Non-contact tachometers, sometimes called photo tachometers, use a laser or other light source to illuminate the rotating part. This light reflects off of a marker that is temporarily affixed to the rotating part and brightly reflects the light to the tachometer. This allows for accurate measurements without adding drag or resistance to the rotational speed.

Contact tachometers directly measure rotational speed by contacting the rotating part and measuring its speed. This ensures accurate readings in environments that are dusty, dirty, moist, or could otherwise affect optical and magnetic tachometers.

Combination contact and non-contact tachometers provide direct and indirect methods of measuring rotational speeds. This allows them to be used for low- and high-torque applications.