What is the differnece between AI 561 (A1) and AI 561 (B4) ...the differnece between the two versions ?
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IMHO the difference is only the FW version.
Probably one of the two units have one improvement of the internal logical, in public ABB library there are not a documents about this.
In the past, I haved one similar case for analog input AI563, at the follow link the old answer
Hope this help you