Grounding Measures - Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual

Example: Installing an S7-300 with common potential modules
When using an SM 334 AI 4/AO 2 analog I/O module, connect one of the grounding
terminals M
The figure below shows an example of such a configuration: An S7-300 with common
potential modules
L1
N
PE
L+
M
external
24 V DC load power supply
4.9.5

Grounding measures

Bonding to ground
Low-impedance connections to ground reduce the risk of electric shock as a result of a
short-circuit or system fault. Low-impedance connections (large surface, large-surface
contact) reduce the effects of interference on the system or the emission of interference
signals. An effective shielding of cables and devices is also a significant contribution.
Warning
All protection class 1 devices, and all larger metal parts, must be bonded to protective
ground. That is the only way to safely protect operators from electrical shock. This also
discharges any interference transmitted from external power supply cables, signal cables or
cables to the I/O devices.
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
to the CPU's chassis ground.
analog
PS S7-300 CPU
L1
L+
M
N
M
Common grounding
line in the cabinet
4.9 Electrical assembly, protective measures and grounding
µ P
2
1 mm
4AI/2AO
D D
A A
M
analog
+ +
V
A
Configuring
U
internal
Data
M
internal
4-21