BEKA BA364E, Руководство пользователя

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7. Pulse output
The BA364G Counter has an opto-isolated solid
state pulse output. The output is an open collector
having the following electrical parameters:
Ron = 60

+ 3V
Roff = 1M
Imax = 10mA
The output pulse may be a duplicate of Input A or
Input b for re-transmission applications, or it may be
derived from the total display.
When derived from
the total display the output pulse frequency may be
divided and the output pulse width defined.
The retransmitted RTx annunciator on the instrument
display shows the status of the retransmitted pulse
output.
Annunciator activation depends upon the
setting of
5ource
in the pulse output configuration
menu.
5caled:
Annunciator activated each time pulse output
open collector is
on , i.e. Ron is less than 60 Ω
+ 3V.
direct:
Annunciator continuously activated
7.1 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
pulse output terminals P1 and P2 to be directly
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 = 200mA
Po = 0.84W
Fig 12 Generating voltage pulse in safe area
using Zener barriers.
The equivalent capacitance and inductance of the
pulse output are both zero which allows the
maximum permissible cable parameters specified by
the certificate for the Zener barrier or galvanic
isolator powering the pulse output circuit to be used.
7.2 System design
The BA364G Counter pulse output is a passive
circuit i.e. not powered, but it is totally isolated from
all other Counter circuits. Subject to complying with
intrinsic safety interconnection requirements, the
terminals P1 and P2 may be connected to another
instrument with an open collector input.
The pulse
output may also be transferred to the safe area via a
galvanic isolator or a Zener barrier.
Fig 12 shows how a 2-channel Zener barrier may be
used to produce a voltage pulse in the safe area that
could be used to drive a safe area counter.
The
positive terminal of the pulse output circuit P1 is
connected to the BA364G Counter’s positive supply
terminal 1 at the instrument. When an output pulse
occurs and the open collector output 'closes', P2 is
connected to P1 and a pulse current flows through
the diode return barrier to resistor R1 in the safe
area. The current flowing in the circuit is determined
by R1 which should be chosen to limit the pulse
output current to less than 10mA. For a 24V supply
R1 should be greater than 2,200
Ω .
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