I had the same question, with the same ADAM-6017 IO module and found a solution.
It is possible that this solution did not exist at the time of the original post back in 2012 but I thought I’d post the current solution for others like me who come across this post looking for answers.
The solution is to use “Holding Registers with 16 bit unsigned integer conversion” as the modbus type with the Ignition OPC-UA Server…
Examples:
Change OPC Item path from:
[{DeviceName}]1.HR4
to:
[{DeviceName}]1.HRUS4
For modbus address mapping change Modbus Type from:
Holding Register (Int16)
to:
Holding Register (UInt16)
Reference:
https://docs.inductiveautomation.com/display/DOC/About+Modbus+Addressing