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

Capacitive electrodes EK - 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 supply
must at least have an intrinsically safe PA
connection. VEGA sensors for PA-Ex
environment are always "ia two-wire
instruments".
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
requirements. The more time-consuming Ex
calculation 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
components (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
instrument is used in hazardous areas, the
required 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
certificates for systems in STEx areas must
be observed.
Electrical connection