Table of Contents
Advertisement
5 Connecting to power supply
Safety instructions
Voltage supply
Connection cable
Cable gland ½ NPT
Cable screening and
grounding
20
5
Connecting to power supply
5.1
Preparing the connection
Always keep in mind the following safety instructions:
Warning:
Connect only in the complete absence of line voltage.
•
The electrical connection must only be carried out by trained
personnel authorised by the plant operator.
•
If overvoltage surges are expected, overvoltage arresters should
be installed.
The voltage supply is provided by a Profibus DP /PA segment coupler.
The voltage supply range can differ depending on the instrument
version. You can find the data for voltage supply 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 for instruments with housing and
cable gland. To ensure the seal effect of the cable gland (IP protection
rating), find out which cable outer diameter the cable gland is suitable
for.
Use a cable gland fitting the cable diameter.
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.
You can find detailed information of the cable specification, installa-
tion and topology in the "Profibus PA - User and Installation Guide-
line" on www.profibus.com.
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.
In systems with potential equalisation, connect the cable screen
directly to ground potential at the power supply unit, in the connection
box and at the sensor. The screen in the sensor must be connected
directly to the internal ground terminal. The ground terminal outside
on the housing must be connected to the potential equalisation (low
impedance).
In systems without potential equalisation, connect the cable screen
directly to ground potential at the power supply unit and at the sensor.
VEGASON 62 • Profibus PA
Advertisement
Table of Contents
