6
are zero, therefore only switches or intrinsically
safe relays may be connected.
The total maximum permitted cable parameters
for all the cables connected to terminals S1 to S7
in a IIC hydrogen gas must be less than:
Co
=
0.22µF
Lo
=
0.26mH
Although these parameters are not restrictive, for
reliable operation it is recommended that the
cables between the fieldbus display and the
external push buttons are less than 5m long.
3.5 Alarm outputs
Each of the six alarm outputs is a separate
galvanically isolated solid state switch. The EC-
Type Examination Certificate specifies that under
fault conditions the voltage, current and power at
each switch output will not exceed those specified
for
simple apparatus
in Clause 5.4 of
EN50020:2002. This allows each of the BA488CF
alarm outputs to be connected to any intrinsically
safe circuit protected by a certified Zener barrier
or galvanic isolator providing that the output
parameters of each circuit are less than:
Uo =
28V dc
Io
=
200mA
Po =
0.84W
The maximum equivalent capacitance and
inductance of each BA488CF alarm output is:
Ci
= 40nF
Li
= 20µH
To determine the maximum permissible cable
parameters, Ci and Li must be subtracted from the
maximum cable capacitance and inductance
specified by the system certificate of the circuit
connected to the switch.
3.6 Certification Label Information
The certification label is fitted in a recess on the
top outer surface of the enclosure. It shows the
ATEX certification information, a statement that
the instrument is a FISCO Field Device, plus
BEKA associates name and location. Non
European certification information may also be
included.
4. SYSTEM DESIGN FOR HAZARDOUS
AREAS
4.1 FISCO Systems
The BA488CF may be connected to any FISCO
compliant fieldbus segment providing that the
power supply or isolator powering the segment
can provide 25mA required by the BA488CF
Display.
Fig 2 shows a typical fieldbus segment. To
comply with FISCO requirements, the power
supply, terminators, field devices and the
interconnecting cables must conform with
IEC60079 part 27.
Fig 2 FISCO fieldbus system
4.2 Non FISCO Systems
If the BA488CF Fieldbus Display is to be
connected to a fieldbus segment that does not
comply with FISCO requirements, the safety
parameters of the power supply and the Fieldbus
Display must be compared using the entity
concept.
