BEKA BA364D, Руководство пользователя

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3.4.1 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.
3.4.2 Inputs
When the BA364D is programmed as a timer
both input A and input B are operational and may
be independently programmed to operate with
almost any pulse output transducer.
The following table shows the switching
thresholds for the various transducers. For
reliable operation the input signal must fall below
the lower threshold and rise above the upper
threshold.
Input Switching
thresholds
Switch
100 1000
Proximity
detector
1.2mA 2.1mA
Open
collector
2k 10k
Magnetic
pick-off
0mV 20mV
peak
Voltage
pulse
1.0V 3.0V
The intrinsic safety requirements are explained in
section 1.4.3 Almost any mechanically or
magnetically activated switch, intrinsically safe
NAMUR 2-wire proximity detector or intrinsically
safe voltage may be directly connected to these
two inputs.
If the BA364D is located in a hazardous area but
the transducer(s) is in a safe area, a galvanic
isolator is required to transfer the transducer
output to the instrument. The system certificate
defines some galvanic isolators which may be
used.
3.4.3 Resetting the timer
When terminals 7 & 8 are connected together the
timer will be reset to zero if counting up, and to
the set time (‘SEt t’) if counting down. 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 timer may also be reset from within
the safe area. Any switch may be used but a
galvanic isolator is required to transfer the
contact closure into the hazardous area. The
system certificate lists some of devices that may
be used.
Fig 3.2 illustrates how the timer may be reset
from both the safe and the hazardous areas.
3.4.4 Options
When the BA364D is conditioned as a timer,
optional control outputs may be used. The
intrinsic safety features of these are described in
section 1.9.5.2 of this manual.