Chapter 2
Installing and Configuring the DAQPad-MIO-16XE-50
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National Instruments Corporation
2-7
DAQPad-MIO-16XE-50 User Manual
reduces measurement noise, resulting in improved resolution. Dither, or
additive white noise, has the effect of forcing quantization noise to become
a zero-mean random variable rather than a deterministic function of the
input signal.
Figure 2-2 illustrates the effect of dither on signal acquisition. Figure 2-2a
shows a small (±4 LSB) sine wave acquired with dither off. The
quantization of the ADC is clearly visible. Figure 2-2b shows what happens
when 50 such acquisitions are averaged together; quantization is still
plainly visible. In Figure 2-2c, the sine wave is acquired with dither on.
There is a considerable amount of noise quantization. Dither has the effect
of forcing quantization noise to become a zero-mean random variable
rather than a deterministic function of the input signal.
Figure 2-2.
Dither
100
200
400
a. Dither disabled; no averaging
b. Dither disabled; average of 50 acquisitions
c. Dither enabled; no averaging
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400
0
500
–4.0
–2.0
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2.0
4.0
–6.0
d. Dither enabled; average of 50 acquisitions
LSBs
LSBs
LSBs
LSBs
6.0
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400
0
500
–4.0
–2.0
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2.0
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–6.0
6.0
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500
–4.0
–2.0
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–6.0
6.0
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500
–4.0
–2.0
0.0
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–6.0
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