What is ground?

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,777
On another thread I postulated that we call ground "Zero" volts. But I contend that what we call zero volts may in actuality some much greater potential. Keep in mind the key is Volts, not current. Current flows when there's a differential potential between two points. Whether static or a dynamic charge, there's a potential. It's possible to have a grounded device that is statically charged. Not grounded in reference to earth ground, just a common ground. Which we all would agree doesn't mean zero volts. OR maybe it IS zero volts. It's whatever we want it to be. Like Shrodinger's cat. Left in a box for years we surmise it's probably dead. But we don't know that for certainty until we open the box. Thus a condition is unknown until it's measured. When measuring the activity of an atom we can only see it in an instant of time. Stringing a series of instances together we can get a motion picture, but just like a motion picture it's still one frame at a time. So voltage when measured is X volts at a given time.

Let me be clear; I'm way over my own head with this. I may be 10,000% wrong. I'm just posing a question to see where this goes. Maybe I'll learn something. There are plenty of members of AAC who are vastly more educated than I am. But education doesn't mean intelligent. Smart by life or by book, we all have something to contribute. Even smart by education. Not being educated to the same degree as another doesn't make one "not smart" or "dumb" as some might say.

So since I started an argument on another thread - what do you think ground is? Sure, there's the basic description of ground, being a common point or a zero point. But it's the point at which we start measuring some fictitious value. A battery of 1.5 volts has a potential difference of 1.5 volts from positive to negative. We often reference negative as ground. But if that battery has become statically charged to 3KVs (3,000 volts static) then from negative to COMMON ground we see 3KV. But from the positive terminal we see 3,001.5V. The potential between battery poles remains the same but all the while it's statically charged. So calling negative "ground" we're not talking about a real world situation where absolute ground is absolutely zero volts.

Your thoughts? Arguments? Agreements or disagreements?

Note: It's perfectly acceptable to disagree and argue. As long as we respect each others opinions and positions of beliefs in electronic terms.
 

BobTPH

Joined Jun 5, 2013
8,664
The definition of voltage does not allow for any absolute voltage. Voltage is the difference in potential between two measuring points. It is the energy gained or required in moving a charge from one place to another. It is always defined as a difference.

Ground is simply a potential the we arbitrarily use as a consistent reference to measure other potentials against. When we measure the voltage at ground, it is the the difference in potential between ground and ground, in other words, zero.
 

crutschow

Joined Mar 14, 2008
34,047
Don't see any big discussion on this.
Circuit common or ground is just the reference point to which we measure all other voltages.
It's only "zero volts" when measured to itself, which obviously measures zero.

If "ground" is at some large potential to some other arbitrary point that doesn't affect the circuit measurements to its ground.

Don't know what you mean by a "fictitious value".

There is no such thing as "absolute ground".
All voltages are measured with respect to another point.
How could one point be "absolute"?
 

MaxHeadRoom

Joined Jul 18, 2013
28,513
What I have an issue with is the term Ground use indiscriminately to refer to Earth Ground & chassis GND, along with the symbol for earth GND also used in the same manner.
Where I came from the term Earth was used in circuits and installations to indicate a conductor that terminated at Earth GND point.
e.g. you ran a Earth wire, NOT a ground wire.

Here is a couple of good comments on the terms.
U of PENN &
Page 22 of Dr Archambeault
 

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MaxHeadRoom

Joined Jul 18, 2013
28,513
I do have one problem with the first symbol in the Archambeault publication, however is on p36, No1 "Circuit ground" should be Earth.
 

djsfantasi

Joined Apr 11, 2010
9,151
Ground is not a concrete value. It is but a word, used to reference something. The word is used relative to voltage, which requires two points to be meaningful. And ground is a single point. So it’s easy to see that depending on what the other point is, the value for ground could be anything or nothing.
 

WBahn

Joined Mar 31, 2012
29,863
On another thread I postulated that we call ground "Zero" volts. But I contend that what we call zero volts may in actuality some much greater potential. Keep in mind the key is Volts, not current. Current flows when there's a differential potential between two points. Whether static or a dynamic charge, there's a potential. It's possible to have a grounded device that is statically charged. Not grounded in reference to earth ground, just a common ground. Which we all would agree doesn't mean zero volts. OR maybe it IS zero volts. It's whatever we want it to be. Like Shrodinger's cat. Left in a box for years we surmise it's probably dead. But we don't know that for certainty until we open the box. Thus a condition is unknown until it's measured. When measuring the activity of an atom we can only see it in an instant of time. Stringing a series of instances together we can get a motion picture, but just like a motion picture it's still one frame at a time. So voltage when measured is X volts at a given time.

Let me be clear; I'm way over my own head with this. I may be 10,000% wrong. I'm just posing a question to see where this goes. Maybe I'll learn something. There are plenty of members of AAC who are vastly more educated than I am. But education doesn't mean intelligent. Smart by life or by book, we all have something to contribute. Even smart by education. Not being educated to the same degree as another doesn't make one "not smart" or "dumb" as some might say.

So since I started an argument on another thread - what do you think ground is? Sure, there's the basic description of ground, being a common point or a zero point. But it's the point at which we start measuring some fictitious value. A battery of 1.5 volts has a potential difference of 1.5 volts from positive to negative. We often reference negative as ground. But if that battery has become statically charged to 3KVs (3,000 volts static) then from negative to COMMON ground we see 3KV. But from the positive terminal we see 3,001.5V. The potential between battery poles remains the same but all the while it's statically charged. So calling negative "ground" we're not talking about a real world situation where absolute ground is absolutely zero volts.

Your thoughts? Arguments? Agreements or disagreements?

