Siemens Simatic S7-300

Priniples of analog value processing
4.2 Wiring transducers to analog inputs
S7-300 Automation System Module data
Manual, 08/2006, A5E00105505-04
4-3
4.2.1 Wiring electrically isolated transducers
Electrically isolated transducers
Electrically isolated sensors are not connected to local ground potential (local ground.) They
can be operated in electrically isolated mode.
Potential differences may develop between electrically isolated sensors. Those potential
differences may be caused by distrubance, or may develop as a result of the local
distribution of transducers.
In environments with a high level of EMC interference, it is advisable to interconnect M- with
M
ANA
in order to prevent the permissible CMV value from being exceeded.
Note
With modules where V
CM
≤ 2.5 V, you have to connect M- and M
ANA
(see following
diagrams).
Wiring electrically isolated transducer to electrically isolated AI
The CPU / IM 153 can be operated in grounded mode or ungrounded mode.
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Figure 4-1 Wiring electrically isolated transducers to electrically isolated AI