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SDS1000CNL & CML range share nearly the same HW, except the CNL has 40K memory vs 2M for CML.
They both have 1 Gsa/s sampling speed.
Both are 2 channel models.
SDS1000CFL range is quite different, 2 Gsa/s, 4 channels, 24 K memory.
http://www.siglentamerica.com/pdxx.aspx?id=58&T=2&tid=1The sampling capability must be shared between channels and for this reason the CFL has double the sampling to maintain 500 Ks/s with all channels active.
But if only one channel is used the full sampling speed will apply to that channel.
The CML and CNL ranges are the most popular, the additional memory of the CML useful when analysing complex captured waveforms in detail.