Mittarivaihteen

Mittarivaihteen, meaning "speedometer gear" in Finnish, refers to a component within a vehicle's transmission or drivetrain that is responsible for measuring and transmitting the vehicle's rotational speed to the speedometer. Historically, this was often a mechanical system. A small gear, typically made of plastic or metal, would be driven by the output shaft of the transmission. This gear would engage with another gear, which in turn drove a cable. The rotating cable would then transmit the motion to the speedometer head, where a mechanism would translate the rotational speed into a display of the vehicle's speed.

In modern vehicles, mechanical mittarivaihteen systems have largely been replaced by electronic ones. Instead of a physical gear and cable, a speed sensor, often a Vehicle Speed Sensor (VSS), is used. This sensor is typically mounted on the transmission or the axle and detects the rotation of a toothed wheel or a magnetic ring. The sensor then sends an electrical signal to the vehicle's computer (ECU), which processes this information and sends it to the digital speedometer display. While the underlying principle of measuring rotational speed remains the same, the method of transmission and measurement has evolved significantly with advancements in automotive technology.