Appendixd - Ground Loop Phenomenon; What Is Ground Loop; Cabling Recommendations; Figure 8 - Iso Comm +2 Cabling Example - SeaLevel ULTRA COMM+I.PCI 3055 User Manual

Appendix D - Ground Loop Phenomenon

What is Ground Loop?

Ground loop Phenomenon occurs when two (or more) pieces of equipment are
connected together with a common ground and a different ground potential
exists at each location. This current can cause the connected equipment to
experience noise that in turn causes data transmission errors. In the extreme this
ground current can cause equipment malfunction or even destruction.

Cabling Recommendations

When connecting the ULTRA COMM+I.PCI in a RS-485 network, care should
be taken that both ends of the network are not isolated from ground (see Figure
8). This "floating" ground condition could cause the capacitive or inductive
coupling of voltages that will cause a break down in the DC to DC converter
circuit or in the opto-isolator circuit. This condition will cause data errors and
possibly destruction of the receiver circuit.
Isolated
Adapter
Isolation
Barrier
Figure 8 – ULTRA COMM+I.PCI cabling example
Sealevel Systems ULTRA COMM+I.PCI
Appendix D - Asynchronous Communications
A
DATA+
DATA-
Ground
B
Non
Isolated
Adapter
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