BEKA BA334D, Manual

Page: 10 / 43

10
Switching
thresholds
Freq
max
Input
terminals
Switch
100
Ω
1000
Ω
100Hz 5 & 6
Proximity
detector
1.2mA 2.1mA 5 kHz 5 & 6
Open
collector
2k
Ω
10k
Ω
5kHz 5 & 6
Magnetic
pick-off
0mV 20mV
peak
5kHz 3 & 4
Voltage
pulse
1.0V 3.0V 5kHz 3 & 4
4.3.3 Switch contact input
Any mechanically activated switch contact
located in the hazardous area may be directly
connected to terminals 5 & 6 providing it can
withstand a 500V rms insulation test to earth
for one minute. This includes most
magnetically activated reed relays used in
turbine flowmeters. The BA334D contains
filtering to prevent contact bounce being
counted which limits the maximum operating
frequency for a switch contact to 100Hz.
4.3.4 2-wire proximity detector input
Any certified intrinsically safe 2-wire proximity
detector listed on the system certificate may be
connected to input terminals 5 and 6. The
BA334D input complies with the NAMUR
switching standard and other certified
intrinsically safe detectors may be used
providing the safety parameters of the
proximity detector are compatible with the
BA334D.
When programmed to operate with a proximity
detector, the BA334D maximum input
frequency is 5kHz.
4.3.5 Voltage pulse input
Voltage pulse sources should be connected to
terminals 3 and 4. These terminals comply
with the requirements for simple apparatus.
They may be directly connected to any certified
intrinsically safe voltage source within the
hazardous area, providing it can withstand a
500Vrms insulation test to earth for one minute
and has output parameters equal to or less
than:
Uo = 28V dc
Io = 100mA dc
Po = 0.7W
This enables the BA334D to be connected
directly to most flowmeters incorporating a
certified intrinsically safe magnetic pick-off, or
a certified intrinsically safe amplifier producing
a high level pulse output. The BA334D has
two programme selectable voltage switching
thresholds, ‘COIL’ for magnetic pick-offs and
‘UOLtS’ for higher voltage pulses.
Maximum voltage pulse counting frequency is
5kHz.
4.3.6 Remote reset
The BA334D total display is reset to zero
when terminals 7 & 8 are connected together
for more than one second. Permanent
interconnection inhibits totalisation. Remote
resetting may be accomplished by any
mechanically operated switch located in the
hazardous area providing it can withstand a
500Vrms insulation test to earth for one
minute. No galvanic isolator is required.
The BA334D may be reset to zero from the
safe area. Any switch may be used but a
galvanic isolator is required to transfer the
contact closure into the hazardous area. Fig 4
illustrates how the BA334D may be reset from
both the safe and the hazardous area.
Note: The BA334D can be programmed to
reset the total display to zero when the up and
down push-buttons are operated
simultaneously for more than two seconds. –
see 6.12.