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IM483 Operating Instructions Revision R032306
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IM483 Operating Instructions Revision R032306
R e c o m m e n d e d W i r i n g
R u l e s o f W i r i n g a n d S h i e l d i n g
Noise is always present in a system that involves both high power and
small signal circuitry. Regardless of the power configuration used for your
system, there are some wiring and shielding rules that should be fol-
lowed to keep the noise-to-signal ratio as small as possible.
R u l e s o f W i r i n g
n
Power supply and motor wiring should be shielded twisted
pairs run separately from signal carrying wires.
n
A minimum of 1 twist per inch is recommended.
n
Motor wiring should be shielded twisted pairs using 20-
gauge wire or, for distance greater than 5 feet, 18 gauge or
better.
n
Power ground return should be as short as possible to estab-
lished ground.
n
Power supply wiring should be shielded twisted pairs. Use
18 gauge wire if load is less than 4 amps, or 16 gauge for
more than 4 amps.
n
Do not “Daisy-Chain” power wiring to system components.
R u l e s o f S h i e l d i n g
n
The shield must be tied to zero-signal reference potential.
In order for shielding to be effective, it is necessary for the
signal to be earthed or grounded.
n
Do not assume that earth ground is true earth ground. De-
pending on the distance to the main power cabinet, it may be
necessary to sink a ground rod at a critical location.
n
The shield must be connected so that shield currents drain
to signal-earth connections.
n
The number of separate shields required in a system is equal
to the number of independent signals being processed plus
one for each power entrance.
n
The shield should be tied to a single point to prevent ground loops.
n
A second shield can be used over the primary shield, how-
ever, the second shield is tied to ground at both ends.
R e c o m m e n d e d P o w e r S u p p l y C a b l e s
Power supply cables must not run parallel to logic level wiring as noise
will be coupled onto the logic signals from the power supply cables.
