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5 Connecting to power supply
VEGAPULS 66 • 4 … 20 mA/HART - two-wire
28438-EN-170927
5 Connecting to power supply
5.1 Preparing the connection
Always keep in mind the following safety instructions:
Warning:
Connect only in the complete absence of line voltage.
•
The electrical connection must only be carried out by trained
personnel authorised by the plant operator.
•
If overvoltage surges are expected, overvoltage arresters should
be installed.
Power supply and current signal are carried on the same two-wire
cable. The operating voltage can differ depending on the instrument
version.
The data for power supply are specified in chapter "
Technical data
".
Provide a reliable separation between the supply circuit and the
mains circuits according to DIN EN 61140 VDE 0140-1.
Power the instrument via an energy-limited circuit acc. to DIN/EN/IEC/
ANSI/ISA/UL/CSA 61010-1, e.g. via Class 2 power supply unit acc. to
UL 1310 or an SELV power supply unit with suitable external current
limitation.
1)
Keep in mind the following additional factors that influence the operat-
ing voltage:
•
Lower output voltage of the power supply unit under nominal load
(e.g. with a sensor current of 20.5 mA or 22 mA in case of fault)
•
Influence of additional instruments in the circuit (see load values in
chapter "
Technical data
")
The instrument is connected with standard two-wire cable without
screen. If electromagnetic interference is expected which is above the
test values of EN 61326-1 for industrial areas, screened cable should
be used.
Make sure that the cable used has the required temperature resist-
ance and fire safety for max. occurring ambient temperature
Use cable with round cross section for instruments with housing and
cable gland. To ensure the seal effect of the cable gland (IP protection
rating), find out which cable outer diameter the cable gland is suitable
for.
Use a cable gland fitting the cable diameter.
We generally recommend the use of screened cable for HART
multidrop mode.
Safety instructions
Voltage supply
Connection cable
1)
Class 2 power supply unit: limited voltage and power level, special insulation
against circuits with higher voltage. SELV (Safety Extra Low Voltage) power
supply unit: limited voltage level, special insulation against circuits with
higher voltage
