How odometer works?
An odometer tells you how many miles/kilometers you have
traveled
The old/mechanical type of odometers work by a cable that turns
a bunch of gears that create an INCREDIBLE gear ratio. When the
cable turns, the cable turns the gear train which therefore turn
the numbers. Unfortunately, the great disadvantage of such devices
are that they can be roll backwards by using a drill and turning
the cable backwards, (or forwards so the numbers can roll back to
0), or just simply driving the car backwards. Also, it's not very
accurate.
The newer type of odometers, electronic/computer, work by using
two magnets, one attached to the spokes of the wheel, one attached
to the car itself. Every time the wheel spins once, the magnets
make a close contact and an electric charge is made. A computer
inside counts how many contacts are made then calculates the total
distance depending on how long the spokes are and how many
revolutions were spun.
The above is the same for bicycle odometers, except the computer
has to be programmed to the length of the spokes.
For an electronic odometer, it's harder to "rollback" the
odometer because the ECU (engine control unit) will store the
number. Therefore, if someone tries to "rollback" the number, the
stored value in the ECU will disagree; this value can be detected
in all car-dealership companies.
The above does not state whether you can hack the ECU so the
number will change, or changing the ECU itself with a newer
one.
References
- Me
- HowStuffWorks
- Wikipedia