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Michael Weber wrote:

> 
> Regarding the scan speed vs. averaging, I have the impression that
> averaging is the better way to go. With a constant light source as sample,
> reducing the scan speed results in a rather linear decrease of noise,
> whereas averaging gives exponential decrease. Based on these measurements,
> up to 8 times averaging is better than decreasing the speed to the similar
> period.
> 

This surprises me. How can averaging give an exponential decrease? I would 
expect the S/N to increase as the square root of the number of averages.

In addition, if one considers the sum of N scans, it will include the sum of N 
readouts (ie, N x readout noise). On the other hand, increasing dwell time x N 
will increase the signal by a factor of N, but will only subject the signal to a 
single readout. So I dont understand the above observation.

--aryeh
-- 
Aryeh Weiss
School of Engineering
Bar Ilan University
Ramat Gan 52900 Israel

Ph:  972-3-5317638
FAX: 972-3-7384050