KROHNE OPTISOUND 3020C 4wire EN - Manual (Page 18)

5 Connecting to power supply
5.1 Preparing the connection
Always observe the following safety instructions:
l
Connect only in the complete absence of line voltage
l
If overvoltages are expected, overvoltage arresters should
be installed.
In hazardous areas you should take note of the appropriate
regulations, conformity and type approval certificates of the
sensors and power supply units.
Power supply and current output are transmitted via separate
two-wire connection cables. The power supply range can differ
depending on the instrument version. The exact range is
stated in the "Technical data" in the Supplement.
The standard version can be operated with an earth-
connected current 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.
As a rule, connect OPTISOUND 3020 C to vessel ground
(potential equalisation), or in case of plastic vessels, to the
next ground potential. There is a ground terminal on the side of
the instrument housing.
For power supply, an approved installation cable with PE
conductor is necessary.
The 4 ... 20 mA current output is connected with standard two-
wire cable without screen. An outer cable diameter of 5 ...
9 mm ensures the seal effect of the cable entry. If electro-
magnetic interference is expected, we recommend the use of
screened cable.
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 outside on the
housing must be connected to the potential equalisation (low
impedance).
Note safety instructions
Take note of safety
instructions for Ex
applications
Select power supply
Selecting the connection ca-
ble
Cable screening and ground-
ing
18 OPTISOUND 3020 C - 4 ... 20 mA/HART - four-wire
Connecting to power supply
30508
-EN
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