VEGA VEGASON 61 4 … 20 mA_HART - four-wire - Manual (Page 17)

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5 Connecting to power supply
VEGASON 61 • 4 … 20 mA/HART - four-wire
28778-EN-130417
5 Connecting to power supply
5.1 Preparing the connection
Always keep in mind the following safety instructions:
•
Connect only in the complete absence of line voltage
•
If overvoltage surges are expected, overvoltage arresters should
be installed
Tip:
We recommend using VEGA overvoltage arresters B63-48 and
ÜSB 62-36G.X.
In hazardous areas you must take note of the respective regulations,
conformity and type approval certificates of the sensors and power
supply units.
Supply voltage and current output are carried on separate two-wire
connection cables if reliable separation is required. The supply volt-
age range can differ depending on the instrument version.
The data for power supply are specified in chapter "Technical data".
The standard version can be operated with an earth-connected cur-
rent output, the Exd version must be operated with a floating output.
This instrument is designed in protection class I. To maintain this
protection class, it is absolutely necessary that the ground conductor
be connected to the internal ground terminal. Take note of the general
installation regulations.
Always connect the instrument to vessel ground (potential equalisa-
tion) or in case of plastic vessels to the next ground potential. For
this purpose there is a ground terminal on the side of the instrument
housing.
For power supply, an approved installation cable with PE conductor is
required.
The 4 … 20 mA current output 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.
Use 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.
If screened cable is necessary, connect the cable screen on both
ends to ground potential. In the sensor, the screen must be connected
directly to the internal ground terminal. The ground terminal on the
outside of the housing must be connected to the potential equalisa-
tion (low impedance).
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
Note safety instructions
Take note of safety
instructions for Ex
applications
Voltage supply
Connection cable
Cable screening and
grounding