User manual

Connecting the inputs
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Safety measures with analog signals
XUse shielded twisted pair cables to prevent interference
with the analog signals.
XFor short cable lengths, ground the shield at both ends
using a large contact area. If the cable length exceeds 30 m
or so, grounding at both ends can result in equalization
currents between the two grounding points and thus in the
interference of analog signals. In this case, only ground the
cable at one end.
XDo not lay signal lines parallel to power cables.
XConnect inductive loads to be switched via the EZ outputs
to a separate power feed, or use a suppressor circuit for
motors and valves. If loads such as motors, solenoid valves
or contactors are operated with EZ via the same power
feed, switching may result in interference on the analog
input signals.
The following four circuits contain examples of applications for
analog value processing.
Caution!
Analog signals are more sensitive to interference than
digital signals. Consequently, greater care must be taken
when laying and connecting the signal lines.
Incorrect switching states may occur if they are not
connected correctly.
Caution!
Ensure that the reference potential is connected. Connect
the 0 V of the power supply unit for the different setpoint
potentiometers and sensors shown in the examples to the
0 V and neutral conductor terminal (EZ-AB) of the EZ power
feed. Otherwise incorrect switching states may occur if they
are not connected correctly.
EZ500_700.book Page 45 Tuesday, May 3, 2005 5:15 PM