>From: "Gregor Rothe" <gregor.rothe@klinik.uni-regensburg.de> >To: Cytometry Mailing List <cytometry@flowcyt.cyto.purdue.edu> >Date: Thu, 29 Jan 1998 08:38:55 +0100 >Subject: Re: 7-AAD,FITC and PE > > >Hello to all, > >It may be that this is a trivial question: >What is the effect of combining log and lin amplification, e.g. for >FITC and 7-AAD, on hardware compensation on instruments >using analog log amplifiers? My guess is that the setup probably >only has been designed and validated for log to log compensation. >Probably someone can comment on where the compensation is >actually performed on such instruments (before or after log >amplification)? > >Gregor Rothe > > > >*********************************************************** >Institute for Clinical Chemistry and Laboratory Medicine >University of Regensburg >D-93042 Regensburg, Germany > >Tel. +49 (941) 944-6204 >Fax +49 (941) 944-6202 > >E-mail: Gregor.Rothe@KLINIK.UNI-REGENSBURG.DE >*********************************************************** Hi Gregor, In the BD FACStar+ machine, the signal acquisition is as follows: [Optical Bench]PMT---->Remote Pre-amp---->[Electronics Console]---->FLUORESCENCE COMPENSATION---->Detector Height Measurement(switchable)---->LINEAR GAIN or LOG GAIN--->Pulse Display and Signal Level Processing with Threshold Detection---->A/D Conversion---->Dot Display and Computer. Because compensation is performed first, you are reducing the output of the signal before any LOG or LINEAR Gain. There is no 'optimised usage' and you can use the compensation in mixed amp mode (LIN and LOG). For example in Cell cycle work when PI(LIN) and BRDU(FITC)(LOG) are used it is often necessary to remove unwanted signal spillover from each parameter so you use compensation. I think most of the BD machines behave like this. Perhaps our more learned colleges could throw more light on the matter. Hope this helps. Andy... Andy Riddell PNAC MRC-LMB Hills Road Cambridge UK tel (0) 1223 402218 fax (0) 1223 412178 email ar3@mrc-lmb.cam.ac.uk Andy Riddell PNAC MRC-LMB Hills Road Cambridge UK tel (0) 1223 402218 fax (0) 1223 412178 email ar3@mrc-lmb.cam.ac.uk
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