Odometer

Mechanical odometer

The display system of the mechanical odometers generally consists of a line of Roue S turning on the same axis. The Chiffre S from 0 to 9 are registered on the circumference of each wheel. A mask is laid out so that one only digit of each wheel is not visible. Each wheel is connected to a system of wheel which makes it turn 10 times less quickly than its neighbor of right-hand side, from where a counting decimal. In a car, knowing the Circumference wheels of the vehicle, one can deduce the distance covered by this last. In practice, a cable transmits the rotation of the secondary tree of the gear box to the odometer of the instrument panel or a whole of wheels provides the suitable reducing factor.

The recording reading devices with magnetic band, such as Tape recorder S, Video tape recorder S, etc. , are also equipped with odometers, allowing to locate on the tape the site of a recorded passage. They measure either passed time, or the length of band which ravels. The meters of this type are mechanically interdependent of the tape motion. Thus, according to the manufactures quality, the meter will be more or less faithful.

Electronic odometer

There are two ways of doing function an electronic odometer:

Is by preserving the old mechanical system (a push-pull cable connecting the exit of pin to the odometer Tachymètre, which is him provided in entry with a Capteur transforming this rotation into Impulsion S electric).
Is as on the last generations of vehicles, whose sensor is integrated into the Gear box or another Organe allowing the velocity measurement and the distance covered. The sensor is him connected by simple a wire transmitting the Signal to the odometer.

Calibrations and errors

All these systems of measurement can be distorted during a pneumatic change of S, if one goes up on the driving wheels of the tires having a Circonférence different from those assembled of origin.

To solve this problem, one can add a partial electronic odometer (and sometimes also total) adjustable by computer, similar to a Taximètre. These odometers have the following characteristics:

They can be sealed by a workshop entitled legally and, to be legally used with business ends. It is prohibited legally to use to this end, an odometer which is not controlled and is not sealed);
They can carry a control of each partial value before the setting in zero (for Remise S);
the models intended for the Heavy truck S and the vehicles of Public transport comprise a speedometer instantaneous as well as a permanent recording of this one, allowing controls;
They can also be placed in manner more visible (freight vehicles of loads and people).

Podometer

With the difference of the odometer, the Podomètre does not count turns, but the number of not , thanks to an oscillator. It is necessary to record as a preliminary the average length of the step in order to obtain a distance rather right. There exist mechanical and electronic podometers.

See too

Tachograph
Speedometer Tachometer

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