LogTag® products support a feature called pre-start logging, which can be selected during configuration.

When pre-start logging is enabled, the logger will automatically start recording as soon as configuration is completed. It will record at the sampling interval defined during configuration and will continue to record until the user starts the logger by pressing the START button. Once the logger has been started, it will record started readings. While the logger is recording pre-start readings the Alert LED will not activate, even if an alert condition is present, no PDF is produced for USB PDF loggers when plugging into USB and when downloaded to LogTag Analyzer, the report tab will not be available.

Pre-start logging is useful as a fail-safe recording setting so if the logger is not started at the appropriate time, the readings will still be available to view later, albeit without the alerting functionality.

When the readings are retrieved from the logger, any pre-start readings will be separately displayed, so the user can quickly identify the readings recorded before and after the logger was started.

All LogTag® products have a finite amount of memory to store the readings they records. Therefore, while the logger is recording pre-start readings the LogTag® will operate in continuous operation. In this mode,  the oldest pre-start reading will be overwritten with the latest pre-start reading once the logger's memory is full, or the latest started reading if the logger has been started.

Once started, the logger will first fill any remaining memory, then overwrite the oldest pre-start readings until the complete memory is filled with started readings.

If a logger was configured to start recording at a certain date/time, or for push button start from hibernation, no pre-start readings will be recorded. If you configure a logger with a start delay and have pre-start logging enabled, pre-start readings will also be recorded during the start delay.