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Fire safety pin
Temperature
measuring device
for source air
column
Receiver component
Component
Receiver
High voltage bias
supply
Ion Chamber
Force capsule to
retract in event of
high temperature
condition
Measure the air
temperature in the
air space between
the source capsule
and the head
window
Function
Provides -350 VDC
ion chamber bias
Converts beta flux
to current for
conversion in
detector amplifier
Activated by
temperatures
exceeding 500
degrees F
5 – 24 VDC
Power Req's
On detector back-
plane
none
Check if rod still
attached to housing
by solder. Try to
move actuator with
source in head by
manually lifting
and lowering
mechanical
indicator flag
Backplane Tp5 –
Tp6
Test point
Check test points
on receiver
backplane. The ion
chamber output is
rather insensitive to
changes of a few
volts of bias
although in general
bias voltage is
stable to within a
volt
Physical inspection
of ion chamber and
casting
3. Solenoid can
overheat and
jam
1. May creep
(slowly
move under
pressure)
2. May
inadvertently
activate
Physical damage
Failure modes
Output voltage goes
to nearly zero volt
is most common
failure mode
Gas leak,
intermittent short
between ion
chamber and
housing. This can
induce a down
going spike in
sensor output
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