VEGA VEGABAR 74 4 … 20 mA_HART - Manual (Page 13)

5 C onnecting 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, versions with inte-
grated overvoltage arresters should be used or external
overvoltage arresters should be installed
Tip:
W
e recommend the version of VEGABAR 74 with integrated
overvoltage arrester or VEGA type ÜSB62-36G.X as external
overvoltage arreaster.
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.
T he data for power supply are stated in chapter "Technical
data" in the "Supplement".
P rovide a reliable separation of the supply circuit from the
mains circuits according to DIN VDE 0106 part 101.
VEGA
power supply units VEGATRENN 149AEx, VEGASTAB
690, VEGADIS 371 as well as all VEGAMETs meet this
requirement. When using one of these instruments, protection
class III is ensured for VEGABAR 74.
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)
l
I nfluence of additional instruments in the circuit (see load
values in chapter "Technical data")
VEGABAR 74 is connected with standard two-wire cable
without screen. An outer cable diameter of 5 … 9 mm ensures
the seal effect of the cable gland when connecting via
VEGABOX
02 or VEGADIS 12. If electromagnetic interference
is expected which is above the test values of EN 61326 for
Note safety instructions
Take note of safety
instructions for Ex
applications
Select power supply
Selecting connection cable
VEGABAR 74 - 4 … 20 mA/HART 13
C onnecting to power supply
28432
-
EN
-070718