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Dear Nathalia,

I would guess that 95% of the time, z-drift is caused by temperature
instability in your room, incubator or both, rather than a mechanical
fault with your microscope. This has been discussed many times
previously on this list. You should search the archives for "z-drift" or
"Focus Drift". Objective lenses are made of brass which will expand and
contract with very slight changes of temperature. It is not a trivial
matter to control the temperature of the room and incubator accurately
enough to be able to perform time lapse microscopy. I have just spent
two weeks playing with the air-conditioning system and incubator to
achieve stability after the hospital switch from winter heating to
summer cooling.

To gain more understanding of your problem while you are waiting for a
service call I suggest you look at the tutorial I have placed online at:

www.ludwig.edu.au/confocal/drift 

If you follow this procedure you should be able to work out if the
movement of the lens is always in:
-A downward direction - Gravity causing drift may be the cause

-An upward direction - Your lens is still warming up to the incubator
temperature

- Oscillating up and down 
	- temperature instability caused by heating or cooling 
	system in the room. 
	-Or a microscope incubator system with either an on/off 
	controller (get a controller with "fuzzy logic" or "PID
control")
	-PID controller requires "Tuning" (read the manual).

Temperature control is not trivial, you need to invest quite a bit of
time to get it right.

Cheers


Stephen H. Cody
Microscopy Manager
Central Resource for Advanced Microscopy
Ludwig Institute for Cancer Research
PO Box 2008 Royal Melbourne Hospital
Victoria,      3050
Australia
Tel: 61 3 9341 3155    Fax: 61 3 9341 3104
email: [log in to unmask] 
www.ludwig.edu.au/labs/confocal.html
www.ludwig.edu.au/confocal

Tip: Learn how to receive reminders about you microscope booking: 
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-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On
Behalf Of Nathalia Holtzman
Sent: Friday, 9 November 2007 12:59 AM
To: [log in to unmask]
Subject: Z-drift

Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

Hi all, 
I need some help. We have a 1 year old Leica SP5 inverted scope and
pretty
much all of a sudden we started to get z-drift. Every time you do a time
lapse, no matter what the z-step or time interval, the system does not
start
at the top of the sample, it moves down significantly and progressively.
Anything I can do to fix this?

I have called the service rep but would like to fix the problem ASAP. It
is
possible that I am the first person to use the system for this
application
since we upgraded the software and firmware.

Nathalia

-- 
Nathalia Glickman Holtzman Ph.D.
Department of Biology SB D328
Queens College, CUNY
65-30 Kissena Boulevard
Flushing, NY 11367

Office: 718-997-3678
Lab: 718-997-3517
Fax: 718-997-3445


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