Analog Electronic Modules
12-19
ET 200S Distributed I/O System
EWA-4NEB 780602402-12
Isolated sensors
The isolated sensors are not connected to the local ground potential. They can be
operated potential-free. Local conditions or interference can cause potential
differences U
CM
(static or dynamic) between the M-- measuring lines of the input
channels and the reference point of the measuring circuit M
ANA
.
The following applies to ensure that the approved value for U
CM
is not exceeded
during operation in areas with high EMC interference:
• with the 2AI U, 2AI I 4WIRE and 2AI TC analog input modules: Connect M--
with M
ANA
!
• There must not be a connection from M-- to M
ANA
when connecting 2-wire
measurement transducers for current measurement and resistor sensors.
Isolated sensors, continued
Figure 12-1 shows the general connection of isolated sensors to the isolated
analog input modules..
Isolated
sensors
M+
:
M
L+
M--
M
ANA
M+
:
M--
Backplane bus
ADC
Grounding busbar
U
ISO
Recommended
connection
U
CM
Central ground point
Logic
Figure 12-1 Connection of isolated sensors to an isolated analog input module.
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