👉 A tachometer, also known as a speedometer or gauge, is a device that measures the acceleration of an object. It works by measuring the displacement of a moving object over time and converting this into a reading on a scale that shows how fast it's going. When you're driving, for example, your tachometer would show how much distance you've traveled in the last 10 seconds. This is because the tachometer measures the change in position of the car relative to