VEGA VEGAFLEX 67 (-20…+250°C) 4 … 20 mA_HART four-wire - Manual (Page 15)

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 must take note of the respective 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
lways connect the instrument to vessel ground (potential equal-
isation) or in case of plastic vessels to the next ground potential. For
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
required.
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.
I f screened cable is necessary, connect the cable screen on both ends
to ground potential. In the sensor, the screen must be connected
directly to the internal ground terminal. The ground terminal on the
outside of the housing must be connected to the potential equalisation
(
low impedance).
Note safety instructions
Take note of the
safety instru-
ctions for Ex
applications
Voltage supply
Connection cable
Cable screening and
grounding
VEGAFLEX 67 • 4 … 20 mA/HART - four-wire 15
5 C onnecting to power supply
32308
-
EN
-120329