Rockwell Automation System Design for the Control of Electrical Noise - Manual (Page 44)

Publication GMC-RM001A-EN-P — July 2001
4-4 Shielding Wires, Cables, and Components
Ferrite Sleeve Limitations
After implementing all the guidelines presented in this manual, a
properly built system should perform well without ferrite sleeves.
However, by including sleeves in your installation, the system will
avoid problems caused during future modifications.
System installations can benefit from ferrite sleeves, but you should
also realize that ferrite sleeves alone are not a substitute for proper
noise coupling reduction techniques.
As a rule, include sleeves as standard to obtain the most effective
overall system.
For more information about ferrite sleeves, refer to Appendix B.
Mixing Categories It is often difficult to segregate effectively in a confined space. When
strict segregation isn’t practical, minimize overlap and cross cables at
right angles. Test results in Appendix A show that even a close parallel
run of 0.5 m (20.0 in.) will allow significant noise coupling (refer to
the section Wire Segregation Test Results).
You can convert wiring designated dirty or very-dirty to the next
lower category by means of shielding using either shielded cable or
conduit where required. Figure 4.5 and Figure 4.6 show how this
technique may be used to mix categories without breaking the
segregation rules.