Which instrument is used to measure turbine exhaust temperatures?

Which instrument is used to measure turbine exhaust temperatures?

• A. Thermistors
• B. RTDs
• C. Thermocouples
• D. Bimetal strips

Answer: (C)

Measuring turbine exhaust temperature needs a sensor that can handle very high heat, endure harsh exhaust gases, and respond quickly to rapid engine changes. Thermocouples fit this role best. They work by the Seebeck effect: two different metals joined together produce a voltage that is directly related to the temperature at the sensing junction. This small voltage can be transmitted to the cockpit or a monitoring system with minimal power needs, and high-temperature variants used in jet engines can routinely cope with the intense exhaust conditions and reach the temperatures seen in turbine exhaust. Their rugged construction and fast response time make them reliable for continuous monitoring of EGT. RTDs measure temperature by resistance changes and are very accurate, but they operate in a lower temperature range and respond more slowly in comparison, which is not ideal for the extreme, fast-changing conditions in turbine exhaust. Thermistors are even more nonlinear and have a limited usable range, making calibration across the engine’s full operating spectrum more difficult. Bimetal strips provide only a coarse, mechanical indication and are slow and not suitable for precise continuous readings in the exhaust flow.

Measuring turbine exhaust temperature needs a sensor that can handle very high heat, endure harsh exhaust gases, and respond quickly to rapid engine changes. Thermocouples fit this role best. They work by the Seebeck effect: two different metals joined together produce a voltage that is directly related to the temperature at the sensing junction. This small voltage can be transmitted to the cockpit or a monitoring system with minimal power needs, and high-temperature variants used in jet engines can routinely cope with the intense exhaust conditions and reach the temperatures seen in turbine exhaust. Their rugged construction and fast response time make them reliable for continuous monitoring of EGT.

RTDs measure temperature by resistance changes and are very accurate, but they operate in a lower temperature range and respond more slowly in comparison, which is not ideal for the extreme, fast-changing conditions in turbine exhaust. Thermistors are even more nonlinear and have a limited usable range, making calibration across the engine’s full operating spectrum more difficult. Bimetal strips provide only a coarse, mechanical indication and are slow and not suitable for precise continuous readings in the exhaust flow.