Beijer Electronics X2 base 5 v2 Installation Manual page 25

Operator panel
RS422
PC
*
When a PC is connected to the operator panel, the internal 0 V (GND) of the
panel is connected to the protective ground via the PC.
A number of USB devices can have the shield connected together with the
protective ground. Here, the 0 V (GND) of the operator panel is connected to the
protective ground when, for example, a USB memory stick, keyboard, or similar
device is plugged in.
If a number of units are connected that have a 0 V and a ground connection, and
these are connected to various grounding points, there is a substantial risk of
problems. Grounding currents go through communication cables, the rear plate
of the controller, internally in the operator panel, and can cause errors.
Use external units to improve communication and achieve galvanic isolation.
Westermo has good industry-standard insulators that are also insulated from the
24 V DC feed.
Note:
It isvery import ant t o make sure t hat t he 24 V f eed in t he ext ernal insulat ion unit isnot
connect ed t o one of t he communicat ion out l et s. If it doesnot have 100%insulat ion
against t he 24 V f eed, dist urbancesand grounding current sf rom t he 0 V on t he 24 V
side disrupt t he communicat ion.
Using t hist ype of unit solvesone problem but creat es a larger problem! A subst andard
inst allat ion may work now, but problemsmay arise when ot her devices are connect ed.
Beij er Electronics, MAEN328
* RS232 * USB
*
Different ground potential
Additional Installation Tips
Modular controller
Power CPU COM COM2
* * *
*
= Internal 0 V (GND) connection
Printer
*
PC
*
25