Sigma BM-286A service manual Diagnostics and Utilities, Utilities Menu

3. OPERATING INSTRUCTIONS page 22

3.5. DIAGNOSTICS AND UTILITIES
When the operator presses the utilities button, the	UTILITIES MENU
operator will be presented with the Utilities Menu.
	Variance
	Scale Reset
Press the appropriate button from the menu as shown.
	Detector Efficiency Check
The functions are as follows:
	Operator Set-up
	Shut Down
3.5.1. Variance:
	OK
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.

Model BM-286A