BEKA BA317NE, Manual

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9.3 Display backlight
The BA317NE Tachometer can be supplied with a
factory fitted backlight that produce green illumination
enhancing display contrast and enabling the display to
be read at night and in poor lightng
conditions. The optional backlight is internally
powered from the instrument power supply so that no
additional wiring is required, but the supply current
increases as shown below:
Without backlight 10.0mA
Addition for backlight 22.5mA
Addition with terminals 3 & 4 linked 6.0mA
_______
Total current 38.5mA
9.4 Alarms
The BA317NE can be supplied with factory fitted
dual, solid state, single pole alarm outputs that may
be independently configured as high or low, speed or
run-time alarms with normally open or normally
closed outputs.
Note: Only one of the three output options can be
fitted.
Configurable functions for each alarm include
adjustable setpoint, alarm delay time and alarm
silence time. Hysteresis may be applied to speed
alarms.
CAUTION
Alarm outputs should not be used for
critical safety applications such as a shut
down system.
When the BA317NE Tachometer power supply is
turned off or disconnected, the alarm outputs will
open irrespective of whether normally open or
normally closed outputs have been selected. When
designing a system an open output should therefore
be chosen for the alarm condition.
Alarm annunciators on the instrument display
indicate the status of each alarm. If an alarm delay
or silence time has been selected the annunciator
will flash during the delay or silence period.
The BA317NE internal counters are up-dated and
compared with the alarm setpoint twice per second,
irrespective of the display update time selected.
This may result in an alarm being delayed for up to
half a second after the speed or run-time has
exceeded the setpoint.
9.4.1 Solid state output
Each alarm has a galvanically isolated single pole
solid state switch output as shown in Fig 12. The
outputs are polarised and current will only flow in
one direction. Terminals A1 and A3 should be
connected to the positive side of the supply.
Ron = less than 5

+ 0.7V
Roff = greater than 1M

Note: Because of the series protection diode some
test meters may not detect a closed alarm
output.
Fig 12 Equivalent circuit of each alarm output
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