Which metals are used in the construction of an EGT (Exhaust Gas Temperature) sensor?

The correct choice is based on the specific properties and applications of different metals in thermocouple technology, particularly for measuring exhaust gas temperature in turbine engines. Chromel and Alumel are alloy combinations that are commonly used for thermocouples because of their favorable thermal and electrical properties.

Chromel is a nickel-chromium alloy, while Alumel is a nickel-aluminum alloy. These materials are specifically chosen for their high-temperature stability and their ability to generate a reliable thermoelectric voltage when exposed to heat. This combination allows for accurate and consistent measurements of exhaust gas temperatures, which is vital for monitoring engine performance and ensuring safety.

The other options include metals that do not have the same level of suitability for high-temperature sensor applications. For instance, nickel and copper, while they have good electrical conductivity, do not perform as well at the elevated temperatures experienced in turbine exhaust environments. Iron and steel are also not ideal due to their susceptibility to corrosion and degradation at high temperatures, and titanium and brass, while they have their uses, do not have the thermoelectric properties required for effective temperature measurement in this context. Thus, the use of Chromel and Alumel alloys is the optimal choice for EGT sensors.