VEGA VEGAFLEX 66 (-110…+400°C) 4 … 20 mA_HART - Manual (Page 18)

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.
P
ower supply and current signal are carried on the same two-
wire cable. The voltage supply range can differ depending on
the instrument version.
D ata for power supply are specified in chapter "Technical
data".
P
rovide a reliable separation between the supply circuit and
the mains circuits according to DIN VDE 0106 part 101. The
VEGA
power supply units VEGATRENN 149A Ex, VEGAS-
TAB 690 as well as all VEGAMETs meet this requirement.
B ear in mind the following factors regarding supply voltage:
l
O
utput voltage of the power supply unit can be lower under
nominal load (with a sensor current of 20.5 mA or 22 mA in
case of fault message)
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I nfluence of additional instruments in the circuit (see load
values in chapter "Technical data")
T he instrument 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 other diameter or cross-
section, you have to 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
18 VEGAFLEX 66 • 4 … 20 mA/HART
5 C onnecting to power supply
32762
-EN
-080716