making it less reliable for accurate temperature sensing.

Therefore, copper is correctly identified as a common material for RTDs, particularly in various industrial applications where cost and efficiency are balanced considerations.