30
The pulse output will sink up to 10mA. When
closed the voltage between the pulse output
terminals P1 & P2 will be less than 3V when
switching 5mA.
Fig 17 Pulse output menu
9.5.1 Intrinsic safety
The pulse output is an optically isolated separate
intrinsically safe circuit that has zero output safety
parameters. The output 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 dc
Io
=
100mA
Po =
0.7W
The maximum equivalent capacitance and
inductance of the BA338C pulse output is:
Ci
= 20nF
Li
= 20µH
To determine the maximum permissible cable
parameters, these figures should be subtracted
from the maximum cable capacitance and
inductance specified by the system certificate of
the circuit connected to the BA338C. Fig 16
shows how the pulse output circuit may be
powered from the BA338C supply to drive a
counter in the safe area via a diode return barrier.
9.6 4/20mA output
The optional 4/20mA output may be programmed
to produce an analogue output proportional to the
whole or part of the rate display. The output is a
current sink which requires between 5 and 28V to
function as shown in Fig 18.
9.6.1 Intrinsic safety
The 4/20mA output has been certified as a
separate intrinsically safe circuit complying 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 dc
Io
=
100mA
Po =
0.7W
No system certificate has been issued for this
output as the system certificate for the circuit to
which it is connected remains valid.
Fig 18 Application of 4/20mA output
