Siemens S7-300 - Connection of the Load Voltage Reference Potential

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S7-300 Automation System, Hardware and Installation: CPU 312IFM - 318-2 DP
A5E00203919-01
5-27
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Numerous output modules require an additional load voltage for switching control
devices.
The table below shows how to connect the load voltage reference potential M
external
for the various configuration versions.
Table 5-9 Connection of the load voltage reference potential
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grounded Connect M
external
with M
on the CPU
Connect or do not connect
M
external
to the common
grounding line
-
ungrounded Connect M
external
with M
on the CPU
Connect or do not connect
M
external
to the common
grounding line
ungrounded operation
of CPU 312 IFM is not
possible