Siemens SIMATIC ET 200S Manual page 24

Connecting
5.1 Connecting measuring sensors
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. These can
be potential-free. Depending on local conditions or interference, potential differences U
(static or dynamic) can occur between the measuring lines M- of the input channels and the
reference point of the measuring circuit M
In environments with a high level of EMC interference, it is advisable to connect M- to M
in order to prevent the permissible U
The following schematic representation illustrates the connection of isolated measuring
sensors to the analog input modules.
5
①
②
③
④
⑤
24
Measuring line (positive)
Measuring line (negative)
Analog measuring circuit reference potential
Ground connection
Rated load voltage 24 V DC
Potential difference between inputs
Potential difference between M- and central grounding point
mA
mA
4
Logic
Backplane bus
Ground bus
Central grounding point
Isolated measuring sensors
.
ANA
value from being exceeded.
CM
1
3
2AI I 4WIRE HS analog electronic module (6ES7134-4GB62-0AB0)
2
Manual, 01/2008, A5E01076124-02
CM
ANA