Siemens SIMATIC ET 200S Manual page 20

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 encoders
The isolated measuring encoders 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
encoders to the analog input modules.
5
①
②
③
④
⑤
20
Measuring line (positive)
Measuring line (negative)
Analog measuring circuit reference potential
Ground connection
Rated load voltage 24 V DC
Potential difference between inputs and reference potential of the measuring
circuit M
ANA
Potential difference between M
4
Logic
Backplane bus
Ground bus
Central grounding point
Isolated measuring encoders
and central grounding point
ANA
.
ANA
value from being exceeded.
CM
1
3
2AI I 4WIRE ST analog electronic module (6ES7134-4GB11-0AB0)
2
Manual, 04/2007, A5E01076100-01
CM
ANA