Instruction Manual

Appendix C - Electrical InterfaceGround Loop Phenomenon
Sealevel Systems SeaLINK+485I Page 13
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 extreme cases
ground current can cause equipment malfunction or even destruction.
Cabling Recommendations
When connecting the SeaLINK+485I in an RS-485 network, care should be
taken that both ends of the network are not isolated from ground (see Figure 4).
This “floating” ground condition could cause 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.
AB
Isolation
Barrier
DATA+
DATA-
Ground
Isolated
Adapter
Non
Isolated
Adapter
Figure 4 – SeaLINK+485I cabling example