Chapter 3 Hardware Overview
VXI-MIO Series User Manual
3-8
National Instruments Corporation
Figure 3-2.
Dither
You cannot disable dither on the VXI-MIO-64XE-10. This is because
the ADC resolution 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.
Multichannel Scanning Considerations
All of the VXI-MIO Series modules 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 modules. Refer
to Appendix A,
Specifications
, for a complete listing of settling times
for each of the VXI-MIO Series modules.
When scanning among channels at various gains, the settling times may
increase. When the PGIA switches to a higher gain, the signal on the
previous channel may be well outside the new, smaller range. For
instance, suppose a 4 V signal is connected to channel 0 and a 1 mV
100
200
300
400
0
500
-4.0
-2.0
0.0
2.0
4.0
-6.0
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
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
