Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 419)

Section
7C
7C-1
Noise Prevention
This section discusses wiring guide lines and techniques that should be
followed to help lower system noise susceptibly. Of these guide lines are
followed, noise should not be a factor in most 9/Series system applications.
The first measures to take to protect the electrical system from electrical
noise is to provide a protective ground. Proper grounding helps reduce the
effects of electrical noise by isolating induced noise voltages to individual
ground wires and shunting them to ground. This allows the noise to be
directed to the earth instead of being transmitted through the cables. See
page 3B-9 (9/230 systems), page 4D-10 (9/260 and 9/290 systems), or
page 5A-42 (9/440 systems) for details on proper protective grounding.
In addition to protective grounding, the following noise prevention
measures may also be used:
Signal Grounding
Mechanical Shielding
Shielded Cables and Twisted-pair Cables
Separation of Cable Routes
Noise Suppressors
To prevent noise related problems, first find the noise transmission route
and then take the appropriate noise prevention measures.
Signal Grounding
Signal grounding is used to direct any electrical noise, caused by shorted or
leaking high frequency electrical currents, to earth ground. Protective
ground, which has a high impedance path for high frequency noise, cannot
effectively lead electrical noise from high frequency current to the earth
ground.
Signal grounding must be made separately from other protective electronic
component grounding. Protective ground and signal ground methods differ
from each other in that the type of grounding wire used is different.
Signal noise, which is caused by high frequency current, has strong skin
effect and flows only on the surface layer of the grounding wire.
Therefore, the wire used for signal grounding should be as thick as
possible and as short as possible to minimize resistance and inductance.
7C.0
Section Overview
7C.1
Preventing Noise