SIGMA BM-286A - Manual (Page 25)

3. OPERATING INSTRUCTIONS page 22
Model BM-286A
3.5. DIAGNOSTICS AND UTILITIES
When the operator presses the utilities button, the
operator will be presented with the Utilities Menu.
Press the appropriate button from the menu as shown.
The functions are as follows:
3.5.1. Variance:
The Variance program implements an algorithm to
compute the statistical accuracy of counts obtained
from each of the six plastic detectors in the system. The number of passes run by the program,
and the sample time for each pass, are user selectable from the Set-Up Menu.
(TSA generally recommends three passes of 60 seconds each.)
At the end of each pass, four columns of information are displayed for each detector. The
columns contain, from left to right, the mean counts, the variance in counts (S2), the variance to
mean ratio (R), and the mean value of R. Readings in the third column (R) should not exceed
0.49. TSA’s normal acceptance criterion is that, for the third pass, no detector should show a
mean value of R (fourth column) greater than 0.30.
The results of each iteration are displayed and held until the results of the next iteration are
available. The results of the final iteration are held until the operator presses OK.
3.5.2. Scale Reset:
This tool allows the operator to reset the scale controller if a problem is suspected. This process
will take approximately 30 seconds and a message will be displayed during the operation.
UTILITIES MENU
Variance
Scale Reset
Detector Efficiency Check
Operator Set-up
Shut Down
OK