What materials are typically used to construct a thermocouple?

Thermocouples are widely used temperature sensors that consist of two dissimilar metal wires joined at one end, where they generate a voltage in response to temperature differences. The choice of materials significantly impacts their functionality and temperature measurement range.

Chromel and constantan are commonly used materials for thermocouples because of their favorable thermoelectric properties, which allow for accurate and stable readings. Chromel, an alloy primarily made of nickel and chromium, and constantan, an alloy of copper and nickel, form a reliable junction that produces a predictable thermoelectric voltage when subjected to temperature gradients. This combination is particularly effective for a range of temperatures, making it a popular choice in industrial applications.

Other materials listed, while they may have their specific applications in thermal sensing or other electrical components, do not provide the same level of reliability and responsiveness as chromel and constantan in thermocouple construction. For instance, copper and aluminum can corrode or provide inconsistent readings under varying temperatures, while silver and gold are costly and not suitable for high-temperature applications typically associated with thermocouples. Iron and nickel, although they form thermoelectric couples, do not offer the same broad usability and stability as the chromel-constantan combination.