Definition
Temperature-sensing devices made by joining two wires of different metals at one end. When that junction is heated, a small voltage is produced that varies with temperature. In aircraft, thermocouples are used to measure very high temperatures, such as cylinder head temperature in piston engines and exhaust gas temperature or turbine inlet temperature in turbine engines.
Plain English
A small sensor made from two different metals joined together that produces a tiny electrical signal when heated. The hotter it gets, the bigger the signal, so the cockpit gauge can show the temperature.
Context Anchor
Seen in turbine engine instrument discussions, especially where turbine gas temperature or exhaust temperature is being measured.
Derivation
From Greek thermos meaning heat, plus couple meaning a pair joined together. The name describes exactly what it is: two metals paired up to sense heat.
Why Pilots Care
Reliable thermocouple readings let pilots stay within safe engine temperature limits and avoid overheating damage during high-power flight.
Analogy
It acts like a tiny self-powered thermometer that only makes electricity when one end gets hot, feeding the exact temperature to the cockpit display.
Intuition Check
Thermocouples do not heat the engine or control the temperature by themselves. They sense heat and send information to the cockpit instrument.
Example Sentence 1
The exhaust gas temperature gauge gets its reading from thermocouples mounted in the engine's exhaust stream.
Example Sentence 2
During preflight, the mechanic checked that all thermocouples were securely connected so temperature readings would remain reliable in flight.