BEKA BA364G, Manual, Page: 8 / 40

4.1 Power supply
The BA367NE Counter requires a minimum of 10V
between terminal 1 & 2 and consumes:
10mA without optional backlight
plus 6mA when terminals 3 & 4 are linked
A 24V dc regulated supply with a current limit
located in a safe area is suitable. The power supply
should meet the requirements for personnel safety
so that ‘live maintenance’ can safely be performed.
The implicit requirement for galvanic isolation from
the mains supply ensures that the possible
difficulties from circulating earth currents caused by
mains faults is minimised. In European terms if the
power supply is CE marked it is almost certainly
acceptable.
To comply with the requirements of EN 60079: 14
Electrical installations design, selection and erection ,
each of the wires entering the hazardous area
should be individually fused and contain a means of
isolation. These two requirements may be satisfied
by using DIN rail mounted terminals incorporating an
easily removable fuse which can be extracted to
achieve isolation as shown in Fig 2. Clear
identification of, and easy access to the means of
isolation is essential for their effective use. It is also
necessary to ensure that the maintenance procedure
makes sure that unauthorised re-closure of the
switches does not occur. It is not considered
necessary to have a means of isolation or electrical
protection for the screen.
Fig 2 DIN rail mounting terminals incorporating a
fuse
For some applications Ex nA instrumentation
energised by a current limited power supply or
instrument that can be switched off, is considered
adequate and to comply with the requirements of the
standard.
4.2 Pulse input
The BA367NE can count and display the total
number of input pulses received from a wide variety
of sensors located in a Zone 2 hazardous area or in
a safe area. Fig 3 shows the connections when the
sensor is located in Zone 2 and Fig 4 the
connections required when the sensor is in a safe
area.
Fig 3 Connections for sensor in Zone 2
Fig 4 Connections for sensor in safe area
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