S7-300 Configuration With Floating Reference Potential (Cpu 313 - 318-2 Dp) - Siemens SIMATIC S7-300 Hardware And Installation Manual

Ground bus
Figure 5-9 S7-300 configuration with floating reference potential (CPU 313 – 318-2 DP)
If the jumper is not installed, the reference potential of the S7-300 is connected
internally to the ground conductor via an RC system and the rail. This discharges
radio-frequency interference current and avoids static charge.
To create a floating reference potential, remove the jumper from the CPU
between the M terminals and functional ground.
S7-300 Programmable Controller Hardware and Installation
A5E00105492-02
M
M
L +
L +
M
M
1M <100 nF
Grounded CPU connection
Profile rail
Configuring
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