BEKA BA364E, Руководство пользователя

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Fig 5 Pulse source in safe area
4.2.1 Power supply
The BA364G Counter requires a minimum of 10V
between terminal 1 & 2 and consumes 10mA plus
6mA for each input that is energised, a maximum
total of 22mA if both inputs are energised.
The
optional backlight increases the current consumption
by 16mA. Any certified galvanic isolator may be
used to power a BA364G Counter providing the
output safety parameters of the isolator are equal to
or less than the input safety parameters of terminals
1 & 2 of the BA364G Counter. These requirements
are not restrictive and allow a wide range of galvanic
isolators, such as solenoid drivers, to be used.
4.2.2 Pulse input
As shown in Fig 4 the BA364G can count pulses
from a wide variety of sensors in the hazardous
area, or from the safe area as shown in Fig 5.
No galvanic isolator is required in series with the
input if the intrinsically safe pulse source is located
within the same hazardous area as the BA364G
Counter.
The following table shows the switching thresholds
for the various types of sensor.
For reliable
counting the pulse input must fall below the lower
threshold and rise above the upper threshold.
Input sensor
Switching thresholds
Lower Upper
Switch
100

1000

Proximity detector 1.2mA 2.1mA
Open collector
2k

10k

Magnetic pick-off 0mV 40mV peak
Voltage pulse low 1.0V 3.0V
Voltage pulse high 3.0V 10.0V
4.2.3 Switch contact input
Any mechanically activated switch contact located in
the same hazardous area as the BA364G Counter
may be directly connected to pulse input terminals 5
& 6 or 9 & 10 providing the switch and associated
wiring can withstand a 500V rms insulation test to
earth.
Most magnetically activated reed relays
comply with these requirements. The BA364G
contains a configurable debounce circuit to prevent
contact bounce being counted. Three levels of de-
bounce protection are independently available. See
section 6.6.
See section 6.6 for details of the typical maximum
counting frequency.
4.2.4 2-wire proximity detector input
Most certified intrinsically safe 2-wire proximity
detectors
complying with NAMUR switching
thresholds may be connected to the BA364G
Counter inputs, providing the input safety parameters
of the proximity detector are equal to or greater than
the output safety parameters of the Counter inputs
i.e.
Ui ≥ 10.5V dc
Ii ≥ 9.2mA dc
Pi
≥
24mW
and the minimum operating voltage of the proximity
detector is less than 7.5V.
See section 6.6 for details of the typical maximum
counting frequency.
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