VEGA VEGAFLEX 66 (-110…+400°C) Foundation Fieldbus - Manual (Page 18)

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 Foundation Fieldbus
specification
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.
The instrument requires a supply voltage of 9 … 32 V DC.
Power and the digital bus signal are carried on the same two-
wire connection cable. Power is supplied via the H1 power
supply.
Connection is carried out with screened cable according to
Fieldbus specification.
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 other diameter or cross-
section, you have to exchange the seal or use a suitable cable
gland.
Make sure that the entire installation is carried out according to
the Fieldbus 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
18 VEGAFLEX 66 • Foundation Fieldbus
5 Connecting to power supply
32765
-EN
-080716