Echelon LonPoint Application and Plug-In - Manual (Page 172)

13-6 Data Logger Functional Block
Low Threshold This threshold will only be used if the Log Low
option is selected. Only data that is less than or equal
to the value in this field will be logged. Upon crossing
this threshold data is logged once more after the
value crosses back from the threshold. This way the
point at which a value returned from an out of limits
condition will be recorded.
High Threshold This threshold will only be used if the Log High
option is selected. Only data that is greater than or
equal to the value in this field will be logged. Upon
crossing this threshold data is logged once more after
the value crosses back from the threshold. This way
the point at which a value returned from an out of
limits condition will be recorded.
Delta Data is logged when the difference between the last
point entered into the log is greater than or equal to
the value entered.
For example, if you want to log data points between 75.0 and 150.0, select the
Log High and Log Low options, set the Low Threshold field to 150.0, and the
High Threshold field to 75.0.