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Published On: Mon, May 26th, 2014

How speedometer of car works eddy current type with working animation video

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Please visit our YouTube channel https://www.youtube.com/user/TechTrixInfo for more tutorial video

This is a video animation tutorial on the working of eddy current speedometers used in automobiles like cars, trucks, buses etc.

First let’s see the components:

  1. Permanent magnet
  2. Speed cup
  3. Stationary field plate
  4. Pointer or needle
  5. Hair spring

Working of eddy current speedometer explained.

how does a speedometer works working animation video eddy current type youtube car truck automobile test motorcycle digital analogue

A well balanced speed cup (blue) is supported by a permanent magnet (green) as shown in the video animation. The spindle is linked with the speed cup and also with a pointer at the dial. The magnet gets its drive from the vehicles transmission through a flexible cable. There for, the speed of the permanent magnet will be equal to the speed of the vehicle. As the magnet rotates, it produces a magnetic field which exerts a torque on the speed cup. The speed cup does not have a mechanical connection with the magnet.

So its clear that, as the vehicle moves, the magnet starts to rotate at a speed proportional to the vehicle speed. This produces a magnetic field resulting in the rotation of the speed cup. As the spindle is connected to the speed cup it also rotates resulting in the rotation of the needle on its top, his needle on the top of the spindle indicated the vehicle speed. The function of the hair spring is to control and limit the movement of the needle and also to bring back the needle to zero as vehicle stops.


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  1. sumanth says:

    Nice explanation..

    • admin says:

      Thank you,if you have any doubt plz drop a comment.
      What’sapp @ +919744615655 for FREE updates on Super Cars, Machines, Mech’/Auto Engg tutorials.

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