Siemens ET 200S Manual page 399

Note
For the analog input modules 2AI U, 2AI RTD, and 2AI TC, you must short-circuit
unused analog inputs.
Abbreviations Used
The meanings of the abbreviations in the figures below are as follows:
M +:
M –:
M :
ANA
M:
L +:
U :
CM
U :
ISO
Isolated Measuring Sensors
The isolated measuring sensors are not connected to the local ground potential.
They can be floating. Depending on local conditions or interference, potential
differences U
the input channels and the reference point of the measuring circuit M
To ensure that the permitted value for U
strong EMC interference, the following applies:
S In the case of the analog input modules 2AI U, 2AI I 4WIRE, and 2AI TC:
Connect M– to M
S When connecting two-wire measuring transducers for current measurement and
when connecting resistance-type sensors, you must not connect M– to M
Distributed I/O System ET 200S
EWA 4NEB 780 6024-02 07
Measuring line (positive)
Measuring line (negative)
Reference potential of the analog measuring circuit
Frame connection
Rated load voltage 24 VDC
Potential difference between inputs and reference potential
of the measuring circuit M
Potential difference between M
(static or dynamic) can occur between the measuring lines M– of
CM
.
ANA
Analog Electronic Modules
ANA
and the central grounding point
ANA
is not exceeded in environments with
CM
.
ANA
.
ANA
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