Chapter 3 Hardware OverviewVXI-MIO Series User Manual3-8 National Instruments CorporationFigure 3-2. DitherYou cannot disable dither on the VXI-MIO-64XE-10. This is becausethe ADC resolution is so fine that the ADC and the PGIA inherentlyproduce almost 0.5 LSB rms of noise. This is equivalent to having adither circuit that is always enabled.Multichannel Scanning ConsiderationsAll of the VXI-MIO Series modules can scan multiple channels at thesame maximum rate as their single-channel rate; however, you shouldpay careful attention to the settling times for each of the modules. Referto Appendix A, Specifications, for a complete listing of settling timesfor each of the VXI-MIO Series modules.When scanning among channels at various gains, the settling times mayincrease. When the PGIA switches to a higher gain, the signal on theprevious channel may be well outside the new, smaller range. Forinstance, suppose a 4 V signal is connected to channel 0 and a 1 mV100 200 300 4000 500-4.0-2.00.02.04.0-6.0LSBsLSBsLSBsLSBs6.0100 200 300 4000 500-4.0-2.00.02.04.0-6.06.0100 200 300 4000 500-4.0-2.00.02.04.0-6.06.0100 200 300 4000 500-4.0-2.00.02.04.0-6.06.0a. Dither disabled; no averaging b. Dither disabled; average of 50 acquisitionsc. Dither enabled; no averaging100 200 300 4000 500-4.0-2.00.02.04.0-6.0d. Dither enabled; average of 50 acquisitionsLSBsLSBsLSBsLSBs6.0100 200 300 4000 500-4.0-2.00.02.04.0-6.06.0100 200 300 4000 500-4.0-2.00.02.04.0-6.06.0100 200 300 4000 500-4.0-2.00.02.04.0-6.06.0
