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© Sealevel Systems, Inc. 2104 Manual | SL9092 9/2021
Appendix D
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Ground Loop Phenomenon
What is Ground Loop?
Ground loop Phenomenon occurs when two (or more) pieces of equipment are connected 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
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.
Figure 4 - 485I cabling sample
A
B
Isolation
Barrier
DATA+
DATA-
Ground
Isolated
Adapter
Non
Isolated
Adapter
