KROHNE SU 501 EX EN - Manual (Page 12)

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.
The power supply can be 20 … 250 V AC, 50/60 Hz or
20 … 72 V DC.
Power supply of SU 501 Ex is connected with standard cable
acc. to the national installation standards.
Standard two-wire cable without screening can be used to
connect sensors. If electromagnetic interference is expected,
screened cable must be used.
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
sensor housing must be connected to the potential equalisa-
tion.
If potential equalisation currents are expected, the screen
connection on SU 501 Ex 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.
Take note of the corresponding installation regulations for Ex
applications. 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.
5.2 Connection procedure
Move to electrical connection and proceed as follows:
1 Snap the socket without SU 501 Ex onto the carrier rail
Note safety instructions
Take note of safety
instructions for Ex
applications
Select power supply
Select connection cable
Cable screening and groun-
ding
Select connection
cable for Ex applica-
tions
12 SU 501 Ex - Signal conditioning instrument
Connecting to power supply
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-EN
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