BEKA BA334NG, Manual

Page: 25 / 46

25
6.24.2 System design
The Rate Totaliser’s 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 Ex nA interconnection requirements, the
terminals P1 and P2 may be connected to any other
instrument with an open collector pulse input.
Fig 11 shows how 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
the pulse output current to less than 10mA. For a
24V supply R1 should be greater than 2,200
Ω .
Fig 11 Transferring pulse output to the safe area
using Zener barriers
6.24.3 Configuration
The pulse output menu shown in Fig 12 is in the
BA334NG configuration menu. The output pulse
may be a duplicate of the input pulse by selecting
dirECt
in the
5ourCE
sub-function. Alternatively,
selecting
5CALEd
derives the output pulse from
incrementation of the least significant digit of the
total display. 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.
6.24.4 Pulse output:
PuL5E oP
The pulse output is configured in a sub-menu
contained in the
pul5e op
function.
Using the
&
or
*
push button scroll though the
configuration menu until
PuL5E oP
is displayed,
pressing
(
will then access the pulse output sub-
menu which is shown in Fig 12.
Fig 12 Pulse output configuration sub-menu