Chapter 2 Theory of Operation
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National Instruments Corporation 2-15 PCI E Series RLPM
Program SI for 100 µs, SI2 for 10 µs. Figure 2-10 shows the timing
sequence for two scans.
Figure 2-10. Multirate Scanning of Two Channels
This sequence of two scans is repeated 25 times to complete the acquisition.
Notice that channel 0 is sampled once every 100 µs. Hence, its sampling
rate is 10 kS/s, whereas channel 1 is sampled once every 200 µs. Its rate is
5 kS/s. Similarly, you could implement any 1:x ratio of sampling rates. The
effective scan interval of the slower channel will be at the rate of the
faster channel. This implementation requires x scan sequences in the
configuration memory.
Also, you can implement a 1:1:x or 1:x:mx ratio for three channels, where
m is a non-negative integer. Figures 2-11, 2-12, and 2-13 show timing
sequences for different ratios. In these figures, the numbers above the
CONVERT pulses indicate the channels sampled in that conversion.
Figure 2-11. Multirate Scanning of Two Channels with 1:
x
Sampling Rate
START
STOP
CONVERT
Channel 0Channel 0 Channel 1
Sampling Rate
Channel 0: Channel 1 = 2:1
1
x
---
0
0
00
001
START
CONVERT
STOP
Sampling Rates
Channel 0: Channel 1 = 5:1
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