Memory Mode Selection will be grayed-out if not in Linear sampling mode. When using a Levelogger in Linear Mode, there is a choice of Continuous Logging (wrap around) or Slate logging .
Compressed Linear, Event-based and Schedule sampling modes can only use the Slate Mode option.
In Continuous logging the new log is started at the end of any previous log and continues logging, eventually recording over the first logged data. As one of the download options is to 'Append Data', Continuous logging can be a preferred choice when logging long-term.
In Slate logging the new log is also started at the end of any previous log, but will stop recording after 40,000 readings (or up to 120,000 readings), so that the beginning of the current log will not be written over.
Figure 5-13 Datalogger Memory Mode
(Click image to enlarge to full size)
Table of Contents
or Slate logging 
. 