Author Topic: A talk on protective Ground, signal return and "0V"  (Read 1168 times)

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Offline Terry Bites

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A talk on protective Ground, signal return and "0V"
« on: February 07, 2021, 05:56:49 pm »
I thought it would be a good idea have a talk on protective ground, signal return and "0V" they are clearly not the same thing but they are so often treated as if they are.
 

Offline IamSynthetiC

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Re: A talk on protective Ground, signal return and "0V"
« Reply #1 on: February 07, 2021, 10:43:41 pm »
From my undertanding they all have different context.
0V is either ,the usual GND in DC applications, or 0V Potential in AC applications.
Protective GND is usually refered to a GND setup that protects a person or a device ie. ESD protection
Now for Signal return i dont know. After a quick googling though i can tell you, that Signal Return is an automotive term for "GND" but as the articles below says, there is no real GND on a car and the term is there to differentiate.
https://link.springer.com/chapter/10.1007%2F978-1-4020-7783-8_3
 

Offline Brumby

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Re: A talk on protective Ground, signal return and "0V"
« Reply #2 on: February 09, 2021, 09:40:10 am »
... but as the articles below says, there is no real GND on a car and the term is there to differentiate.
Many automotive EMC problems are attributed to “bad ground” connections. Bad ground seems to be the cause of many problems in all types of electrical circuits. The reason that there are bad ground connections is simple. There is not a “ground” anywhere on a vehicle! The reason there is no ground connection is also simple. The vehicle is intended to travel on the ground, not attached to it.

This is actually quite wrong - or, at least, extremely misleading.

The term "ground" is quite arbitrary and - in practice - refers to any sufficiently large body that has a consistent electrical potential across its extents, within which an electrical system is found.  As such, the car's body can be considered as a ground - quite validly.  This is not to mention the fact that the references it decries are still very pertinent in problem solving.  It is also true that the car's body is commonly used as the signal return (but not always!) - and it is usual for it to be given the honour of the 0V reference.  While that last one is entirely arbitrary, it's an easy choice.

People get too wound up with the pedantic application of the term to the big lump of dirt we stand on.   (Which, by the way, ONLY has any effectiveness because we bury big conductors in it and attach cables to them.)

For anyone who wants to argue this - just go away.  Please ... just find another thread.


Discussion on the original point is, however, quite worth having.....
  • protective ground
  • signal return
  • "0V"
they are clearly not the same thing but they are so often treated as if they are.
These are, indeed, three separate functions within a circuit - and it is quite feasible that they are three separate connections - but, in practice, using the same connection for all three has proven to be fairly effective in a wide range of circuits.  It is this widespread usage that has led to the lines being blurred, especially to those who have limited experience.
« Last Edit: February 09, 2021, 09:42:24 am by Brumby »
 

Offline S. Petrukhin

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Re: A talk on protective Ground, signal return and "0V"
« Reply #3 on: February 10, 2021, 11:55:16 am »
Personally, I have established a rule for myself to consider each body (device) as a separate potential. I always use flying lines with galvanic isolation to connect devices. At the same time, I connect the protective screen only on one side.

I assumed that it would be good to connect the protective shield on both sides via a resistor and a capacitor to the PE.
The case of the loss of the PE and the occurrence of a potential on the PE made me abandon this.  :)
Even in industrial devices, there is a loss of PE and the appearance of a strong potential on it, which can lead to smoke in the cable.  :-//

And sorry for my English.
 


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