NCCER Millwright Practice Exam

What type of instrument is used to measure rotational speed in machinery?

1. Speedometer

2. Accelerometer

3. Tachometer

4. Manometer

The correct answer is: Tachometer

In machinery, a tachometer is specifically designed to measure the rotational speed, providing essential information about how fast an object is spinning, typically in revolutions per minute (RPM). This instrument plays a crucial role in monitoring and controlling processes that depend on precise speed, ensuring optimal performance and preventing potential damage due to overspeed conditions. While a speedometer measures the speed of a vehicle, often in miles per hour or kilometers per hour, it is not suitable for measuring the rotational speed of machinery components. An accelerometer is used to measure acceleration forces, which involves changing speed rather than the constant rotational speed itself. A manometer measures pressure, particularly in fluid systems, and does not pertain to rotational speed whatsoever. Thus, the tachometer is the appropriate tool for measuring the rotational speed in machinery applications.