I have had some problems with long term drifts (several hour time scale) of the analog outputs of my PCI-6733. To fix this, I plan on using the AO External Reference pin on the card to supply a more stable reference. Also, I'll be using something like 3V to decrease the size of 1 LSB and reduce sensitivity to noise on the card. My question is, should the stability of the external reference translate directly to the stability of the out outputs? Or is there something internal to the card that might limit this performance? Also, what is the input impedance of the AO External Reference? Finally, is it possible to use the external reference on only some analog outputs but not on all? And if so, how do you implement this? Thanks for the help in advance!