A tachometer, or revolution counter, measures the rotation speed of an object within a machine. The value is typically displayed in revolutions per minute (RPM) via analogue dial or digital display. Tachometers are used to measure speed of rotation and some can measure linear speed and distance too. You can learn more in our complete guide to tachometers.How does it measure?Contact tachometers take measurement using physical contact, for example a funnel, wheel or tip. These instruments gather the data for the tachometer. Non-contact tachometers often use a laser or optical disc to measure and are ideal for mobile applications.Tachometers are used in:Machinery AutomotiveTrainsLaser instrumentsLaboratoriesMarine engineering Medicine (blood flow)