Hey Saeed,
It seems to me that you probably have other modules in your SCXI chassis. The -10740 error usually refers to an issue that can occur if the modules are not inserted in the proper order.
If you refer to the following knowledge base, this error is discussed.
http://digital.ni.com/public.nsf/websearch/91C7DE7A2C2C9AC586256A0A001D8B5D?OpenDocument
Also, if you refer to the following knowledge base, the proper module order is discussed.
http://digital.ni.com/public.nsf/websearch/86256A47004E16D186256B4B0051B3AA?OpenDocument
Finally, in this situation, I would hook up just the SCXI-1520 in the left most slot of the chassis and see if that will allow you to assign an excitation voltage in MAX (Measurement & Automation that works.
Just let us know if thi
s does not take care of the issue.
Thanks,
Justin Tipton
National Instruments