Endress+Hauser Proline Promag W 400 - Page 25

Proline Promag W 400 Electrical connection
Endress+Hauser 25
7.1.5 Shielding and grounding
Modbus
The shielding and grounding concept requires compliance with the following:
• Electromagnetic compatibility (EMC)
• Explosion protection
• Personal protection equipment
• National installation regulations and guidelines
• Observe cable specification →  21.
• Keep the stripped and twisted lengths of cable shield to the ground terminal as short as
possible.
• Seamless cable shielding.
Grounding of the cable shield
To comply with EMC requirements:
• Ensure the cable shield is grounded to the potential matching line at multiple points.
• Connect every local ground terminal to the potential matching line.
NOTICE
In systems without potential matching, the multiple grounding of the cable shield causes
mains frequency equalizing currents!
Damage to the bus cable shield.
‣
Only ground the bus cable shield to either the local ground or the protective ground at one
end.
PROFIBUS DP
Optimum electromagnetic compatibility (EMC) of the fieldbus system can only be guaranteed
if the system components and, in particular, the lines are shielded and the shield forms as
complete a cover as possible. A shield coverage of 90% is ideal.
• To ensure an optimum EMC protective effect, connect the shield as often as possible to the
reference ground.
• For reasons of explosion protection, you should refrain from grounding however.
To comply with both requirements, the fieldbus system allows three different types of
shielding:
• Shielding at both ends.
• Shielding at one end on the feed side with capacitance termination at the field device.
• Shielding at one end on the feed side.
Experience shows that the best results with regard to EMC are achieved in most cases in
installations with one-sided shielding on the feed side (without capacitance termination at
the field device). Appropriate measures with regard to input wiring must be taken to allow
unrestricted operation when EMC interference is present. These measures have been taken
into account for this device. Operation in the event of disturbance variables as per NAMUR
NE21 is thus guaranteed.
Where applicable, national installation regulations and guidelines must be observed during
the installation!