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Earth or ground? What is the diagram here?

Discussion in 'General Electronics Discussion' started by apples, Aug 29, 2012.

  1. apples

    apples

    88
    1
    Jul 1, 2012
    Here is an part from my cars wiring diagram. What are the symbols here?

    Earth? Earth is always the 4 lines that taper off right?

    What about the other one?
     

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,277
    1,878
    Nov 17, 2011
    Earth (left) is the connection to, well, earth. Generally at one defined point of the circuit or device. This point has to be narked accordingly.
    Ground (right) is used as the reference potential ("0V") within a circuit or device.
    Ground can be connected to earth (and in many cases is) but doesn't necessarily have to.
     
  3. apples

    apples

    88
    1
    Jul 1, 2012
    Okay thanks, I thought it might have been that, just wasn't sure.
     
  4. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Interesting that a car wiring diagram has an Earth ground, since cars are insulated from Earth by the the rubber tires they ride upon...
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    9,277
    1,878
    Nov 17, 2011
    I think Earth is chassis in that case.
     
  6. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    I have no doubt it does, but the question begs why have Earth and Ground designated separately in this case? I suppose it could simply be sloppy diagram work...
     
  7. Harald Kapp

    Harald Kapp Moderator Moderator

    9,277
    1,878
    Nov 17, 2011
    I disagree: While the chassis may be conducting (with the use of modern compound materials this can't be taken for granted) and this conductivity may be good enough for standard electrical wiring, it may be required for sensitive electronic components to have their separate ground. You wouldn't want the return current e.g. from the starter to run through the same conductor the audio amplifier uses, would you?
     
  8. gorgon

    gorgon

    603
    23
    Jun 6, 2011
    As drawn, it indicates a single earth point to the chasis.

    TOK ;)
     
  9. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    I have never seen designated ground conductors in a car for any particular component, besides short jumpers to the chassis from non-conductive items... In all the cars I have seen the battery has two ground wires, one to the engine/drivetrain and one to the chassis/frame... Starters only have a positive conductor, and are engine block grounded when they are bolted up, since they are bolted to the engine they use the engine ground return to the battery, while the rest of the care uses the chassis ground return... Thus the example you gave never happens... This single ground connection to the battery is actually a safety feature, with a single wire removed the entire system is dead...

    Now I fully understand that this kind of grounding has it's drawbacks, but regardless it's industry standard in the automotive field... But, it does bring up a point that maybe the difference here in grounds is the engine vs the chassis...
     
  10. rodrilyx

    rodrilyx

    6
    0
    Aug 29, 2012
    To left is connection to earth and right is to circuit common point (negative)
     
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