We
all know the ground design principles 1) systems must have a single point of ground
only, and 2) all ground paths must lead by a single path as directly back to this
single ground point as possible. However, any wire based data communication
circuit by their very nature violate both of these ground design principles.
First, they often connect 2 systems designs, installed, and maintained by different
vendors - and therefore short togather two subtly different ground designs.
Second, they always create a alternate path or ground loop within even a single
system. Surge energy always has the alternative of traveling through the entended
ground path - and/or traveling through the data comm wires.
Application note
#AN001 discusses this problem further, plus explains how gavlanic/optical isolation
provides a neat, invaluable solution. It also explains the concepts of partial
and full galvanic isolation - a critical concept in DC power systems. RobustDC
is perhaps the only company on earth to make fully isolated (3 of 3 ground isolation)
products for use with DC power supplies.
