Specifications

Table Of Contents
ARCnet156
33
6.5 Cable Shields
Connect the shields as shown in Figure 23. The shields should be connected at each module’s shield
connection terminal.
Do not ground the shield to earth ground or to the module’s power ground. The PROT485 and the
individual modules allow the shield to float a limited amount so that there are no ground loops. But if
the voltage on the shield becomes too great relative to the earth ground, then the excess voltage is
bled off with protective devices on the PROT485 or on the modules.
Figure 23 Using shielded cable
6.6 Noise
Do not run AC power wires or the module’s relay output wires next to the communication wires or
sensor input wires.
Table 21 lists common sources of noise that can affect signal quality. Try to avoid these sources of
noise when running communication or sensor wiring. If noise is a problem and it is not possible to
move the wiring, use ferrite clamp-on chokes on the cabling to help improve signal quality.
Table 21 Sources of noise
Spark ignitors Induction heaters
Radio transmitters Relays
Variable speed drives Fluorescent lights
Electric motors (> 1hp) Lamp dimmers
Generators Video display devices
Large contactors (i.e., motor starters) Parallel runs with power lines
Transformers Other electronic modules
Shield