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5 Connecting to power supply
OPTISOUND 3020 C • Two-wire 4 … 20 mA/HART
30507-EN-190318
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,
qualified 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.
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.
On the instrument with cable entry ½ NPT and plastic housing there is
a metallic ½" threaded insert moulded into the plastic housing.
Caution:
No grease should be used when screwing the NPT cable gland or
steel tube into the threaded insert. Standard grease can contain
additives that corrode the connection between threaded insert and
housing. This would influence the stability of the connection and the
tightness of the housing.
Safety instructions
Voltage supply
Connection cable
Cable gland ½ NPT