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Circuit ground

by john ross
Tags: circuit, ground
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john ross
Feb19-10, 10:52 PM
P: 2
Im very confused when I see schematic diagrams with ground symbols. In my understanding, those ground symbols are placed in the negative connection in the circuit . Can someone explain me what are "grounds" for?
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Feb19-10, 11:15 PM
Sci Advisor
P: 4,046
Unless it is a radio device where the real ground makes a difference, "ground" really just means that these points can be joined together or touched by humans without affecting the circuit operation (or the humans).

Normally, there will be a substantial area of metal which is used for bypassing purposes.
This may be an actual metal case or it may be a portion of a printed circuit board copper coating which has not been etched.
Incoming shielded cables would have their shield connected to this "ground" and pins of ICs etc that were marked as "ground" would be connected to this area as well.

Because the different areas of this ground have negligible resistance between them, they can be regarded as the same point for most circuits. For very high frequency circuits, the inductance beteen various points on the "ground plane" have to be allowed for in the circuit layout.

In portable applications such as battery operated equipment, this metal area does not have to be connected to the actual ground or even to a mains supply ground.

If the apparatus was mains powered, this metal case would have to be grounded in accordance with wiring regulations.
Feb20-10, 01:25 AM
P: 422
Just remember that voltage is relative and ground is used as a base reference so to say.

john ross
Feb21-10, 05:24 AM
P: 2
Circuit ground

ok thanks for the brief explanation

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