how do speedometers work?
In: Technology
Traditionally they’d be made with something called a d’arsonval meter. Basically a metal coil, a magnet, and a spring. Put more current through the coil and it rotates against the spring, put less and the spring pulls it back. So the angle of the turn correlates to the amount of current applied.
Then you have a wired coil on your axle spinning in a magnetic field and it will generate a current that corresponds to your speed (or at least the speed of your axle). Put the two together and you have a surprisingly accurate measurement of speed.
Today, they probably do something similar but with an analog to digital converter in there somewhere that digitizes the axles speed and sends it to the dash as a digital signal.
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