BEKA BA384E, Руководство пользователя

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8.2 System design
The Rate Totalisers pulse output is a passive circuit
i.e. unpowered open collector, but it is totally isolated
from all other Rate Totaliser circuits. Subject to
complying with intrinsic safety interconnection
requirements defined in section 8.1, the terminals P1
and P2 may be connected to another instrument that
can accept an open collector input. The pulse
output may also be transferred to the safe area via a
galvanic isolator or a Zener barrier.
Fig 13 shows how a 2-channel Zener barrier may be
used to produce a voltage pulse in the safe area that
could be connected to counter. The positive terminal
of the pulse output circuit P1 is connected to the
Rate totaliser’s positive supply terminal 1 at the Rate
Totaliser. When an output pulse occurs and the
open collector '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 defined by resistor R1 which should
be chosen to limit the pulse current to less than
10mA. For a 24V supply R1 should be greater than
2,200
Ω
Fig 13 Transferring pulse output to safe area using
a Zener barrier.
8.3 Configuration
The pulse output sub-menu is accessed via the
PuL5E oP
function in the configuration menu. The
pulse output sub-menu allows the source of the
output pulse to be selected in the
5ourCE
sub-
function. For re-transmission applications the output
pulse may be a duplicate of one of the input pulses
by selecting
dirECt-A
or
dirECt-b
in the
5ourCE
sub-function. Alternatively, selecting
5CALEd
derives
the output pulse from incrementation of the least
significant digit of the composite total display
input A+ input b.
Note: The
5CALEd
function is not available when
the composite total is
input A
–
input b
.
When
5CALEd
is selected two additional functions,
diVidE
and
durAtion
are added to the sub-menu
allowing the output pulse frequency to be divided
and the output pulse width (duration) to be defined –
see Fig 14.
8.4 Access Pulse output sub-menu:
PuL5E . oP .
Access the Rate Totaliser configuration menu as
described in section 6.2. Using the
&
or
*
push
buttons scroll though the menu until
PuL5E . oP
is
displayed, pressing
(
will then access the pulse
output sub-menu which is shown in Fig 14.
Fig 14 Pulse output configuration sub-menu