# 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?

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.

Also if you want a definitive reference Eustance Soares - Book on Grounding
Max.

• ###### GndSymbols.pdf
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3. ### Ramussons Well-Known Member

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

Ramesh

Jul 18, 2013
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5,884
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.

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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.