Network Card User Manual

Chapter 3 Hardware Overview
© National Instruments Corporation 3-11 AT E Series User Manual
Figure 3-7. Dither
You cannot disable dither on the AT-MIO-16XE-10, AT-AI-16XE-10, or
AT-MIO-16XE-50. This is because the resolution of the ADC is so fine that
the ADC and the PGIA inherently produce almost 0.5 LSB
rms
of noise. This
is equivalent to having a dither circuit that is always enabled.
Multiple-Channel Scanning Considerations
All of the AT E Series devices can scan multiple channels at the same
maximum rate as their single-channel rate; however, you should pay
careful attention to the settling times for each of the devices. The settling
time for most of the AT E Series devices is independent of the selected
gain, even at the maximum sampling rate. The settling time for the high
channel count and very high-speed devices is gain dependent, which can
affect the useful sampling rate for a given gain. No extra settling time is
necessary between channels as long as the gain is constant and source
impedances are low. Refer to Appendix A, Specifications, for a complete
listing of settling times for each of the AT E Series devices.
100 200 400
a. Dither disabled; no averaging b. Dither disabled; average of 50 acquisitions
c. Dither enabled; no averaging
100 200 300 4000 500
–4.0
–2.0
0.0
2.0
4.0
–6.0
d. Dither enabled; average of 50 acquisitions
LSBs
LSBs
LSBs
LSBs
6.0
100 200 300 4000 500
–4.0
–2.0
0.0
2.0
4.0
–6.0
6.0
100 200 300 4000 500
–4.0
–2.0
0.0
2.0
4.0
–6.0
6.0
100 200 300 4000 500
–4.0
–2.0
0.0
2.0
4.0
–6.0
6.0