A potentiometer, which avoids problems caused when abraded material collects on the surface of the potentiometer track as a result of friction between the wiper contact and the potentiometer track, causing an undesirable increase in the contact resistance. Potentiometer track and wiper contact wear is also speeded up by this abrasion, which shortens the service life of the potentiometer. The novel potentiometer has a magnet, on a movable extension arm, that removes the abraded material from the surface of the potentiometer track in a contactless manner, thus preventing increased deposition of abraded material on the potentiometer track that would otherwise occur with increased time in operation. The novel potentiometer is especially suitable for air flow rate meters of mixture-compressing, externally ignited or air-compressing, self-igniting engines.
