The term ground and common are frequently mixed up and interchanged.
One does not necessarily mean the other.
There are two schools of thought, some specify complete isolation, i.e. all systems and power supplies kept separate by isolation.
The other where all components of a system, including all metalic objects/enclosures power supplies, shields, are connected to an earth point, common to service ground etc.
This is called uni-potential bond/grounding.
Once a method is selected, it should be carried out in the correct manner, many problems occur because one method or the other is not adhered to completely or correctly.
I prefer the latter because it is usually easier to achieve.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.