baseline offset in FC500

Alan Bishop alan.bishop at imvs.sa.gov.au
Wed Jun 20 20:41:36 EDT 2007


Li

do not use 'baseline offset' whilst collecting data.  The 'baseline offset'
algorithm will work against your voltage adjustments as you make them - it
is possible to be fooled into bringing your voltage down so afar as to make
positive and negatives look exactly alike!

If you want to use the 'baseline offset' to make your data look "pretty"
then do so post acquisition. All the algorithm does is to take 'zero' off
axis events and place them in the first decade as a "pretty" gaussian.

'Baseline offset' is recorded as a flag setting in the file header to tell
the application whether to use the 'baseline offset' algorithm or not.
'Baseline offset' is still selectable post acquisiton and during any
subsquent analysis. However if you use 'baseline offset' during acquisiton
you may set your fluorescence gains incorrectly and collect incorrect data.
You can toggle it on and off whilst setting up to see what your results can
look like when it is on but I seriously recommend you leave it off for
actual acquisition.  It is a very dangerous toy, I have had several users
destroy their data using this function incorrectly even after they were
warned not too. I have a large warning sign on all our Beckman Coulter flow
cytometers NOT to use the 'Baseline Offset' during acquisition.

Beckman Coulter have provided a liitle information about 'baseline offset'
in the CXP help file under Workspace Preferences - Plot Display - Baseline
Offset. Its probably in a similar place with Expo32.

Alan

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E-mail:alan.bishop at imvs.sa.gov.au
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	    Senior Flow Cytometrist
	    Detmold Flow Cytometry Facility
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> -----Original Message-----
> From: chen li [mailto:chen_li3 at yahoo.com]
> Sent: Wednesday, 20 June 2007 03:29
> To: Cytometry Mailing List
> Subject: baseline offset in FC500
>
>
> Dear all,
>
> I just wonder what the purpose of baseline offset is
> in FC500. What are the differences between using and
> without using this feature when collect Flow data?
>
> Thanks,
>
>
> Li
>
>
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