Priniples of analog value processing
4.7 Connecting loads/actuators to analog outputs
S7-300 Automation System Module data
4-20 Manual, 08/2006, A5E00105505-04
4.7 4.7 Connecting loads/actuators to analog outputs
Connecting loads/actuators to analog outputs
The analog output modules can be used to supply power to loads and actuators.
Cables for analog signals
Always use shielded twisted-pair cables to wire analog signals. Form two twisted pairs of the
Q
V
and S+, and M and S- signals in order to reduce interference. Connect both ends of the
analog cable shield to ground.
Any potential difference between the cable ends may cause an equipotential current on the
shield, and thus disturbance on analog signals. To avoid this situation, you should ground
the shield only at one end of the cable.
Electrically isolated analog output modules
When using electrically isolated analog output modules, the reference point of measuring
circuit M
ANA
and the CPU's M terminal are not galvanically interconnected.
Always use electrically isolated analog input modules if there is a risk of a potential
difference V
iso
developing between the reference point of measuring circuit M
ANA
and the M
terminal of the CPU. Use an equipotential bonding conductor to interconnect the M
ANA
terminal and the M terminal of the CPU, in order to prevent V
iso
from exceeding the permitted
value.
Non-isolated analog output modules
When using on-isolated analog output modules, always interconnect the reference point
M
ANA
of the of measuring circuit with terminal M of the CPU. Wire the M
ANA
terminal to the M
terminal of the CPU. Any potential difference between M
ANA
and the M terminal of the CPU
could otherwise corrupt the analog signal.
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