Definition
An electrical device made up of several thermocouples connected in series, used to produce a measurable voltage from a temperature difference between hot and cold junctions. In aircraft systems, thermopiles are commonly used to sense high temperatures, such as in cylinder head temperature or exhaust gas temperature instruments, and to detect fire or overheat conditions.
Plain English
A small sensor made of multiple temperature-sensing pairs joined together. When one end gets hot, the sensor produces a small electrical signal that can be read on a gauge or used to trigger a warning.
Context Anchor
Seen in discussions of aircraft temperature-sensing systems, heat detectors, and some engine or maintenance instruments.
Derivation
From the Greek 'therme' meaning heat, and 'pile' from the early term for a stack of electrical cells (as in Volta's pile). The name reflects that it is a stack of heat-sensing elements wired together to produce a usable voltage.
Why Pilots Care
Reliable temperature data from thermopiles lets pilots monitor engine performance and avoid overheating in flight.
Analogy
A thermopile is like several small batteries lined up end to end. Each one produces only a tiny amount of electrical push, but together they make a stronger signal.
Intuition Check
Do not picture a pile of hot material. In this term, pile means several small electrical sensing parts connected together.
Example Sentence 1
The cylinder head temperature gauge is driven by a thermopile mounted under a spark plug, which generates a small voltage proportional to engine heat.
Example Sentence 2
During the engine run-up the pilot watched the thermopile output stabilize before takeoff.