Power ground

Discussion in 'Electronics Resources' started by BRAWNEY, Jul 24, 2013.

  1. BRAWNEY

    Thread Starter New Member

    Jul 24, 2013
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    What is the actual definition for a power/ground in a dc circuit? :confused:
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Early developers of electrical systems theorized that the earth was an electrically neutral body, i.e. an equal number of negative and positive charges are distributed throughout the earth at any given time.

    Being electrically neutral, earth is considered to be at zero potential and establishes a convenient reference frame for voltage measurements.

    Noting that voltmeters read only the difference in potential between two points, absolute measurements can be made by using earth as a reference.
    A true earth ground, as defined by the National Electrical Code, physically consists of a conductive pipe or rod driven into the earth to a minimum depth of 8 feet.

    http://forum.allaboutcircuits.com/showthread.php?t=86932&highlight=grounding
    Also if you want a definitive reference Eustance Soares - Book on Grounding
    Max.
     
    Last edited: Jul 24, 2013
  3. Ramussons

    Active Member

    May 3, 2013
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    I've seen an inverted T as a "ground" - same as a Signal Ground . . . .?

    Ramesh
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    This is usually the equivalent as Chassis common as shown in the PDF.
    IMO if the common is not actually at earth ground, any of the other symbols should be used and preferably identified in some way, especially if there are two or more systems integrated together with power supplies that are isolated from each other.
    The various supply positives are usually readily identified +5v +24v etc, but the commons rarely get the same treatment for some reason?.
    Max.
     
  5. #12

    Expert

    Nov 30, 2010
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    Here are 4 ground symbols. I tend to use the second one as circuit ground because I can write a number in it to signify different circuits. I use the first one for Earth ground and the third one as chassis ground. I think the fourth one is a European style.
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
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    +1. I only see this in european prints. I read it as circuit common, not earth ground.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Yes, the European symbol for Earth Ground is the same as N.A.
    Max.
     
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