Figure 2-14. Multirate Scanning Without Ghost; Figure 2-16. Successive Scans Using Ghost - National Instruments PCI E Series Programmer's Manual

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Figure 2-14. Multirate Scanning without Ghost

In Example 3, channel 0 is sampled correctly. Although channel 1 is
sampled twice, it does not yield a 50% duty cycle. This type of acquisition
will result in imprecise rates. Figure 2-15 shows the relative occurrences of
convert pulses in Figure 2-14.
Channel 1, Example 3
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Figure 2-15. Occurrences of Conversion on Channel 1 in Example 3
To rectify the problem, use ghost as illustrated in Figure 2-16.
0 1 0 1

Figure 2-16. Successive Scans Using Ghost

The shaded conversions are ghost conversions. The short arrows indicate
channel 0 samples and the long arrows indicate channel 1 samples that are
actually stored in the FIFOs.
Sampling Rates
Channel 0: Channel 1 = 3:2
t
1 0
0
t 2t
0 1 0 1
2-17
Chapter 2 Theory of Operation
t
0
1
t
0 1
0 1
PCI E Series RLPM