[RASMB] Lamp intensity fluctuations

[Borries Demeler]

> 
> Hi, 
> I should have been a little bit more precise about my sample.
> I loaded a cell with water (dH20) in the reference channel and a sample of
> 0.5 Abs in the sample channel. I recorded intensities instead of OD values.
> Thereafter I plotted the lamp intensities from the reference channel (water)
> as a function of the scan number using Ultrascan. The same graph can be
> produced using Origin, plotting the raw intensities at any given radial
> position, or the average of it, as a function of the scan number. Basically
> the same profile. 
> Titus
> 

Titus,

the variation in lamp intensity on your water measurement over time is 
much greater than anything I have ever observed on any of our machines
or for that matter on any other machine, and I'm certain that this is not
normal. It would cause a continuous shifting of baseline throughout your
experiment. I would even suspect that this would cause problems if you were
to use it in absorbance mode, but there it would probably be somewhat reduced
since the reference value is always measured right after the sample measurement,
and hence the fluctuation would be a lot smaller between measurements.
Intensity variations of +/- 1-2 % over the course of the experiment are 
typical on our instruments.

I hope Tom can confirm that this is an unusual symptom and suggest which
component may be faulty.

-Borries