Sigma BM-286A service manual Settings for Plastic Detectors, Lld, Uld

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5. MAINTENANCE page 36

5.3. DISCRIMINATOR ADJUSTMENT

The Upper and Lower Level Discriminators (ULD & LLD) set the maximum and minimum energy levels at which the system accepts counts. The LLD must be set high enough to prevent system noise from being amplified and counted.

The DOS machine sets the levels on the RCS-120 discriminator card but gets its values from the NT machine.

The upper and lower level discriminators’ adjustment range is 0 keV to approximately 1.5 MeV. These levels are controlled by entering the Utilities Menu and pressing the Detectors, Scale and Disc. button.

The Set Discriminator box and detector counts will appear with the previous upper and lower settings. Using the up and down arrows the values for upper and lower can be changed but are not sent to the DOS machine until the send button is pressed. Observe the counts in the detector boxes to insure you have not reached the lower level noise threshold.

The approximate energy level in keV can be obtained by multiplying the settings by 150. The exact value may vary slightly due to variations in the detectors and electronics. For initial set-up, a good starting point is:

SETTINGS FOR PLASTIC DETECTORS

LLD

=

0.3 volts

=

45 keV

 

 

 

 

 

ULD

=

10.0 turns

=

1.5 MeV

 

 

 

 

 

NOTE:

If either level is changed you must always recalculate all waste stream efficiencies.

The unit will also acquire a new background when leaving the Utilities Menu. Always run a variance after adjusting the levels.

Model BM-286A

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Contents Waste Monitor Model BM-286A Theory of Operation Table of ContentsInspection and Installation MaintenanceRecommended Spare Parts Spare Parts Ordering Information TroubleshootingAppendix Warranty Glossary Formulas Configuration Tracking Sheet PartsScope and Purpose of Manual IntroductionSpecifications Introduction Introduction Inspection Installation General Overview Operating InstructionsPOWER-UP and SELF-TESTS Level One Access Access MenuPCA-II Normal Operation Operating Instructions Programming the System Abcdefgh SET-UP MenuOperating Instructions Operating Instructions Waste Stream Parameters Operating Instructions Operating Instructions Operating Instructions This value is used only when the Alarm Type is set to DPM Utilities Menu Operating Instructions Reports Initial Installation Checklist Operating Instructions BM-286A Waste Stream SET-UP Worksheet Unit Operation Theory of Operation Theory of Operation Theory of Operation Theory of Operation Operator Maintenance Maintenance Maintenance Settings for Plastic Detectors LLDULD Weight Calibration Maintenance Diagnostic Aids Fault Isolation Computers Longs Peak Court LONGMONT, Colorado Appendix B. Glossary Appendix B. Glossary Activity from Counts Reliable Detectable Activity RDA Formula Variance System Modifications Configuration Tracking SheetLongs Peak Court LONGMONT,COLORADO Drawings