Can the Freezer Tag Be used to monitor ultra cold Freezer temps?

This version of the Fridge-Tag2L is only designed for regular freezer applications. For ultra-low temp freezers you should look at the Fridg-Tag2L-Ultra-Low - https://microdaq.com/berlinger-fridge-tag2-ultra-low-vaccination-system.php Some key differences between the two loggers is that the ultra-low version needs to be calibrated and have its sensor replaced annually. It can be used until the battery dies which is typically 2-3 years.