ABB S800 I/O User Manual page 51

In the event that the above recommendations (because of measurement techniques
or safety regulations) cannot be complied with, be sure to use these methods:
• Signal isolation for analog input signals
• Digital inputs and outputs are divided into groups at the MTUs and I/O
modules, with supply voltage distribution and grounding common for each
single groups.
Local grounding of a signal at the transducer location may be a requirement for
individual voltage supply to each transducer. This normally hinders the use of
MTUs for voltage distribution. A ground bar with the terminal block and fuse
equipment required by the application can be used in such cases.
If the transmitter/transducer has galvanic isolation of the supply, its signal zero can
be grounded where most suitable for measurement accuracy.
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When planning for the cable routing in the plant and when selecting suitable cables
to be used, the following should be considered:
• Routing of communication cables with regard to a.c. power wiring.
• Mixing of signals and signal types within cables.
• Need of shielded or un-shielded cables.
Cable entry into cabinets is generally from the bottom. Alternative cable entrances
can be accommodated if required. Refer to
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for details.
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