Siemens 505-2557 Manual De Usuario

 

Installation

Ground at One End Only

Siemens Energy & Automation, Inc. recommends that all signal wires be
shielded twisted–pair with a foil wrap shield and a separate drain wire and
that they be installed in a metallic conduit. Use Belden cable 8761 or
equivalent which contains foil wrap shield and a separate drain wire. The
shield and the foil wrap should be twisted together and should be
terminated at only one end. The other end should be left in an open circuit
condition. Siemens recommends that the shield be terminated at the PLC
end of the signal wire. Special components are installed on the module to
aid in the rejection of noise.

When entering the industrial cabinet the shield wires should be routed from
the main terminal strip all the way to the PLC. Signal leads that do not
maintain a shield from the terminal strip to the PLC act as antennas and
are susceptible to radiated and conducted emissions in the cabinet.
Unprotected cables may introduce measurement errors in the module.

The fron connector on the module contains a G terminal which may be used
for the shield wire if the installation is in a noise free environment. If the
installation is in an extremely noisy environment Siemens strongly
recommends that the shield wires be terminated to the PLC chassis ground.

This product has been exhaustively tested to maximize its ability to reject
noise from inductive sources as well as showering arcs, fast transients and
other high frequency generators and has determined that the best
performance results from connecting all shield wires together at the PLC
module and terminating this single wire to the chassis ground with a large
current capacity conductor. The PLC chassis should then be wired to earth
ground with a large current capacity conductor. Siemens recommends using
a #8 gauge wire from the PLC chassis to the earth ground connection.