BEKA BA538C, Manual

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5
3.3 Pulse input
As shown in Fig 2, the BA538C will count pulses
from a wide variety of transducers enabling it to
display the output from almost any flowmeter.
The instrument has one pulse input, but two sets
of input terminals enable it to accommodate
different types of transducers. Terminals 3 and 4
are for voltage pulse inputs and terminals 5 and 6
are for pulse sources that need powering i.e.
proximity detectors, switches and open collectors.
Note: Only one pair of input terminals may be
used at a time. i.e pulses can not be counted
from terminals 3 & 4 and from terminals 5 & 6 at
the same time.
The following table shows the switching
thresholds for the various transducers, plus the
maximum operating frequency and the input
terminal numbers. For reliable counting the input
signal must fall below the lower threshold and rise
above the upper threshold.
Switching
thresholds
Freq
max
Input
terminals
Switch 100

1000

100Hz 5 & 6
Proximity
detector
1.2mA 2.1mA 5 kHz 5 & 6
Open
collector
2k

10k

5kHz 5 & 6
Magnetic
pick-off
0mV 20mV
peak
5kHz 3 & 4
Voltage
pulse
1.0V 3.0V 5kHz 3 & 4
3.4 Remote reset
The BA538C total display is reset to zero when
terminals 7 & 8 are connected together for more
than one second. Permanent interconnection of
these terminals will stop totalisation and may be
used as an inhibit function. There is no practical
limit on the distance that the reset switch may be
from the totaliser.
Alternatively, the BA538C may be programmed so
that the total display is reset to zero when the
Up
and Down push-buttons are operated
simultaneously for more than two seconds. – see
5.12
4. INSTALLATION
4.1 Location
The BA538C is housed in a robust aluminium
enclosure with a polyester membrane front panel
surrounded by a Noryl bezel. The front of the
instrument provides IP65 protection and a gasket
seals the joint between the instrument enclosure
and the panel. The instrument may be installed in
any panel providing the environmental limits
shown in the specification are not exceeded.
Although the front panel of the instrument has
IP65 protection, the BA538C is not intended for
external mounting. Please refer to BEKA
associates if external mounting is required.
Fig 3 shows the overall dimensions of the BA538C
and the panel cut-out. To achieve an IP65 seal
between the instrument enclosure and the panel
the smaller cut-out must be used and the
instrument secured with four panel mounting clips.
The BA538C liquid crystal display has maximum
contrast when viewed from directly ahead and
slightly below the centre line of the instrument.
For reflective displays there is little degradation of
contrast when viewed from above the centre line,
but slight degradation may be noticeable when the
instrument is fitted with a backlight.
Fig 3 BA538C dimensions