Chapter 4 – Electrical Installation
Installation and Start-up Guide for NPBA-01
4-3
Earthing
The NPBA-01 module earth is internally connected to the rail onto
which the module is mounted. If the rail is fastened to an earthed
metallic assembly plate, the module is automatically earthed, and no
external earthing wire is needed. If the rail is fastened to a base that is
not earthed, the rail must be connected to the nearest earthing
terminal. However, the earthing wire should not be connected to the
same terminal as the power cable screens. (See Chapter 3, page 3-2.)
In the NPBA-01 module there are several built-in earthing terminals
(see Figure 4-3 below):
•
The PE terminal is internally connected to the NPBA-01 module
earth. Normally, no external wires need to be connected to this
terminal.
•
The SH terminal is internally connected to the NPBA-01 module
earth. The SH terminal is normally used for earthing the PROFIBUS
cable shield if there is no other station at which the cable shield is
connected directly to earth.
•
The SHF terminal is internally connected to the NPBA-01 module
earth via an RC filter. The SHF terminal is typically used for earthing
the PROFIBUS cable shield.
•
The DG terminal is isolated from the NPBA-01 module earth. This
terminal is used for connecting the third conductor of the bus cable.
The third conductor - Data Ground - offers a common reference or
comparison potential to all modules on the bus. The use of Data
Ground is highly recommended as it improves noise immunity.
Earthing the PROFIBUS
Cable Shields
The PROFIBUS cable shield may be connected straight to earth only at
one station. At other stations the cable shield should be earthed via an
RC filter (See Figure 4-3 below).
Figure 4-3 PROFIBUS bus cable connections.
SHF
D(P)
D(N)
NPBA-01
PROFIBUS
Master
SHF
D(P)
D(N)
NPBA-01
DG
DG
