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2.4.1 Power supply
The BA364D galvanic isolator system certificate
lists a wide range of certified galvanic isolators
that may be used to power the instrument. If
using the entity concept to select an isolator, in
addition to matching the safety parameters, the
isolator must be capable of supplying 10V dc
minimum at 20mA to the BA364D.
2.4.2 Input
When the BA364D is programmed as a counter
both input A and input B are operational. These
inputs may be independently programmed to
operate with almost any pulse output transducer.
The following table shows the switching
thresholds for the various transducers, plus the
maximum operating frequency. For reliable
counting the input signal must fall below the
lower threshold and rise above the upper
threshold.
Input
Switching
thresholds
Freq.
max
Switch
100
1000
100Hz
Proximity
detector
1.2mA
2.1mA
5kHz
Open
collector
2k
10k
5kHz
Magnetic
pick-off
0mV
20mV
peak
5kHz
Voltage
pulse
1.0V
3.0V
5kHz
The intrinsic safety requirements are explained in
section 1.4.3 Almost any mechanically or
magnetically activated switch, or intrinsically safe
NAMUR 2-wire proximity detector may be directly
connected to the input terminals.
If the BA364D is located in a hazardous area but
the transducers are in the safe area, a galvanic
isolator is required to transfer the transducer
output(s) to the instrument. The system
certificate defines some of the devices which may
be used.
2.4.3 Resetting the total display
When terminals 7 & 8 are connected together the
total display will be reset. To achieve reliable
resetting the contacts must close for at least one
second.
Resetting may be accomplished by any
mechanically operated switch located in the
hazardous area providing it can withstand a 500V
rms insulation test to earth for one minute. No
galvanic isolator is required.
The BA364D may also be reset from within the
safe area. Any switch may be used, but a
galvanic isolator or intrinsically safe relay is
required to transfer the contact closure into the
hazardous area. See system certificate for a list
of some devices that may be used. Fig 2.2
illustrates how the BA364D may be reset from
both the safe and the hazardous area.
2.4.4 Options
When the BA364D is calibrated as a counter,
optional alarms, a 4/20mA analogue output and a
re-transmitted pulse output may be used. The
intrinsic safety features of these options are
described in section 1 of this manual and the
counter applications in sections 2.6, 2.7 and 2.8.
