Siemens SIMATIC S5 Manual page 12

Standard Function Counter
Cable connection conditions
To ensure the correct functioning of the IP 265, there are important rules to be observed concerning
wiring and shielding. Since the IP 265 can only be used in conjunction with the S5-100U, S5-
90/95U or ET 200, it is assumed that you possess one of the relevant manuals. In the manual you
will find details of all cable connection conditions for programmable controllers (PLCs).
The following information refers only to the shielding of the connection cable.
Notes on cable shielding
Both ends of shielded cables should have a good electrical connection to the cabinet's chassis
ground. You can effectively suppress interference of all coupled frequencies only if the cables are
shielded at both ends. The shield should reach the module and should also be connected to the
module!
Note
There can be a compensating current flowing across cables shielded at both ends if
there are ground potential fluctuations. You should therefore join the connected
components with an additional equipotential bonding cable.
With SIMATIC controllers, the interference current on cable shielding is discharged to ground both
via the shielding rail and the equipotential bonding cable. To prevent these discharged currents from
becoming a source of interference, ground them on a low-resistance path as follows:
• Tighten the hold-down screws on the cable connectors, modules, and equipotential bonding
cables.
• Protect the contact surfaces of equipotential bonding cables against corrosion.
EWA 4NEB 812 6131-02
Installation Guidelines
2-3