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MINT – IO
REF NO: m25A/om/101
Issue No: 11
The drawback of the three conductor option is elevated cable pricing and is
slightly more difficult to install. Care must also be taking using this option not
to create a ground loop
.
Note:
Ground on IO module is Pin 30 at 24V Power supply connector which is
0V or “-“V
.
Good installation practice for RS485 systems:
Use isolated power supplies to ensure that the IO modules are not
earthed. Only one module on the network should be earthed. (Module1).
Use RS485 shielded twisted cable to prevent electrical noise pickup.
Use a ground wire to connect all of the 0V terminals on the modules
together. This will ensure that all of the modules are at the same potential.
The ground wire must be earthed at Module1 only.
Use a screened cable to prevent electrical noise pickup. This screen must
be earthed at one end only, Module1. If a ground wire is not available then
the screen can be used instead. To get the best performance this is not
recommended.
The RS485 and power supply is wired correctly.
Do not carry RS485 and 24V DC power supply in same cables.
Use Separate isolated 24V DC for RS485 devices power supply and field
inputs.
The 0V of the power supply must be earthed.
The screen of the RS485 cable must be earthed.
The RS485 devices must be at the same earth potential.
