What the ratings mean
The 3ADT218521S0121: The 3 analog inputs and 2 analog outputs give you enough channels for speed reference, current feedback, and a spare for process trim or torque limit. The IP00 rating on auxiliary terminals means the converter itself is open-frame — it needs to live inside a panel or enclosure that provides the final ingress protection. Operating humidity spans 5 to 95% non-condensing, which covers most indoor industrial environments, but check for condensation risk if the cabinet sees rapid temperature swings near a washdown zone.