IIM board (Input Interface Module)

[techzone12]

When wiring input sensors as inputs to digital controllers, I sometimes see that a "IIM board" being used. My understanding is that they are used for electrical isolation between field devices and the controller.

My question is , when is it a must, and when is it an option? Or is it an extra protection (i.e you don't necessarly have to have it)?

Thanks

 

[dV8r]

Only the designer can accuratly answer this question. Or someone with ALL of the information that a designer would need.