ground node

Discussion in 'General Electronics Chat' started by sharanbr123, Oct 29, 2014.

  1. sharanbr123

    Thread Starter Member

    Sep 29, 2014
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    Hello All,

    Can someone help me understand the significance of a ground node.
    Is this more of a representation or a convention or it physically exists.
    If so, why?

    In the figure below, is the GND node at -V volts?
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    To measure the voltage we need two point in the space. One of this point is treat as a reference point (ground GND). We have a very similar situation when we try to measure a height of an object. We need a reference point. The most common reference point is "above mean sea level". But when you try measure the height of the table in your house, now the floor becomes your reference point. So remember that GND is the reference point from which all other voltages in a circuit will be measured.
    http://forum.allaboutcircuits.com/attachments/32-png.70236/

    [​IMG]
    And typically for single supply circuit the GND is at negative terminal
     
    Last edited: Oct 29, 2014
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Ignoring the "what is an earth ground" question, the ground symbol is simply a shorthand notation of what part of a circuit do we choose to measure the voltages with respect to?

    It is also used to unclutter a schematic drawing; all look-alike ground symbols are to be connected together, even though no lines (wires) are shown on the schematic...
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Your symbol is wrong as a power common reference point unless you intend it to be connected to Earth ground.
    There are typically three symbols (ANSI and EIC) that could be used for common although variances take it up to around five.
    Max.
     
  5. sharanbr123

    Thread Starter Member

    Sep 29, 2014
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    Thank you very much, Jony, Mike, MHR,

    I have understood that ground is nothing but a notional node or a reference point. That's all.
    So, when someone says - "make sure system is grounded" what does it mean?
    Is this what Mike is talking about when he says - what is an earth ground
     
  6. Sensacell

    Well-Known Member

    Jun 19, 2012
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    My favorite aphorism is the following: "Ground is not ground the world around"

    Reminds that ground is always a relative concept.
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
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    A ground is considerably more than a reference point, but reference is its principal function.

    When you are studying technical disciplines you learn a number of carefully worded definitions all pitched at the same level, so that you can make sense of how the main players work together.

    As you move on to the next level of study you revisit the definitions, where they are expanded and become more general and you can then see a wider range of interactions.

    The term Earth (UK) or Ground (US) is one such, and it is an important one.

    As you have already realised the limitations of the true and very clear statements already made, I would take this additional statement forward for now.

    The potential of a ground has the additional property that it does not change, within the normal operation of the circuit concerned.

    That is why is so useful as a reference for other nodes in the circuit, which are designed to change in accordance with the workings of the circuit.

    You may read stuff about the resistance of ground, don't go there yet but revisit it at a later date in your studies.

    To answer your question 'What does it mean to be grounded?'
    Simply that the circuit node in question is connected to the best nearby object that will guarantee this constant potential condition. The nearby object may be the planet or it may be the chassis of a vehicle or something else. As already said, in the absence of anything better it may just be one terminal of the power supply that is called ground, but strictly this is incorrect.

    :)
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Here you go....
     
    BR-549 likes this.
  9. BR-549

    Well-Known Member

    Sep 22, 2013
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    Earth ground.......charge neutralizer.
     
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