... 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.