How does an RPM indicator display its readings?

The RPM indicator is designed to provide relevant information about the rotational speed of a component such as an AC generator. It commonly displays readings as either a percentage of its maximum capacity or directly in RPM, depending on the design of the system and the specific application. This dual display is particularly useful in monitoring performance and efficiency, allowing operators to easily assess how close the machine is to its operational limits.

When dealing with AC generators, showing the output in percentage can help users understand how much of the generator's capabilities are being utilized. The RPM value provides a direct measurement which is critical for operational control. Therefore, indicating rotational speed both as a percentage and in RPM is aligned with the needs of operators in monitoring and adjusting generator performance.

In contrast, the other options do not accurately reflect typical RPM indicator functionalities. For example, a specific focus on RPM for DC motors limits the wider capabilities of the indicators. Additionally, presenting data solely in voltage and current measurements does not give direct insight into the rotational speed. Lastly, expressing information as a numerical value only fails to convey the necessary context that percentage readings can provide. These contexts are pivotal in maintaining effective operational levels across machinery.