BEKA BA334E, Руководство пользователя, Страница: 14 / 64

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4.2.5 2-wire proximity detector input
Most certified intrinsically safe flowmeters
incorporating a NAMUR 2-wire proximity detector
may be directly connected to a BA334G input,
providing the input safety parameters of the
proximity detector are equal to or greater than the
output safety parameters of a BA334G input. The
(flowmeter) proximity detector input safety
parameters should be:
Ui ≥ 10.5V dc
Ii ≥ 8.2mA dc
Pi ≥ 24mW
and the minimum operating voltage of the flowmeter
(proximity detector) is less than 7.5V. The flowmeter
must be located in the same hazardous area as the
Rate Totaliser, and with the associated wiring, be
able to withstand a 500V rms insulation test to earth.
The BA334G contain a configurable debounce
circuit to prevent false triggering of the instrument.
Three levels of de-bounce protection are available.
See section 6.7.
4.2.6 Magnetic pick-off input
Flowmeters incorporating a magnetic pick-off to
sense flow will have a low level voltage output
unless the flowmeter incorporates an amplifier.
CoiL
in the BA334G input configuration menu is a low
level voltage pulse input intended for use with an
intrinsically safe magnetic pick-off. When a Rate
Totaliser input is configured for
CoiL
and terminals 3
& 4 are not linked, input terminals 5 & 6 comply with
the requirements for
simple apparatus allowing
connection to any certified intrinsically safe
magnetic sensor having output parameters equal to
or less than:
Uo ≤ 28V dc
Io ≤ 200mA dc
Po ≤ 0.84W
The maximum permitted cable parameters will be be
the flowmeter's Co and Lo specified on it's intrinsic
safety certificate, less the Rate Totalisers pulse input
parameters Ci and Li which are small and can often
be ignored.
The flowmeter must be located within the same
hazardous area as the BA334G and with the
associated wiring must be able to withstand a 500V
rms insulation test to earth.
The BA334G contain a configurable debounce
circuit to prevent false triggering of the instrument.
Three levels of de-bounce protection are
independently available. See section 6.7.
4.2.7 Voltage pulse input
Two voltage pulse input ranges are independently
selectable in the BA334G Rate Totalisers
configuration menu,
VoLt5 L
and
VoLt5 H
. When
configured for either of the voltage pulse ranges,
and terminals 3 & 4 are not linked, the input
terminals 5 & 6 comply with the requirements for
simple apparatus . This allows the pulse input to be
connected to any certified intrinsically safe
flowmeter with a voltage output located within the
same hazardous area as the Rate Totaliser
providing it has output parameters equal to or less
than:
Uo ≤ 28V dc
Io ≤ 200mA dc
Po ≤ 0.84W
The BA334G Rate Totalisers may therefore be
directly connected to most certified intrinsically
safe flowmeters with a high level voltage output.
The maximum permitted cable parameters will be
defined by the flowmeter's intrinsic safety Co and
Lo less the Rate Totaliser's pulse input parameters
Ci and Li which are small and can often be
ignored.
The BA334G contains a configurable debounce
circuit to prevent false triggering of the instrument.
Three levels of de-bounce protection are
available. See section 6.7.
4.2.8 Remote reset
The Rate Totaliser's total display may be remotely
reset to zero by connecting terminals 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 galvanic
isolator is required.
A BA334G may also be remotely reset from the
safe area. Any switch may be used but a galvanic
isolator is required to transfer the contact closure
into the hazardous area. Fig 4 illustrates how a
BA334G may be reset from both the safe and the
hazardous area.
Note: The BA334G Rate Totaliser may be
configured to reset the total display to zero
by operating the
&
and
*
push buttons
simultaneously for more than three
seconds in the totalising mode i.e. when
the instrument is displaying flow. See
6.19