Siemens Simatic RF300 System Manual page 121

4.5.8 Cable shielding
Signal cables must be shielded in order to prevent coupling of interference.
The best shielding is achieved by installing the cables in steel tubes. However, this is only
necessary if the signal cable is routed through an environment prone to particular
interference. It is usually adequate to use cables with braided shields. In either case,
however, correct connection is vital for effective shielding.
Note
An unconnected or incorrectly connected shield has no shielding effect.
As a rule:
● For analog signal cables, the shield should be connected at one end on the receiver side
● For digital signals, the shield should be connected to the enclosure at both ends
● Since interference signals are frequently within the HF range (> 10 kHz), a large-area HF-
proof shield contact is necessary
Figure 4-18
The shielding bus should be connected to the control cabinet enclosure in a manner allowing
good conductance (large-area contact) and must be situated as close as possible to the
cable inlet. The cable insulation must be removed and the cable clamped to the shielding
bus (high-frequency clamp) or secured using cable ties. Care should be taken to ensure that
the connection allows good conductance.
SIMATIC RF300
System Manual, 07/2017, C79000-G8976-C345-07
Cable shielding
4.5 Guidelines for electromagnetic compatibility (EMC)
Planning the RF300 system
121