Speedometer
The Speedometer or " meter of vitesse" is a instrument allowing to indicate the Speed of displacement of a Véhicule. Practically all the Automobile S, Motor cycle motorized S and other machines are equipped with it. In a car, one very often just finds it behind the Stealing, sometimes in the center of the Instrument panel.
General presentation
The function of the speedometer is to make it possible the driver to know the instantaneous speed of its vehicle. The speedometer is very useful to make it possible the driver to control the speed of sound Véhicule compared to the limits imposed by the Signalisation or the Highway code. In France, the Speed is indicated in Kilomètre per hour (km/h). In certain countries, the speedometers have a double Graduation: the local Measuring unit (generally the mile) and the international measuring unit.In certain cases, the speedometer comprises additional graduations intended to inform the driver on the report/ratio of Gear box which should be committed. These indications summarily allow stage the absence of Compte-tours. For example, the first speed in lower part of 20 km/h, it second between 20 and 45, the third between 45 and 70 etc…
Several types of speedometers
One generally distinguishes three types of speedometers according to posting:
- round Meter with Needle
- linear Meter with needle
- Numerical Meter
The round meter is most current. A Odometer adding and daily, or mileage odometer , is logically integrated to him. It has the advantage of being easily readable of a simple glance. On all the vehicles the speedometer is enlightened to facilitate its reading in Conduite of night.
The linear needle meter is appeared as a horizontal Graduation linear on which the needle moves. Its main advantage is a certain compactness compared to the round meter. Enough widespread in the Sixties and Seventies, the linear meter seems to be last of mode.
The digital meter or numerical poster directly the value speed on a screen of the Instrument panel. Its indications are more precise than those of the needle meters. Its principal uses are the following ones:
- This type of indicator is very current on the vehicles of competition;
- One finds it on certain models of the group FIAT of the Années 1980 and 1990 (FIAT Tipo);
- From now on it is sails very about it since 1993, the model Twingo of Renault having started again the fashion.
In the Aviation, one uses an apparatus which gives the relative speed of the air, the Badin or Anémomètre.
Calibration and errors
The motor vehicles leaving the chains are currently equipped out of standard with electronic calculators speed. Some show them to be less precise than their mechanical counterparts. Completely unfounded assertion, concerned systems comprising only one tiny margin of error, taking into consideration margin ascribable to the old completely mechanical systems.On the other hand these systems of measurement electronics are regulated by defect to post a rate of travel higher of approximately 10% at the real speed, this for safety requirements road, moreover, the mechanical systems were preset in the same way.