Omega Vehicle Security ISA RS-422 manual Appendix D Ground Loop Phenomenon, What is Ground Loop?

Appendix D - Ground Loop Phenomenon

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 OMG-ULTRA-SIOin 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.

Isolation

Barrier

A

Isolated

Ultra SIO

DATA+

DATA-

Ground

B

Non

Isolated

Ultra SIO

Figure 11 - OMG-ULTRA-SIOcabling example

OMG-ULTRA-SIO Page 16