BEKA BA368C, Руководство пользователя

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2.4.1 Power supply
The BA368C 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 BA368C.
2.4.2 Input
When the BA368C 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
Ω
1000
Ω
100Hz
Proximity
detector
1.2mA 2.1mA 5kHz
Open
collector
2k
Ω
10k
Ω
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 BA368C 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 BA368C 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 BA368C may be reset from both the safe
and the hazardous area.
2.4.4 Options
When the BA368C 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.