17
9. ACCESSORIES
9.1 Scale card
The BA327C and the BA328C have a window on
the right hand side of the display to hold a card
showing the units of measurement e.g.
o
C, mBar,
RPM. Indicators can be supplied with a printed
scale card showing any units specified at the time
of ordering. If a printed scale card is not
requested, a blank card will be supplied.
Scale cards can easily be marked on site as
follows:
a.
Remove the rear terminal block and the rear
panel as shown in Fig 7.
b.
Carefully pull the indicator assembly from the
enclosure.
c.
Gently pull and then slide the blank scale
card towards the display window until it is
free. Mark the card with the required legend
and replace in the slot.
9.2 Tag strip
Instruments can be supplied with a thermally
printed tag number on the rear panel. This tag
number is not visible from the front of the
instrument after installation.
9.3 Alarms
The BA327C and the BA328C can be supplied
with two solid state single pole alarm outputs which
may be independently programmed as high or low
alarms with normally open or normally closed
outputs. Fig 8 illustrates the conditions available
and shows which are fail safe, i.e. in the alarm
condition the output is open.
WARNING
These alarms outputs should not be
used for critical safety applications such
as an emergency shut down system.
When an alarm is activated the indicator display
alternates between the measured value and an
alarm identification.
Fig 8 Alarm outputs
Programmable functions for each alarm include
adjustable setpoint, hysteresis, alarm delay and
alarm accept.
9.3.1 Solid state output
Each alarm has a galvanically isolated single pole
solid state switch output which is shown in Fig 9.
The output is polarised and current will only flow in
one direction.
Fig 9 Equivalent circuit of each alarm output
9.3.2 Intrinsic safety
Each alarm output is a separate galvanically
isolated solid state switch which has been certified
as simple apparatus. This allows the alarm
terminals 8 & 9 and 10 & 11 to be connected to
any intrinsically safe circuit protected by a Zener
barrier or galvanic isolator providing the output
parameters of the circuit do not exceed:
Uo
=
28V dc
Io
=
200mA
Po
=
0.85W
