A tachometer is an instrument that measures the working speed of an engine, typically in revolutions per minute (RPM). It is commonly used in cars, boats, planes, and other vehicles. Most tachometer gauges have either an analog (dial) or digital (LCD or LED screen) display.

How does a tachometer work?

It works by bringing a freely spinning wheel in contact with a rotating shaft or disc. The shaft drives the wheel to generate the pulses. These pulses are then read by a tachometer and measured in revolution per minute. It can also calculate the linear speed and distance.

What does your tachometer tell you?

The tachometer indicates how many times the engine is rotating each minute. Multiply the number on the gauge by one thousand. For example, if the needle is sitting at 1, the engine is rotating one thousand times per minute. ... Another situation when the tachometer is helpful is as you are idling.