6
Uo
=
14.7V dc
Io
=
146.7mA dc
Po
=
0.58W
The switches and associated wiring connected to
the terminals must comply with the requirements
for
simple apparatus
. i.e. the switch must be
mechanically activated and have IP20 protection,
and both the switch and the wiring must be
capable of withstanding a 500V rms insulation test
to earth for one minute. Most industrial push
buttons and wiring satisfy these requirements.
The input safety parameters of terminals S1 to S7
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 section 5.7 of EN 60079-
11. This allows each of the BA488CF-P 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-P 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-P 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-P
PROFIBUS 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 EN 60079 part 27.
Fig 2 FISCO fieldbus system