KROHNE OPTISOUND 3020C 2wire EN - Manual (Page 17)

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 signal are transmitted via the same
two-wire connection cable. The power supply range can differ
depending on the instrument version. The exact range is
stated in the "Technical data" in the Supplement.
Provide a reliable separation between the supply circuit and
the mains circuits acc. to DIN VDE 0106 part 101.
Bear in mind the following factors regarding supply voltage:
l the reduction of the output voltage of the power supply unit
under nominal load (with a sensor current of 20.5 mA or
22 mA in case of fault signal)
l
the influence of additional instruments in the circuit (see
load values in Technical data).
OPTISOUND 3020 C 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 electromagnetic
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).
If potential equalisation currents are expected, the connection
on the evaluation 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 interference signals remains.
Note safety instructions
Take note of safety
instructions for Ex
applications
Select power supply
Selecting the connection ca-
ble
Cable screening and ground-
ing
OPTISOUND 3020 C - 4 … 20 mA/HART 17
Connecting to power supply
30507
-EN
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