Chapter 3 Hardware Overview

National Instruments Corporation 3-7 DAQCard E Series User Manual

You cannot disable dither on the DAQCard-AI-16XE-50. This is

because the ADC resolution is so fine that the ADC and the PGIA

inherently produce more than 0.5 LSB rms of noise. This is equivalent

to having a dither circuit that is always enabled.

Multichannel Scanning Considerations

All of the DAQCard E Series cards can scan multiple channels at the

same maximum rate as their single-channel rate; however, pay careful

attention to the settling times for each of the DAQCards. The settling

time for most of the DAQCards is independent of the selected gain,

even at the maximum sampling rate. The settling time for the high

channel count and very high-speed cards 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

Figure 3-3.

Dither

100 200 300 4000 500
-4.0
-2.0
0.0
2.0
4.0
-6.0
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

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