ORTEC DSPEC Pro, Hardware User Manual

Page: 50 / 108

DSPEC Pro
®
Digital Gamma-Ray Spectrometer User’s Manual 794380D / 0914
40
Enter the ROI Integral preset value in counts. With this preset condition, the MCB stops count-
ing when the sum of all counts in all channels for this MCB marked with an ROI reaches this
value. This has no function if no ROIs are marked in the MCB.
The Uncertainty preset stops acquisition when the statistical or counting uncertainty of a user-
selected net peak reaches the value you have entered. Enter the Preset in % value as percent
uncertainty at 1 sigma of the net peak area. The range is from 99% to 0.1% in 0.1% steps. You
have complete control over the selected peak region. The region must be at least 7 channels wide
with 3 channels of background on each side of the peak. Note that MAESTRO calculates this
preset once per 40 seconds. Therefore, the software will continue data acquisition up to
40 seconds after the preset has been reached, and the uncertainty achieved for a high count-rate
sample may be lower than the preset value.
Use the Start Channel and Width fields to enter the channel limits directly, or click Suggest
Region. If the marker is positioned in an ROI around the peak of interest, Suggest Region reads
the limits of the ROI with the marker and display those limits in the Start Chan and Width
fields. The ROI can be cleared after the preset is entered without affecting the uncertainty calcu-
lation. If the marker is not positioned in an ROI, the start channel is 1.5 times the FWHM below
the marker channel and the width is 3 times the FWHM.
The net peak area and statistical uncertainty are calculated in the same manner as for the
MAESTRO Peak Info command.
Marking the Overflow checkbox terminates acquisition when data in any channel exceeds 2
31
!
1
(>2×10
9
) counts.
2.3.10. MDA Preset
The MDA preset (Fig. 24) can monitor up to 20 nuclides at one time, and stops data collection
when the values of the minimum detectable activity (MDA) for all of the user-specified MDA
nuclides reach the needed value. Presets are expressed in Bq, and are evaluated every
40 seconds. The detector must be calibrated for energy in all spectroscopy applications, and for
efficiency in all applications but MAESTRO.
The MDA presets are implemented in the MCB (i.e., the entries you make on this screen are
saved in the MCB memory), and have no direct link to MDA methods selected in the analysis
options for applications such as GammaVision, ScintiVision™, ISOTOPIC, etc. The MDA
preset calculation uses the following formula: