BEKA BA314NG, Manual

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Fig 13 Equivalent circuit of each alarm output
9.3.2 Ex nA certification
Each alarm output is a separate galvanically isolated
Ex nA circuit with the following input parameters:
Ui = 30V dc
Ii = 200mA
This allows each alarm output to switch any dc circuit
providing that in normal operation the maximum
supply voltage is not greater than 30V dc and the
switched current is not greater than 200mA.
Providing that the BA314NG Tachometer is correctly
installed in Zone 2 the two alarm outputs may be used
to switch suitably protected equipment located in Zone
1 or 2 of a hazardous area, or equipment located in a
safe area.
Fig 14 shows a typical application in which a
BA314NG Tachometer is mounted in Zone 2 is
displaying the output from a Flameproof Ex d 2-wire
proximitor located in Zone 1. Alarm 1 is switching an
Ex e sounder in Zone 1 and alarm 2 is switching a
sounder located in the safe area.
Fig 14 Typical alarm application
(Shown without recommended screened cables)
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 are frequently
satisfied by using fuse holders with easily removable
fuses and removing the fuses to achieve isolation.
This is a satisfactory method at the low voltages and
currents common in instrumentation systems. 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 illustrates an
example of this type of fused terminal block.
For some application Ex nA instrumentation
energised by a current limited power supply or
instrument that can be switched off, is often
considered adequate and to comply with the
requirements of the standard.
9.3.3 Configuration and adjustment
When a BA314NG is supplied with alarms the
configuration menu is extended as shown in Fig 15
which for simplicity only shows alarm AL1 configured
to operate as a speed alarm. The run-time options
are identical except that a run-time alarm can not
have hysteresis. Alarm AL2 functions are identical
to alarm AL1.
The following table summarises each of the alarm
configuration functions and includes a cross
references to more detailed information. Again only
the functions on alarm AL1 are listed.
Display Summary of function
EnbL
Alarm enable
Enables or disables the alarm without
changing the alarm parameters.
See section 9.3.4
tYPE
Type of alarm
Defines whether the alarm operates on
the speed or run-time display.
See section 9.3.5
5P1.5peed
Alarm setpoint 1
or Adjusts the alarm setpoint. The
5P1.Hour5s
alarm is activated when the speed or
run-time display equals the setpoint.
Note:
5P15
is displayed for a speed
alarm and
5P1H
for a run-time alarm.
See section 9.3.6
HI . LO
Alarm function
Defines whether the alarm has a high or
low function.
See section 9.3.7
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