What instrument measures revolutions per minute (RPM) in a vehicle?

A tachometer is the instrument used to measure revolutions per minute (RPM) in a vehicle's engine. It provides real-time data on how fast the engine is spinning, which is crucial for the driver to understand engine performance and to ensure that the engine operates within safe and efficient RPM ranges. Monitoring the tachometer can help prevent engine over-revving, which can cause damage.

In contrast, a speedometer measures the speed of the vehicle in motion, an altimeter gauges altitude, and an odometer tracks the total distance traveled by the vehicle. Each of these instruments serves a unique purpose related to vehicle operation, but only the tachometer specifically focuses on the engine's RPM.