BEKA BA334E, Руководство пользователя, Страница: 28 / 64

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6.23 Reset configuration to factory defaults
r5et def
This function resets the Rate Totaliser including the
lineariser, to the factory default configurations which
are shown in section 6.0
To reset the Rate Totaliser to the factory default
configurations select
r5Et def
from the configuration
menu and press
(
which will result in a
0000
display with the first digit flashing. This is a request
to confirm the reset to factory default instruction by
entering
5urE
. Using the
&
or
*
button set the
flashing digit to
5
and press
(
to transfer control to
the second digit which should be set to
u
. When
5urE
has been entered, pressing the
)
button will
reset the BA334G to the factory defaults and return
the instrument to the totalising mode.
6.24 Pulse output
All BA334G Rate Totalisers have an opto-isolated
pulse output.
The pulse output is an open collector having the
following parameters:
Ron = 60 Ω + 3V
Roff = 1M
I max = 10mA
The output pulse may be a duplicate of the input
pulse for re-transmission applications, or it may be
derived from the least significant digit of the total
display. When derived from the total display the
output pulse frequency may be divided and the
output pulse width defined.
6.24.1 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 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 dc
Po ≤ 0.84W
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.
6.24.2 System design
The Rate Totalisers pulse output is a passive
circuit i.e. not powered, but it is totally isolated from
all other Rate Totaliser 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 11 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 Rate totaliser’s
positive supply terminal 1. When an output pulse
occurs and the open collector output ‘closes’, P2
is connected to P1 and the 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