BNC 971 Food-SSAFE Analysis Kit - Manual (Page 10)

Food-SSAFE Operation Manual Page 11 of 20
right arrows to adjust the location of the line to the center of the second peak, and then
enter the energy. Repeat this process for up to 12 energy calibration points.
Note: It is not strictly necessary to enter the calibration points in any order. When the
energy calibration is performed the calibration points will be sorted in order of the
channel values, from lowest to highest.
When all energy calibration points have been entered, tap the Do Energy Calibration
button. A summary of the channels and associated energy values will be displayed in the
list box. Review these for accuracy, as out-of-order values will cause strange results in
later analyses.
The energy calibration is not actually stored and made active until the OK button is
tapped. If the Cancel button is tapped any new values entered will be lost.
The Load button can be used to load a stored spectrum into the Spectrum Display.
When Allow Edit is not checked, it is still possible to use the up and down arrow buttons
to scroll through the energy calibration settings.
This screen can, of course, also be used to edit any existing energy calibration. There can
only be one energy calibration for any MODEL 970/detector combination. The energy
calibration is loaded following the selection of the detector to use at program startup.
You can force a single detector to have multiple settings by creating a new detector and
changing the description. When in Offline mode, however, the energy calibration stored
in the detector file (.usf) will be applied each time a new spectrum file is loaded. This
does not occur when not in Offline mode.
f. Util|Manual Fine Gain Adjust opens the Manual Fine
Gain Adjustment screen. An energy calibration must be
performed before this function can be used (see below).
The fine gain adjustment is intended to provide an easier
way to compensate for energy drift in the detector
(typically caused by temperature changes) than using the
Detector Settings screen.
Use the Start, Stop, and Clear buttons as on the Main
Screen. Acquire a spectrum of a known source and select
the isotope from the dropdown list. This will cause the
library energies for that isotope to be displayed on the
spectrum. Checking Full Height will cause the lines to
extend to the full height of the display instead of being
proportional to the abundance. If the energy line does not match up with the peak,
increase or decrease the fine gain control a little bit and tap the Set Fine Gain button.
Then Clear the spectrum and begin another acquisition. Repeat this until the vertical line
and peak line up with one another.
Tap the OK button when the fine gain adjustment is complete or tap Cancel to revert to
the original fine gain.