This is a specially designed expansion for the Duet 2 and Duet 3 family of boards that allows two PT100 temperature sensors to be connected.
For example, Duet2 Wifi and Duet2 Ethernet support up to two daughter boards, with two more on a Duex2 or Duex5 expansion board, with 4 daughter boards for a total of 8 PT100 sensors supported. Expansion for thermocouples and PT100 temperature sensors can be combined and matched.
For thermocouples and temperature sensors see the dedicated section on the website.