Akeeg,
Thanks for the setup information. How are you measuring this device to see that you have an offset? Additionally, what kind of connecters are you utilizing (it shouldn't make a difference but it would be good to know)
If you would like National Instruments to research this further for the internal circuitry of the device, it would be best to create a service request at http://www.ni.com/support because we would need to go through a process to see if hardware information can be released. You are always open to keep this discussion post open in case anybody else in the community has any other input.
Regards,
Ali S.
Applications Engineering
National Instruments