VEGA VEGAPULS 68 (≥ 2.0.0 - ≤ 3.8) 4 … 20 mA_HART four-wire - Manual (Page 26)

5 Connecting to power supply
5.1 Preparing the connection
A lways keep in mind the following safety instructions:
l C onnect only in the complete absence of line voltage
l I f overvoltage surges are expected, overvoltage arresters should
be installed
Tip:
W
e recommend using VEGA overvoltage arresters B63-48 and
ÜSB 62-36G.X.
I n hazardous areas you should take note of the appropriate
regulations, conformity and type approval certificates of the sensors
and power supply units.
S upply voltage and current output are carried on separate two-wire
connection cables if reliable separation is required. The supply voltage
range can differ depending on the instrument version.
T he data for power supply are specified in chapter "Technical data".
T he standard version can be operated with an earth-connected current
output, the Exd version must be operated with a floating output.
T his instrument is designed in protection class I. To maintain this
protection class, it is absolutely necessary that the ground conductor
be connected to the internal ground terminal. Take note of the general
installation regulations.
A s a rule, connect the instrument to vessel ground (potential
euqalisation) or in case of plastic vessels to the next ground potential.
F
or this purpose there is a ground terminal on the side of the
instrument housing.
F or power supply, an approved installation cable with PE conductor is
necessary.
T he 4 … 20 mA current output is connected with standard two-wire
cable without screen. If electromagnetic interference is expected
which is above the test values of EN 61326 for industrial areas,
screened cable should be used.
U se 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.
Note safety instructions
Take note of
safety instruc-
tions for Ex ap-
plications
Select power supply
Selecting connection
cable
26 VEGAPULS 68 • 4 … 20 mA/HART four-wire
5 C onnecting to power supply
29262
-EN
-090305