<i>how am i wasting 2 bits. </i> By using only one fourth of the input range, you are in effect throwing away two bits (2^2 = 4)
<i>since the full scale voltage reading is 0 to 5 volts then should it not be 5/2048 resolution.</i> But you said the resolution of the CARD was +/- 10 Volts. The card doesn't know that you're only connecting a 0-5V signal to it. If it's configured to measure +/- 10V, then that's what it will do. Half of your measurement range is wasted because your signal can't be negative. Half of the remainder is wasted because your signal can't be above 5 Volts. <i>although i may be wasting 1/4 of the scale </i> You are wasting THREE fourths. <i>but is it having an effect on the calculation as the calculations look the same even when the signal goes from 0 to 5.</i> No - that's my point. The calculations will be the same, regardless of whether your signal goes from 0 to 5V or 0 to 10 V or -10 to 10 V. It's the range of the CARD divided by the number of different values that the CARD produces. In your case this is 20 V divided by 2^11 = 0.009766 V. If that's not clear, keep asking.
