VEGA VEGAFLEX 62 4 … 20 mA_HART two-wire - Manual (Page 20)

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.
T he data 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, VEGASTAB 690 as well as all
VEGAMET
s and VEGASCANs meet this requirement.
K eep in mind the following additional influences on the operating
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")
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 a different diameter or cross-section, exchange the
seal or use a suitable cable gland.
W e generally recommend the use of screened cable for HART
multidrop mode.
O n the instrument with cable entry ½ NPT and plastic housing there is
a metallic ½" threaded insert moulded into the plastic housing.
Safety instructions
Voltage supply
Connection cable
Cable gland ½ NPT
20 VEGAFLEX 62 • 4 … 20 mA/HART two-wire
5 C onnecting to power supply
31837
-EN
-100426