[FDS] new intensity results

[Borries Demeler]

Hi Jack,

thanks for the information - that sounds like a good series of
experiments to try! Virgil and I are both out of town right now,
but we will definitely try it out and report back on what we find.

I am not sure what you mean with increasing the number of laser flashes,
isn't the laser a continuous light source? Maybe it's just the number of
readings. I also noticed a correlation between noise and speed. The higher
the speed, the higher the noise level. Is this related to the number of
averages? When you run faster, you can't collect as many averages?

It may be true that like in the UV-absorbance optics the more you average
the fewer scans you can collect. Then the question comes down to what are
better statistics: more by noisier scans, or fewer, but better quality data.

Anyway, I'll report what we find. Thanks again for this tip!

-Borries


> Bo
>
> Sorry I was out of town or I would have responded earlier.  Here is my
> two cents!
>
> The best way to test the signal / noise characteristics of FDS is to do
> the variations yourself.  Only two experimental things will improve the
> signal/noise, 1) increase the gain, 2) increase the # of laser flashes
> you average.  Not sure where Tom gets the 1% from but its not true at
> all gains and for all signal intensities.  My suggestion is to rerun
> that sample and collect data multiple ways at the same time - the
> software lets you do that.  Collect data at 55%, 65%, 75%, 85%, etc up
> to the point where it tops out at 4096 counts.  I predict that 2000
> count data will have much better signal/noise than 200 count data.  Then
> choose a gain and collect data with variable averages, say 1, 4, 9 , 16
> , 25 and the signal/noise will improve by 2, 3, 4, 5-fold up to the
> noise limits of the instrument.  Yes, focusing and other optical
> features will help, but ultimately its just a PMT counting photons,
> isn't it!
>
> -------------------------------------------------------------------
>  Dr. John J. "Jack" Correia
>  Department of Biochemistry
>  University of Mississippi Medical Center
>  2500 North State Street
>  Jackson, MS  39216
>  (601) 984-1522
>  fax (601) 984-1501
>  email address: jcorreia at biochem.umsmed.edu
>  homepage location: http://biochemistry.umc.edu/correia.html
>  dept homepage location:    http://biochemistry.umc.edu/
> -------------------------------------------------------------------
>
>
>
>


-- 
Borries Demeler, Ph.D.
The University of Texas Health Science Center at San Antonio
Dept. of Biochemistry, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900
Voice: 210-567-6592, Fax: 210-567-4575, Email: demeler at biochem.uthscsa.edu