Thermo Scientific SAM12, Manual

Page: 142 / 176

Setting Up Procedure Issue: 1.0
9-8 SAM12 User Manual Thermo Fisher Scientific
variance of the counts recorded in each cycle, divided by the
mean count in all the cycles. The upper and lower variance
limits have defaults of 1.5 and 0.67. The default values are
based on a recommended number of counting cycles of 25 and
a cycle period of 25 s. If the number of cycles or the counting
period is increased above these values, then the spread of
values is lower, and the limits may be reduced. Refer to
Figure
11 (page 9-9) for typical limits.
The NBR feature is effectively a pair of filters which examine
the ratio of pulse rates above different pulse height thresholds.
Since the ratios from NORM, and typical man-made radiation
are well known, then a degree of compensation is possible
when NORM is present.
See
Params 3 (page 5-11) to view the setting of the NBR
parameters. This should only be undertaken by an expert user,
and this menu is only available at the Thermo Fisher level (see
Menu Roles (page 5-5) for more information).
These parameters may be fine tined based on the NORM
present on the users site. However it is recommended that the
user receives specific training from Thermo Fisher Scientific,
since incorrect setting of these parameters may result in some
samples being incorrectly identified as NORM.
Setting the NBR
parameters