BEKA BA384E, Manual

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The flowmeter must be located within the same
hazardous area as the BA384G and with the
associated wiring be able to withstand a 500V rms
insulation test to earth.
The BA384G contains a configurable debounce
circuit to prevent false triggering of the instrument.
See section 6.7.
4.1.7 Voltage pulse input
Two voltage pulse input ranges are independently
selectable in the BA384G Rate Totaliser
configuration menu,
VoLt5 L
and
VoLt5 H
. When
configured for either of the voltage pulse ranges, the
input terminals 5 & 6 and 9 & 10 comply with the
requirements for
simple apparatus . This allows the
inputs to be connected to any certified intrinsically
safe voltage source within the same hazardous area
as the BA384G having output parameters equal to
or less than:
Uo ≤ 28V dc
Io ≤ 200mA dc
Po ≤ 0.84W
The BA384G Rate Totaliser may therefore be
directly connected to most certified intrinsically safe
flowmeters with a high level voltage pulse output.
The maximum permitted cable parameters will be
defined by the intrinsic safety certification of the
flowmeter less the BA384G input parameters which
are small and can often be ignored.
The BA384G contains a configurable debounce
circuit to prevent false triggering of the instrument.
Three levels of de-bounce protection are
independently available for each input,
See section 6.7.
4.1.8 Remote reset
The BA384G total display may be remotely reset to
zero by connecting RS1 and RS2 together for more
than one second. Permanent interconnection
inhibits totalisation. Remote resetting may be
accomplished by any mechanically operated switch
located in the same hazardous area as the Rate
Totaliser providing the switch and the associated
wiring can withstand a 500V rms insulation test to
earth. No Zener barrier is required.
A BA384G may also be remotely reset from the safe
area. Any switch may be used but a Zener barrier
is required to transfer the contact closure into the
hazardous area which may be combined with the
supply barrier so that only one package is required.
A diode return barrier is not suitable for this
application. Fig 2 illustrates how a BA384G may be
reset from both the safe and the hazardous area.
Note: The BA384G may be configured to reset the
total display to zero by operating the
&
and
*
push buttons simultaneously for more
than two seconds in the totalising mode i.e.
when the instrument is displaying flow.
See 6.20
4.2 Use with Galvanic Isolators
Galvanic isolators are probably the simplest
intrinsically safe interface to install as they provide
isolation and do not require a high integrity earth
connection.
Any galvanic isolator certified for the gas group in
which the BA384G is installed, with output
parameters less than the input parameters of the
BA384G having the correct function may be used.
Fig 4 BA384G used with galvanic isolators
Fig 4 illustrates the basic circuit that is used for all
BA384G installations protected by galvanic isolators.
For simplicity, connections for the optional pulse
output, 4/20mA output and alarms are shown in
sections 8 and 11 of this manual.
Alternatively flowmeters may be located in the safe
area. Fig 5 shows how additional galvanic isolators
are used to transfer the pulse signal to the BA384G
in the hazardous area, although it may be difficult to
find isolators for some flowmeters. The two
BA384G external input conditioning links should be
positioned to match the output of the galvanic
isolator not the flowmeter.