VEGA VEGAPULS 65 (≥ 2.0.0 - ≥ 4.0.0) 4 … 20 mA_HART - four-wire - Manual (Page 19)

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5 Connecting to power supply
VEGAPULS 65 • 4 … 20 mA/HART - four-wire
36516-EN-121011
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
In this case, the instrument is designed in protection class II. To main-
tain 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.
Supply voltage and current output are carried on separate connection
cables if reliable separation is required. The supply voltage range can
differ depending on the instrument version.
The data for power supply are specified in chapter "Technical data".
An approved, three-wire installation cable with PE conductor is
required for voltage supply with mains voltage.
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 61326-1 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.
With plastic housing, the NPT cable gland or the Conduit steel tube
must be screwed without grease into the threaded insert.
Max. torque for all housings see chapter "Technical data"
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
suppressed, but the protective effect against high frequency interfer-
ence signals remains.
Warning:
Significant potential differences exist inside galvanization plants as
well as on vessels with cathodic corrosion protection. Considerable
equalisation currents can flow over the cable screen if the screen is
grounded on both ends.
To avoid this in such applications, the cable screen must be connect-
ed to ground potential only at one end (in the switching cabinet). The
Safety instructions
Voltage supply via mains
voltage
Select connection cable
Cable gland ½ NPT
Cable screening and
grounding