SAM III Series | Why is operation in the “Variable Alarm Mode” preferred and why is Auto Variable Trigger employed?

When using the Variable Alarm Mode (as opposed to Fixed Alarm Mode) a low threshold can be set to start the acquisition during a search for radionuclides.  A low threshold which triggers the start of an acquisition is important for achieving high sensitivity.  However, changes in the background during surveillance can cause false triggers that may result in false identification of isotopes.  To prevent false triggers from happening BNC uses a scheme called “Auto Variable Trigger”. This is a threshold adjustment that continuously optimizes the threshold setting automatically.  Those performing environmental surveillance will find this mode especially valuable as it allows identification of NORM isotopes with the highest sensitivity possible during changes in NORM.