National Instruments AT E Series - Manual (Page 37)

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
100 200 300 400 0 500
–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
100 200 300 400 0 500
–4.0
–2.0
0.0
2.0
4.0
–6.0
6.0
100 200 300 400 0 500
–4.0
–2.0
0.0
2.0
4.0
–6.0
6.0
100 200 300 400 0 500
–4.0
–2.0
0.0
2.0
4.0
–6.0
6.0