If the common mode voltage range is 20-40VDC, will there be any changes in
offset errors at these ranges since device is specified at common mode voltage
of 4? If there will be changes pl advice by how much and in what parameters?
If the common mode moves, the offset will stay within the specified range, but
voltage at the output will be affected. This is because of the CMRR. Here is a
detailed explanation of how CMRR affects the error at the output.
Additionally, here is a link explaining in detail how the input offset is
related to output error for a current sense part like the AD8218.