10.2 Dead
calibration
for the various samples and the status
messages. Figure 11 shows the display when
this routine is first entered. The meaning of
the lines are described below.
.
The dead time calibration routine is used
to calculate the dead time of the
and
the detector. The minimum dead time will be
about
due to the signal conditioning
circuitry. This routine uses the
method for calculating the dead time. The
background count is taken then source 1 is
counted, then
1 and source 2 are
count&
then
source
2
is counted. After these
counts are taken, the dead time is calculated.
When the dead time calibrate routine is
started, the current dead time is saved and the
dead time is then automatically set to 0. When
the routine is finished, the user has the choice
of using the new dead time or the dead time
that was used before the routine was
To achieve
results, the following
conditions need to be met.
Ibis line displays
which sample is
.
SAMPLE1
‘Ibis line displays
0
the bar graph
0
ratemeter.
11.
l
Display.
and 4:
These lines
used to display the count time when a
count is in progress.
l
5: This line displays the back-
ground count.
o Have the background as low as
possible.
0 Use sources of approximately equal
l
displayed here.
l
and sample 2 is displayed here.
0 The
count rate from both
sources needs to be high enough to
provide about 10% to
dead time
losses.
l
displayed here.
0 When moving the sources, make
sure the stationary source is not touched or
moved as small changes in the source
position could cause errors.
Keep the
enough
shielded enough from the detector to not
cause significant background changes.
W h e n t h e
background count
6SECONDS
play changes to
COUNTING
that shown in
0
12. The
time will
count down to 0
The use of the dead time calibrateroutine
is explained below. This will show the
displays and describe the functions. The dead
time calibrate display is only displayed
this routine is enabled. The bar graph
ratemeter is displayed along with the counts
while the back-
ground count is
A t t h e
end of the count
time, the count time lines will be cleared and
the top line of the display will read ‘SAMPLE
1’.
this count is
the top line
will then read ‘SAMPLE
After this count
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