SIGMA AM-255 - Manual (Page 24)

APPENDIX B. GLOSSARY page21
Model AM-255
Rolling Background: This is the background accumulation method used in most of TSA’s
instruments. Background accumulation is done in ten separate buffers, each buffer represents
1/10 of the total background time. As each buffer is filled, the background is updated. This
results in a background update at background time/10. Initial background accumulation requires
the full background time.
Standard Background: Standard background requires the full background time for the initial
background and updates.
ULD: The Upper Level Discriminator provides a threshold, usually adjustable, that determines
the highest signal level that will be accepted as a nuclear pulse by the system’s electronics. Also
see LLD.