VEGA Capacitive electrodes EL Profibus PA - Manual (Page 23)

Capacitive electrodes EL - Profibus PA 23
Profibus PA in Ex environment
For application in Ex areas, the PA bus and
all connected instruments must be certified
as intrinsically safe protective class "i". Four-
wire instruments requiring a separate power
supply must at least have an intrinsically safe
PA connection. VEGA sensors for PA-Ex
environment are always "ia two-wire instru-
ments".
In the so-called Fieldbus Intrinsically Safe
Concept (FISCO), the general conditions for
an Ex safe bus configuration have been laid
down. Therein, the participants and the bus
cables with their respective electrical data
have been determined, so that the linking of
these components always meets Ex require-
ments. The more time-consuming Ex calcula-
tion normally required is therefore not
necessary. Build your Ex bus according to
the IEC standard 1158-2.
The Ex segment coupler delivers a controlled
power supply to the PA bus. All other compo-
nents (field instruments and bus terminators)
are only consumers. A field instrument must
consume at least 10 mA. Ideally, an individual
sensor should not consume more than
10 mA, so that the number of instruments can
be as large as possible.
Watch out for potential losses
Due to potential losses, earthing on both
sides without a potential equalisation system
is prohibited in Ex applications. If an instru-
ment is used in hazardous areas, the re-
quired regulations, conformity and type
approval certificates for systems in Ex areas
must be noted (e.g. DIN 0165). Please also
note the approval documents with the safety
data sheet attached to the Ex sensors.
Ex protection
If an instrument is used in dust Ex areas, the
required regulations as well as the StEx cer-
tificates for systems in StEx areas must be
observed.
Electrical connection