Siemens S5-135U/155U appendix Shielding and Grounding

Installation Guidelines

In these cases, double-shielded coaxial cables (triaxial cables) must be used to transmit the video signals. The inner braided shield of the coaxial cable serves as the return conductor and must not be connected to the shield bar. The outer braided shield provides a path to ground for interference currents and must be incorporated in the shielding and grounding measures.

To avoid ground loops, the electronics ground and housing ground of the monitor must be independent. This requirement is met when:

SThe electronics and housing grounds of the monitor are metallically isolated,

Sor the electronics and housing grounds are connected via a voltage-dependent resistor (VDR) fitted by the manufacturer of the monitor.

3.6.2Shielding and Grounding

If the monitor and PLC are used under harsh industrial conditions, you must ensure the following at the PLC end:

SCables shields should be connected to the shield bar in the cabinet, immediately after the cable inlet;

-the video cables should be fully stripped;

-the outer braided shield should be secured to the shield bar of the PLC over as large an area as possible (e.g. with metal ties which enclose the shield or with cable clamps).

SShield bars should be connected to the frame or cabinet panel over a large area.

SShield bars should be connected to the ground point of the cabinet.

You must ensure the following at the monitor end:

SSeparate the electronics ground and housing ground.

-Remove the jumper at the monitor to separate the two grounds.

-Fit touch protection at the video sockets because hazardous touch voltages of more than 40 V may be present at the sockets after separation of the grounds.

SConnect the ground clamp of the monitor to the protective conductor.

SConnect the cable shields to the ground clamp of the monitor;

-fully strip the video cables;

-secure the outer braided shield to the ground clamp of the monitor over a large area.

System Manual	3-31
C79000-G8576-C199-06