256 vs. 1024 channels
Peter Van Osta
pvosta at unionbio-eu.com
Wed Mar 20 03:40:44 EST 2002
My main expertise is on microscopy, but the rules for sampling are more
or less the same for linear as for N-dimensional signals. The "sampling"
rate you need, either 1024 or 256 is determined by the "resolution" you
need to distinguish adjacent "peaks". The Nyquist sampling rate is the
rule to apply to a signal and it says that you have to sample any signal
at twice the "frequency" of the signal you are studying. So you have to
chose the appropriate sampling rate for the signal/object you want to
I have created a webpage which illustrates the Nyquist sampling
principle for microscopy (2D).
If you want to quantify the size/dimension of the peaks, the Nyquist
sampling theorem alone is not enough. The smaller the peak, the higher
the resulting C.V. (Coefficient of Variation) in the sampled signal.
Professor Ian T. Young from the T.U.Delft explained this in a paper,
which is also avaialable on-line.
Dr. Peter Van Osta
Union Biometrica N.V./S.A.
European Scientific Operations (ESO)
tel.: +32 (0)14 570 619
fax.: +32 (0)14 570 621
> At 13:57 18/3/2002, Calman Prussin wrote:
> >Several years back when we were analyzing large numbers of events on G1
> >Power PC Macs, I started doing our data collections using 256 channels,
> >rather than the typical 1,024. The speed of analysis was increased
> >markedly with this change.
> >Common sense tells me that there should be little if any difference in the
> >data generated using either 256 or 1024 channels. Perhaps my histograms
> >will look a little smoother?
> >Question: What real advantage is there to using 1024 rather than 256
> >channels? Does it add significantly to the precision of DNA, CFSE or CBA
> >assays? For less exacting applications (phenotyping, intracellular
> >cytokines) is there any real benefit?
> >Thanks, Calman
> Joseph Webster, Flow Cytometry Facility
> Centenary Institute, Sydney, AUSTRALIA.
> Phone +61-2-9565-6110
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