Marcus - Documenting the conditions under which an experiment is run is a always a good idea, but it is necessary to understand its use. Primarily, especially in conjunction with a well understood standards such a bead, the settings can help someone who knows the flow instruments at a particular site determine whether problems with experimental data are due to instrument problems or sample problems. Secondarily, these settings will allow an instrument user to recreate the conditions under which previous data were run. Because of alignment changes between runs, the instrument usually will not give the same results, but will be a good starting place for setup. And thirdly, knowledgeable users at other sites may also use these settings as starting points for their own work, but the variability from instrument to instrument is too high to do this successfully without some other portable standard, such as a bead. The actual instrument values set are "real" electronically, but may not have much meaning to a researcher. There is too much detail to include here - I would recommend reading one of the many good books on flow cytometry that describe the instrumentation. Briefly, the threshold levels may be a percent of full scale, a channel number, or turns on a knob. PMT voltages determine the amplification of the photomultiplier tube that is converting photons to electrons, which is proportional to the voltage raised to some power, and varies from PMT to PMT. The gain describes what kind of electronic amplification is following the PMT, either linear with a certain gain factor, or logarithmic. Thus, your example of "FL1 640V gain1" say that measurment channel is in linear gain 1 with its PMT set to 640V. Marty Bigos Gladstone Flow Core >Dear flowers, > >there is some confusion here about how to document the electronic settings. >Can I write "the threshold was set to 20V"?, or better "the threshold >voltage was 20"??, i.e. are the voltage numbers of the PMTs really arbitrary >and not the real VOLT units? Once in a while I read things like "FL1 640V, >Gain1" etc. Is this wrong? > >Thanks, > >marcus >___________________________________________________________ >Marcus Reckermann >Forschungs- und Technologiezentrum Westküste der Universität Kiel (FTZ) >(Research and Technology Centre Westcoast of Kiel University) >Hafentoern >D-25761 Buesum >Tel. +49 (0)4834-604-204 or -261 >Fax. +49 (0)4834-604-299 >E-Mail: recker@ftz-west.uni-kiel.de >FTZ Web Site: www.uni-kiel.de/ftzwest/ >FTZ Flow Cytometry: www.uni-kiel.de/ftzwest/flow/flowhome.htm >________________________________________________ >Keep your computer busy with www.setiathome.ssl.berkeley.edu
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