BEKA BA364G, Руководство пользователя

Страница: 29 / 40

Fig 13 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. Figure 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 summary
When a BA367NE is supplied with alarms the
configuration menu is extended as shown in Fig 14.
For simplicity Fig 14 only shows the configurable
functions on the rate option of alarm AL1, the total
options is identical except that total alarms do not
have hysteresis. Alarm AL2 is identical to alarm
AL1. The following table summarises each of the
alarm configuration functions and includes a cross
reference 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 rate or total display.
See section 9.3.5
5P1r
Alarm setpoint 1
or Adjusts the alarm setpoint. The alarm is
5P1t
activated when the rate or total display
equals the setpoint.
Note:
5P1r
is displayed for a rate alarm
and
5P1t
for a total 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
no . nc
Normally open or normally closed
output.
Determines whether the single pole
alarm output is open or closed in the
non-alarm condition.
See section 9.3.8
H5tr
Hysteresis
Adjusts the alarm hysteresis. Only
available on a rate alarm.
See section 9.3.9
dELA
Alarm delay time
Adjusts the delay between the display
equalling the setpoint and the alarm
output being activated.
See section 9.3.10
S5IL
Alarm silence time
Defines the time that the alarm output
remains in the non-alarm condition
following acceptance of an alarm.
See section 9.3.11
FL5H
Flash display when alarm occurs
When enabled, alternates the rate or
total display between process value and
alarm reference
Al1
or
Al2
when an
alarm output is activated.
See section 9.3.12
AC5P
Access setpoint
Sub-menu that enables direct access to
the alarm setpoints from the display
mode (when BA367NE is counting) and
defines a separate security code.
See section 9.3.13
29