Impulse 3089 - Manual (Page 17)

Appendix D - Ground Loop Phenomenon
Sealevel Systems ULTRA-SIO Page 14
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-SIO in a RS-485 network, care should be taken that both ends of the network are not
isolated from ground (see Figure 12). 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.
A B
Isolation
Barrier
DATA+
DATA-
Ground
Isolated
Ultra SIO
Non
Isolated
Ultra SIO
Figure 11 - Ultra-SIO cabling example