VEGA VEGABAR 61 Profibus PA - Manual (Page 17)

5 Connecting to power supply
5.1 Preparing the connection
Always keep in mind the following safety instructions:
l Connect only in the complete absence of line voltage
l If overvoltage surges are expected, overvoltage arresters should
be installed according to Profibus specifications
Tip:
We recommend VEGA overvoltage arrester B63-32.
In hazardous areas you should take note of the appropriate
regulations, conformity and type approval certificates of the sensors
and power supply units.
Power is supplied via a Profibus DP/PA segment coupler or a
VEGALOG
571 EP input card. The power supply range can differ
depending on the instrument version.
The data for power supply are specified in chapter "Technical data".
Connection is made with screened cable according to the Profibus
specification. Power supply and digital bus signal are carried over the
same two-wire connection cable.
Use cable with round cross-section. A cable outer diameter of 5 … 9 mm
(0.2 … 0.35 in) ensures the seal effect of the cable gland. If you are
using cable with a different diameter or cross-section, exchange the
seal or use a suitable cable gland.
Please make sure that your installation is carried out according to the
Profibus specification. In particular, make sure that the termination of
the bus is done with appropriate terminating resistors.
On the instrument with cable entry ½ NPT and plastic housing there is
a metallic ½" threaded insert moulded into the plastic housing.
Caution:
No grease should be used when screwing the NPT cable gland or
steel tube into the threaded insert. Standard grease can contain
additives that corrode the connection between threaded insert and
housing. This would influence the stability of the connection and the
tightness of the housing.
Note safety instructions
Take note of
safety instruc-
tions for Ex ap-
plications
Select power supply
Selecting connection
cable
Cable gland ½ NPT
VEGABAR 61 • Profibus PA 17
5 Connecting to power supply
28251
-
EN
-081209