9
1.9.5.2 Intrinsic safety
Both control outputs comply with the
requirements for
simple apparatus
specified in
Clause 5.5 of EN50020:1994. This allows them
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 do not exceed:
Uo =
28Vc
Io
=
200mA dc
Po =
0.85W
No system certificate has been issued for the
BA364D switch contact outputs, as the system
certificate for the circuit to which the alarms are
connected remains valid.
The maximum equivalent capacitance and
inductance of each BA364D control output is:
Ci
= 40nF
Li
= 30µH
To determine the maximum permissible cable
parameters, the equivalent output parameters
must be subtracted from the maximum cable
capacitance and inductance specified by the
system certificate of the circuit connected to each
control output.
1.9.6 Optional pulse output
The BA364D can be supplied with an isolated
solid state pulse output for use when the
instrument is programmed as a counter. Section
2 of the manual explains the use and
programming of this option
1.9.6.1 Intrinsic safety
The pulse output is an optically isolated separate
intrinsically safe circuit that has zero output
safety parameters and therefore complies with
the requirements for
simple apparatus.
This
allows terminals P1 and P2 to be connected to
any intrinsically safe circuit protected by a
certified Zener barrier or galvanic isolator
providing the output parameters do not exceed:
Uo =
28V
Io
=
100mA dc
Po =
0.7W
The maximum equivalent capacitance and
inductance of the BA364D pulse output is:
Ci
= 20nF
Li
= 20µH
To determine the maximum permissible cable
parameters, these figures must be subtracted
from the maximum permitted cable capacitance
and inductance specified by the system
certificate of the circuit connected to the BA364D
– usually a Zener barrier or galvanic isolator.
1.9.7 Optional 4/20mA output
The BA364D can be supplied with an optically
isolated 4/20mA current sink which may be used
when the instrument is programmed as a counter
or as a tachometer. When the BA364D is
programmed as a counter, the 4/20mA output
may be proportional to pulse input rate or the
total number of pulses. When programmed as a
tachometer the current is proportional to
rotational speed.
Note:
The 4/20mA current output is not available
when the BA364D is programmed as a timer or
as a clock.
1.9.7.1 Intrinsic safety
The 4/20mA output is an optically isolated
separate intrinsically safe circuit which has zero
output safety parameters and therefore complies
with the requirements for
simple apparatus.
This
allows terminals C1 and C2 to be connected to
any intrinsically safe circuit protected by a
certified Zener barrier or galvanic isolator
providing the output parameters do not exceed:
Uo =
28V
Io
=
100mA
Po =
0.7W
The maximum equivalent capacitance and
inductance of the optional 4/20mA output at the
terminals is:
Ci
= 2nF
Li
= 8µH
To determine the maximum permissible cable
parameters, these figures must be subtracted
from the maximum cable capacitance and
inductance specified by the system certificate of
the circuit connected to the BA364D 4/20mA
output – usually a Zener barrier or galvanic
isolator.
