BNC 971 Food-SSAFE Analysis Kit - Manual (Page 9)

Food-SSAFE Operation Manual Page 10 of 20
d. Util|Detector Settings opens the Detector Settings
screen. The hardware settings (HV, Threshold, Shaping
Time, Input and Polarity, Coarse Gain, and Fine Gain)
can be modified as needed to make the spectrum display
suit your needs and purposes. The proper settings for
these items were set when the initial calibration and
should generally not be altered. This is because changes
to these hardware settings will dramatically affect
detector response, invalidating any calibrations done so
far. The exception to this is the fine gain, which can be
used to compensate for drift in the spectrum caused by
changes in temperature, etc. Note: A separate function
exists for adjusting the fine gain, covered below under
Util|Fine Gain Adjust.
Tap the OK button to load these settings to the MODEL 970 and update the detector
configuration file. Note: If the high voltage has been changed you will need to wait up to
four seconds (while the MODEL 970 ramps the high voltage to the new setting) before
you can begin a new acquisition.
There can only be one set of parameters for any MODEL 970/detector combination; these
settings are 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, serial number, and/or manufacturer.
Tap the Cancel button to exit the screen without applying any of the changes made.
e. Util|Energy Calibrate opens the Energy Calibration
dialog. The energy calibration has been performed during
the factory setup and calibration. Changing any of these
settings will invalidate that calibration. Instead, use
the fine gain adjustment to compensate for any drift that
has occurred.
In order to perform an energy calibration you should be
displaying a spectrum of a known isotope. The energy
calibration routine involves identifying two or more peaks
and associating the channel numbers with the peak
energies.
To perform an energy calibration check the Allow Edit
box to enable the energy calibration controls.
Next, tap the first peak you know the energy for and a vertical line will appear. Use the
right and left arrow buttons to move the line to the center of the peak—it may also be
helpful to zoom the view. Enter the energy for the peak in the box marked keV:. You
are not limited to whole numbers for energy values.
Use the up arrow to change the energy calibration point to 2. Un-zoom the display by
checking Full and tap the second peak for which you know the energy. Use the left and