Analog electronic modules
4.3 Basics of Analog Value Processing
ET 200S
4-16 Manual, Edition 10/2005, A5E00514527-01
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
CM
(static or
dynamic) can occur between the measuring lines M- of the input channels and the reference
point of the measuring circuit M
ANA
.
To ensure that the permitted value for U
CM
is not exceeded in environments with strong EMC
interference, the following applies:
• In the case of the analog input modules 2AI U, 2AI I 4WIRE, and 2AI TC: Connect M-
with M
ANA
!
• When connecting two-wire measuring transducers for current measurement and when
connecting resistance-type sensors, you must not connect M- to M
ANA
.
The following figure illustrates the connection of isolated measuring sensors to the floating
analog input modules.
Connection of isolated measuring sensors to a floating analog input module:
1
2
3
4
5
6
0
0
/
0
0
$1$
0
0
$'8
8
,62
8
&0
(1) Logic
(2) Backplane bus
(3) Ground bus
(4) Central grounding point
(5) Recommended connection
(6) Isolated measuring sensors
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