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5 Connecting to power supply
Safety instructions
Safety instructions
for Ex applications
Voltage supply
Connection cable
Cable screening and
grounding
Connection cable
for Ex applications
HART communication
10
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.
•
Connect only in the complete absence of line voltage
•
If overvoltage surges are expected, overvoltage arresters should
be installed
In hazardous areas you must take note of the respective regulations,
conformity and type approval certificates of the sensors and power
supply units.
Voltage supply via the 4 ... 20 mA signal cable (loop-powered). A
separate auxiliary voltage is hence not necessary. The current input
of the processing, e.g. a PLC or a display instrument must be active,
i.e. providing the voltage supply of the sensors and the VEGATRENN
151. You can find details of the voltage supply in chapter " Technical
data".
The voltage supply of VEGATRENN 151 is connected with standard
cable according to the national installation standards.
Make sure that the cable used has the required temperature resist-
ance and fire safety for max. occurring ambient temperature
The sensors are connected with standard two-wire cable without
shielding. If electromagnetic interference is expected which is above
the test values of EN 61326 for industrial areas, shielded cable should
be used.
Connect the cable shielding on both ends to ground potential. In
the sensor, the shielding must be connected directly to the internal
ground terminal. The ground terminal on the outside of the sensor
housing must be connected to the potential equalisation (low imped-
ance).
If potential equalisation currents are expected, the connection on the
processing side must be made via a ceramic capacitor (e. g. 1 nF,
1500 V). The low-frequency potential equalisation currents are thus
suppressed, but the protective effect against high frequency interfer-
ence signals remains.
Take note of the corresponding installation regulations for Ex applica-
tions. In particular, make sure that no potential equalisation currents
flow over the cable screen. In case of grounding on both sides this
can be achieved by the use of a capacitor or a separate potential
equalisation described above.
The instrument is equipped with communication sockets in the front
for connection of a VEGACONNECT or another HART handheld as
well as an integrated HART resistor.
VEGATRENN 151 •
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