Is there a data logger that would be compatible with this system that is calibrated for ultra low freezer? If so, can a 3rd data logger be added to the gateway, in addition to the two included in this set?

While we don’t offer it as a kit you could buy as many of the CX405-RTD loggers (intended for ultra-low temp freezers) and add a single gateway.

Here are links:

Logger - https://microdaq.com/onset-intemp-bluetooth-2channel-dry-ice-rtd-temperature-data-logger.php

Gateway - https://microdaq.com/onset-intemp-cx5000-cx-gateway.php

You can also mix and match the loggers within the CX line.