What device can be used to monitor the performance of a power transmission system?

The device that is most suitable for monitoring the performance of a power transmission system is a speed sensor. This instrument plays a critical role by measuring the rotational speed of various components within the system, such as motors, gears, and shafts. The performance of a power transmission system is often characterized by the speed at which the power is transmitted from one part to another. By keeping track of this speed, the speed sensor can help identify any anomalies or inefficiencies in the system, such as slippage, excessive wear, or potential failures.

In contrast, the other devices listed—pressure gauges, thermometers, and flow meters—are primarily used in different contexts. Pressure gauges monitor the force exerted by fluids in a system, thermometers measure temperature, and flow meters assess the volume of fluid moving through a pipe. While these instruments are vital for their specific applications, they do not provide the necessary data to evaluate the performance characteristics unique to power transmission systems effectively.