ORTEC DSPEC Pro, Руководство пользователя по оборудованию

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794380D / 0914 2. GETTING STARTED
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Figure 23. DSPEC Pro Presets Tab.
2.3.9. Presets
Figure 23 shows the Presets tab.
MDA presets are on a separate tab.
The presets can only be set on an
MCB that is not acquiring data
(during acquisition the preset field
backgrounds are gray indicating
that they are inactive). You can use
any or all of the presets at one time.
To disable a preset, enter a value of
zero. If you disable all of the presets,
data acquisition will continue until
manually stopped.
The values of all presets for the
currently selected MCB are shown
on the Status Sidebar. These values do not change as new values are entered on the Presets tab;
the changes take place only when you start the next acquisition or Close the Properties dialog.
When more than one preset is enabled (set to a non-zero value), the first condition met during
the acquisition causes the MCB to stop. This can be useful when you are analyzing samples of
widely varying activity and do not know the general activity before counting. For example, the
Live Time preset can be set so that sufficient counts can be obtained for proper calculation of
the activity in the sample with the least activity. But if the sample contains a large amount of this
or another nuclide, the dead time could be high, resulting in a long counting time for the sample.
If you set the ROI Peak preset in addition to the Live Time preset, the low-level samples will
be counted to the desired fixed live time while the very active samples will be counted for the
ROI peak count. In this circumstance, the ROI Peak preset can be viewed as a “safety valve.”
Enter the Real Time and Live Time presets in units of seconds and fractions of a second. These
values are stored internally with a resolution of 20 milliseconds (ms) since the MCB clock
increments by 20 ms. Real time means elapsed time or clock time. Live time refers to the amount
of time that the MCB is available to accept another pulse (i.e., is not busy), and is equal to the
real time minus the dead time (the time the MCB is not available).
Enter the ROI Peak count preset value in counts. With this preset condition, the MCB stops
counting when any ROI channel reaches this value unless there are no ROIs marked in the MCB,
in which case that MCB continues counting until the count is manually stopped.