Dr. Shlomchik,
It sounds like the problem may be a fluidic/pneumatic one.The nominal
time delay on the FacsCaliber is 22us, with the calibration circuit having a
range of +/- 2us. If your cells are reaching the 488nm laser in less than
20us or greater than 24us after they pass the 635nm laser you will get a
"signal out of range error".
At 4.5 PSI (sheath Tank pressure) cell velocity is 6 um/us. With a
nominal time delay of 22us, the nominal distance between the two lasers is
132um. If you divide 132um by the upper and lower limits of the
calibration window (24us and 20us) you see that the cell velocity need only
vary outside the range of 5.5 - 6.6um/us to fall out time delay calibration
window.
This change will most likely be caused by a variation in sheath tank
pressure or a restriction in sheath flow. If your sheath tank pressure
varies a few tenths of one PSI from the rated pressure of 4.5 PSI it can put
you out of the time delay calibration window. Even the level of fluid in
your sheath tank can change the velocity of your cells moving through the
laser. Eric Chase of Cytek Development wrote an informative paper on this
very subject. I would be happy to fax a copy to anyone who is interested.
Best Regards,
Raymond Lannigan
Tritech Inc.
2014 Renard Ct. Suite I
Annapolis, MD 21401
1-410-266-1522
1-800-886-7004
www.tritechinc.com
-----Original Message-----
From: Warren D. Shlomchik <wds8@email.med.yale.edu>
To: cyto-inbox
Date: Tuesday, June 27, 2000 4:49 PM
Subject: problems with time delay calibration on FACS Calibur
>
>Dear Flowers (in particular FACS Calibur users),
>
>We have a new FACS Calibur and have had persistent problems with
>reproducibly being able to set time delay calibration. In
>particular, we get the error message, "signal out of range...unable
>to set time delay." BD has replaced an EPROM and a board, but the
>problem intermittently persists. In speaking to users of 3 other
>Caliburs I discovered that they too had seen this problem. I'd
>appreciate any comments from other two laser users on the Calibur and
>will summarize the responses to the list. Many thanks.
>
>
>Warren
>
>
>Warren D. Shlomchik, M.D.
>Assistant Professor of Medicine
>Yale University School of Medicine
>Section of Medical Oncology
>333 Cedar Street WWW217
>New Haven, CT 06520
>
>phone:(203)737-2478
>FAX: (520)395-8571
>
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