Analog Electronic Modules
12-43
Distributed I/O System ET 200S
EWA 4NEB 780 6024-02 07
Note
For the analog input modules 2AI U, 2AI RTD, and 2AI TC, you must short-circuit
unused analog inputs.
Abbreviations Used
The meanings of the abbreviations in the figures below are as follows:
M +: Measuring line (positive)
M –: Measuring line (negative)
M
ANA
: Reference potential of the analog measuring circuit
M: Frame connection
L +: Rated load voltage 24 VDC
U
CM
: Potential difference between inputs and reference potential
of the measuring circuit M
ANA
U
ISO
: Potential difference between M
ANA
and the central grounding point
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– to 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
.
To Next Page
Loading...
