If you know the limits of your channel readings, you can set these in AI Hardware Config. Take a look at this VI to see the ins and outs of it, but basically you can use it to specify the limits on the channels in your acquisition. Therefore, you can keep a database of the signals you are acquiring and keep the high and low limits for these signals. You can supply these to the AI Hardware Config VI and it will generate the gains and you can actually read these from the VI also. This way, you can check to see if they are what you want and change them if desired.
J.R. Allen