Thanks for Contacting National Instruments. Most of our Multifunction DAQ cards follow the same standard for differential inputs, and that is they are in groups of 8, so connecting between ai0 and ai8, and ai1 and ai9 and so on down to ai7 and ai15. This holds for our 32 input and 64 input devices as well. You will notice on your 6020E pinout that ai0 and ai8 are close to each other for this reason. Let me know if I can be of more help on this matter. You can view the pinout in Measurement and Automation Explorer by right-clicking on the device and selecting "Device Pinouts". It is also is in the specifications. Hope this helps
Regards,
Kenn North Principal Product Manager - Search, Digital Analytics http://ni.com/search