Note: It's perfectly acceptable to disagree and argue. As long as we respect each others opinions and positions of beliefs in electronic terms.
You get to pick ONE point in the entire universe and arbitrarily assign a value to the voltage that the one point. The values of the voltages at every other point in the universe is now keyed to the decision you made.

When you say that the battery has become statically charged to 3 kV, that 3 kV is measured relative to what?

If you have already declared the negative terminal of the battery to be your 0 V reference, the whatever you are talking about when you talking about this 3 kV static charge is now at -3 kV.

The beauty of this is that you and I can be talking about the exact same circuit and we can choose different ground references and we can still agree of everything except voltage AT a point -- they will differ by a fixed amount. But that's fine, because voltage at a fixed point is meaningless -- voltage, by it's very definition, is a potential difference between points, and on those values we will agree completely.
 

WBahn

Joined Mar 31, 2012
29,863
Ground is what you have after you grind.
So I can have a pound of ground?

Sounds like something I'd go to a butcher's shop to get.

I'd offer up that what you have left after you grind are the groundings (grindings?).

Unless you are in certain parts of New Mexico, in which case maybe they're groundlings.
 

MaxHeadRoom

Joined Jul 18, 2013
28,513
Back in the 1950's the JIC attempted to define the symbols used today, and the Earth GND symbol shown in #11 was specifically defined as any conductor or circuit connected to earth GND.
Or any metallic part of a system that had contact with earth GND via a specific conductor or other definite means.
 

WBahn

Joined Mar 31, 2012
29,863
The electrostatic field potential at infinity is assumed to be zero. So I guess that's the 'real' Ground.
I don't think it's an assumption in the sense that we somehow "believe" it to be zero there and just can't prove it, but rather just an arbitrary definition that has no more or less validity that sticking a rod in the dirt and calling it 0 V, taping a sticky on the negative terminal of a battery that says "0 V", or poking an electrode up a rat's ass and calling that 0 V.

The utility that this assumption has is that it is pretty universal and can be applied to any problem, whether that problem involves batteries, or magnetic fields and moving conductors, or chemical reactions -- it's problem agnostic. It also makes it easier to "glue" disparate problems into a larger whole because they all use the same 0 V reference.

But even in physics, this definition is only applied where it is useful -- as soon as a more useful definition offers itself up for a particular problem, we almost always jump ship and use the same kind of 0 V definition that a high school student taking an electronics votech course would make.
 

WBahn

Joined Mar 31, 2012
29,863
Back in the 1950's the JIC attempted to define the symbols used today, and the Earth GND symbol shown in #11 was specifically defined as any conductor or circuit connected to earth GND.
Or any metallic part of a system that had contact with earth GND via a specific conductor or other definite means.
And, like the kibibyte, mibibyte, and gibibyte, the fact that they are officially defined in places like IEC 80000-13 and adopted by numerous national standards bodies, including NIST, and are therefore the terms that SHOULD be used, is largely irrelevant.

What matters is the terms that people ACTUALLY use and what they ACTUALLY mean by them. Trying to force an interpretation that is at odds with this, even if it is exactly in line with the official standards, it defeating the purpose of a standard in the first place, which is to foster common understanding and communication.

I'm certainly not saying I like that situation -- but it IS the reality with which we have to deal.

Consequently, the use of the term "ground" is going to always have multiple interpretations. Fortunately, in the vast majority of situations, the intended meaning is adequately clear from the context. When it's not -- and to the degree that it matters -- we need to seek clarification, and that clarification must be grounded, err... rooted, in what was meant, not the official definitions of the words that were used.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,777
When you say that the battery has become statically charged to 3 kV, that 3 kV is measured relative to what?
That's my point - relativity. Assuming ground to be zero volts is - well, read on please.
voltage, by it's very definition, is a potential difference between points, and on those values we will agree completely.
This I 100% agree with. It's a potential. As Mr. G my high school electronics teacher said "Voltage is akin to electric pressure." I understood that to mean it is a presence that remains like a bowling ball suspended in mid air by a string or rope. It WANTS to go somewhere (down) but it remains at its potential. Static. Unchanging. It goes nowhere until it goes somewhere. And energy, which is related, always moves from the higher potential to the lower potential. Once balanced there is no longer any movement (current in matters of electronics).
I don't think it's an assumption in the sense that we somehow "believe" it to be zero there and just can't prove it, but rather just an arbitrary definition that has no more or less validity that sticking a rod in the dirt and calling it 0 V
I agree with this as well. All I was saying in the other thread is that because; as @MaxHeadRoom often and clearly states is that people close to universally use the wrong term for grounding of a circuit. In the other thread I postulated the notion of using a different symbol for what people call ground. It's a half circle at the bottom of a line similar to all other ground symbols but with the circle instead of a rake, triangle or three tiered bars. The point of the proposed new symbol is to show an isolated - um - grounding point, or "Common" and eliminate the use of the term "Ground". Ground causes confusion. The introduction of a new symbol will likely cause even more confusion. But I'm sure with the introduction of any new term or symbol will always cause confusion until we grow custom to using it. The term that Peeves me is "Short". Almost universally used to describe every sort of electrical or electronic failure. Part of the time the correct term may be "Open", or some other term. I guess we all have Peeves.
Trying to force an interpretation that is at odds with this, even if it is exactly in line with the official standards, it defeating the purpose of a standard in the first place, which is to foster common understanding and communication.
Again, I just thought maybe a "Common" symbol without the term or indication of "Ground" may help to alleviate some of the confusion.

Here on AAC we've repeatedly met and welcomed new members who at first have used wrong terminology for components and circuit points. We teach them. Even I'm still learning. However, I find it interesting how much conversation this thread has already invoked. I didn't expect but a few more comments then to watch this thread begin collecting the dust of death. Or for this thread to ground to a halt. ")
 
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