Siemens SIMATIC S7-400 Reference Manual page 205

To ensure that the permissible value for U
affected environments, connect M- to MANA in modules with an M
1
3
Figure 5-5
(1)
(2)
(3)
M +:
M -:
M
ANA
U
ISO
Note
Do not connect M- to MANA when connecting 2-wire transducers for current measurement
and when connecting resistance-type sensors. This also applies to inputs which are
programmed accordingly, but remain unused.
Non-isolated sensors
The isolated sensors are not connected with the local ground potential (chassis ground). When
using non-isolated sensors, you must connect M
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
M+
M-
M+
M-
M
ANA
U
ISO
Connecting isolated sensors to an electrically isolated AI
Electrically isolated sensors
Chassis ground
Connection required for modules with M
Measuring line (positive)
Measuring line (negative)
: Reference potential of the analog measuring circuit
: Potential difference between M
5.9 Connecting sensors to analog inputs
is not exceeded during use in heavily EMC-
CM
2
ANA
and chassis ground
ANA
to chassis ground.
ANA
Analog modules
connection.
ANA
205