Earth ground for simple DC circuit

Wendy

Joined Mar 24, 2008
23,415
Which pretty much is the definition of ambiguous. You would be hard pressed to find a schematic of a battery operated equipment without the ground symbol. They exist, but are rare.
 

CDRIVE

Joined Jul 1, 2008
2,219
I've attached a gif of an early Morse Telegraph circuit. I'm not certain where I got it from but looking at the way it was drawn (really nice, old timee, graphics) it leads me to believe that this was drawn not much later than the introduction of the Telegraph itself. Modern standards would classify this circuit to be more a "pictorial" than a schematic but I would bet that when this was drawn electrical & electronics standards were sparse and more Representative of real world objects. All that aside I was fascinated at it's depiction of earth ground. While it's not a schematic symbol of earth ground it does have an uncanny resemblance to it.
 

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GetDeviceInfo

Joined Jun 7, 2009
2,192
Which pretty much is the definition of ambiguous. You would be hard pressed to find a schematic of a battery operated equipment without the ground symbol. They exist, but are rare.
what is not uncommon in DC circuits is the chassis symbol. Not intended to indicate a ground connection.

The problem with Wikipedia is that it tries to be all to all. It even suggests that neutral be included in the ground definition.

but I would bet that when this was drawn electrical & electronics standards were sparse and more Representative of real world objects. All that aside I was fascinated at it's depiction of earth ground. While it's not a schematic symbol of earth ground it does have an uncanny resemblance to it.
as you can see, the 'ground' symbol's origins. The 'pitchfork' is a misnomer.
 

BillB3857

Joined Feb 28, 2009
2,570
I always envisioned the pitchfork as a line leading to a bus with additional lines buried in parallel. Similar to a radial grounding of an antenna mast, except in parallel.
 

Wendy

Joined Mar 24, 2008
23,415
So what reference would you accept? It is what I learned in college, and it has held true through my 30+ year carrier in Collin's Radio, Rockwell International, and Alcatel.

My symbol of choice has always been this...



It is extremely common in the vast majority of schematics.

My definition (which I wrote before looking at Wikipedia) and Wikipedia's don't meet your approval? That's OK, but it isn't your choice. It is the standard.

So here is another, not that it will convince...

http://www.thefreedictionary.com/ground

12. Electricity a. A large conducting body, such as the earth or an electric circuit connected to the earth, used as an arbitrary zero of potential.
b. A conducting object, such as a wire, that is connected to such a position of zero potential.
Looks like my two definitions there.

Like I said, there is more than one definition. I've quoted 3 sources, myself, and two online encyclopedia's. The Electrical Code is for high voltage line transmission standards, but it isn't related to electronic definitions.
 

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Thread Starter

Lightfire

Joined Oct 5, 2010
690
Hello,

I am very sorry for not replying. ;)

Um, my choice is what Bill's choice too. I just put the ground that I have put in my schematic because it is the only avaliable ground symbol in TinyCad (the software i am using for drwaing shcmeatic. )

THANKS!!!!!!!!!!!11
 

CDRIVE

Joined Jul 1, 2008
2,219
Kind of looks like pictures of a grassy field.
Stare at it for a while. You'll notice how the bottoms taper to a near point just like chassis ground. If that doesn't work for ya have a couple of stiff ones and look again. :D Actually it's beginning to look a lot like my "Lazy Z" bar napkin ground!:rolleyes: Speaking of which... I'm out here for now.
 

GetDeviceInfo

Joined Jun 7, 2009
2,192
You know Bill, what you use is your preference. Personally, I use a +v or a -v in digital/analog, but in electrical I use a two line drawing (or more for multiphase), along with the earth symbol as required, only because others depend on the drawings. All one has to do is look through the 'grounded' references in this forum to understand the ambiguity that exists with the term. There is no reason such a simple reference should create any confusion.

I will extend an apology to Lightfire for one of my posts in another thread referencing an audio track, as after doing some searching through posts, his confusion is justified.
 

GetDeviceInfo

Joined Jun 7, 2009
2,192
So what reference would you accept? It is what I learned in college, and it has held true through my 30+ year carrier in Collin's Radio, Rockwell International, and Alcatel.

My symbol of choice has always been this...



It is extremely common in the vast majority of schematics.

My definition (which I wrote before looking at Wikipedia) and Wikipedia's don't meet your approval? That's OK, but it isn't your choice. It is the standard.

So here is another, not that it will convince...

http://www.thefreedictionary.com/ground

Looks like my two definitions there.

Like I said, there is more than one definition. I've quoted 3 sources, myself, and two online encyclopedia's. The Electrical Code is for high voltage line transmission standards, but it isn't related to electronic definitions.
I totally support your case that this symbol is 'ground'. I've not indicated otherwise. I don't support the idea tha Wikipedia is the 'standard', although I'm sure they'd like to be known as such.
 

Wendy

Joined Mar 24, 2008
23,415
I find I disagree with Wikipedia myself now and again. I was surprised to find there are few other references out there. Something worth noting.
 

strantor

Joined Oct 3, 2010
6,782
I don't have 30+ years of experience or a college degree but I've been through copious training and pored over electrical schematics from all over the world and have come to the realization (generalization) that what lightfire drew is chasis ground. You will see this on machine/automobile prints where something is connected to a metal chasis. The "upside down christmas tree" is meant to be earth ground in an AC circuit, but turns out to be a catchall used for everything else. So it is important to note the difference between the 2 because in a chasis ground system the chasis is actually used as a normal current path and in some circuits often a ground is drawn just for the sake of drawing it and isn't actually a current path - or - is only a current path if something goes wrong.
 

strantor

Joined Oct 3, 2010
6,782
It's like a given that a ground has to be in a circuit. Simulation programs won't even let you run unless you put that stupid triangle (at least the triangle is more accurate than the christmas tree symbol) somewhere. Not every circuit needs a ground or common drawn in, as no such ground or common exists, but we feel compelled to draw it anyways.
 

Wendy

Joined Mar 24, 2008
23,415
The answer is not complex. It is what we've been talking about, the point by which all other voltages are measured, nothing more. It this circuit there is only one voltage, but that little ground symbol also defines polarity of the voltage.

In short, there is nothing wrong with it, it is the convention.
 

t06afre

Joined May 11, 2009
5,934
Here is the grounding symbols recognized by IEC. The PDF file is a cut out from IEC 60417-1 GRAPHICAL SYMBOLS FOR USE ON EQUIPMENT
A note then working with electrical simulators. You will need to define at least one point that is used as a reference point. All voltage values will be referenced to this point. And the same will also apply to electrical schematics. You are telling the reader that this is the reference point in your system.
 

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GetDeviceInfo

Joined Jun 7, 2009
2,192
The answer is not complex. It is what we've been talking about, the point by which all other voltages are measured, nothing more. It this circuit there is only one voltage, but that little ground symbol also defines polarity of the voltage.

In short, there is nothing wrong with it, it is the convention.
Actually Bill, it is more, it explicitly implies tied to earth.

The question of 'why', then is left unanswered, however, according to code, if it's 50vdc or greater, it must be tied to earth, and if it's less than 50vdc, it 'may' be tied to earth. There is a very important distinction going on here that should be acknowledged somewhere along the line.

you must also be aware, that polarity is not implied by the symbol.
 
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