Siemens Simatic S7-400 - Manual (Page 262)

Analog Modules
5-46
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
5.9 Connecting Voltage Sensors
Note
The necessary connecting cables, which result from the potential connection of the
analog input module and the sensors, are not drawn in the figures shown below.
In other words, you must continue to take note of and implement Section 5.8 with
its generally applicable information on connecting sensors.
Abbreviations and Mnemonics Used in the Figure Below
The abbreviations and mnemonics used in the figure below have the following
meanings:
M +: Measuring line (positive)
M –: Measuring line (negative)
M
ANA
: Reference potential of the analog measuring circuit
Connection of Voltage Sensors
+
–
U
+
–
U
M+
M–
M+
M
ANA*
M–
* Connection required in the case of modules with M
ANA
Figure 5-9 Connecting Voltage Sensors to an AI