Which of the following is used to detect both high and low fuel temperatures in an aircraft?

The use of a thermocouple is essential for detecting both high and low fuel temperatures in an aircraft because it is designed to measure temperature accurately across a wide range. A thermocouple operates on the principle of thermoelectricity, where two dissimilar metals are joined together at one end. When the junction is heated or cooled, it produces a voltage that correlates to the temperature difference.

Due to its ability to provide rapid and precise temperature readings, a thermocouple can effectively monitor fuel temperatures under various operating conditions. This capability is critical for maintaining optimal engine performance and preventing potential issues related to fuel temperature extremes.

While other devices mentioned have their own specific applications, they do not serve the dual purpose of measuring both high and low temperatures. Pressure gauges, for instance, measure pressure rather than temperature, and a Bourdon tube is primarily used for pressure measurement as well. A magneto is used for ignition in aircraft engines, not for temperature sensing. Therefore, the thermocouple is uniquely suited for the task of detecting fuel temperatures.