Analog Electronic Modules
12-45
Distributed I/O System ET 200S
EWA 4NEB 780 6024-02 07
Non-Isolated Measuring Sensors
The non-isolated measuring sensors are connected to the local ground potential.
You must connect M
ANA
to the ground potential. Depending on local conditions or
interference, potential differences U
CM
(static or dynamic) can occur between the
locally distributed measuring points.
If the permitted value for U
CM
is exceeded, there must be equalizing lines between
the measuring points.
Figure 12-2 illustrates the connection of non-isolated measuring sensors to a
floating analog input module.
Non-isolated
measuring
sensors
M+
M
L+
M–
M
ANA
M+
M–
Backplane bus
U
CM
ADC
Ground bus
U
ISO
Logic circuitry
Potential
equalizing line
Figure 12-2 Connection of Non-Isolated Measuring Sensors to a Floating Analog Input
Module
Operating Four-wire Measuring Transducers on an External Voltage Supply
If there is isolation between the output and the supply of the measuring transducer,
you can connect it to the 2AI I 4WIRE without additional connections.
If there is no isolation between the output and the supply of the measuring
transducer, you can connect it to the 2AI I 4WIRE only if the reference potential of
the power supply voltages (24 VDC) is the same.
If there is an increase in interference radiation, a connection between M– and M
ana
on the terminal module of the 2AI I 4WIRE is recommended.
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