Analog Modules
4-66
Programmable Logic Controllers S7-300 Module Data
A5E00105505-03
4.13 Connecting Loads/Actuators to analogo output
Introduction
You can use the analog output modules to supply loads and actuators with current
and voltage.
This section contains general information that is generally applicable to all the
connection options for loads and actuators described in the sections that follow.
Cables for analog signals
For the analog signals, you should use shielded and twisted pair cables. The cables
Q
V
and S+ and M and S–, respectively, are to be twisted together. This reduces the
interference. Ground the screen of the analog cables at both ends of the cables.
If there are potential differences between the cable ends, an equipotential bonding
current, which can flow over the shield, can cause interference of the analog
signals. In such a case, you should ground the shield at one end of the cable only.
Isolated Analog Output Modules
With the isolated analog output modules there is no electrical connection between
the reference point of the measuring circuit M
ANA
and the M terminal of the CPU.
You must use isolated analog output modules if a potential difference U
ISO
can
occur between the reference point of the measuring circuit M
ANA
and the
M terminal of the CPU. By means of a equipotential bonding conductor between
the M
ANA
terminal and the M terminal of the CPU, make sure that U
ISO
does not
exceed the permitted value.
Non-Isolated Analog Output Modules
With the non-isolated analog output modules, you must establish a connection
between the reference point of the measuring circuit M
ANA
and the M terminal of
the CPU. Therefore, connect the M
ANA
terminal with the M terminal of the CPU. A
potential difference between M
ANA
and the M terminal of the CPU can lead to a
corruption of the analog signal.
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