Which of the following devices is NOT a circuit protection device?

Thermocouples are temperature sensors used to measure temperature by generating a voltage based on the temperature difference between two dissimilar conductors. They are critical in monitoring thermal conditions in various applications, especially in aerospace and engineering. However, they do not serve as circuit protection devices.

In contrast, the other options presented—fuses, current limiters, and circuit breakers—are all designed to protect electrical circuits from overcurrent conditions. Fuses work by melting and breaking the circuit when the current exceeds a certain threshold, while circuit breakers can be reset after tripping due to overloads. Current limiters restrict the amount of current flowing through the circuit to prevent damage from excess current. Therefore, thermocouples stand out as devices that measure temperature rather than providing any form of circuit protection.