It seems to me that if there is no internationally accepted definition
of signal to noise ratio in powder diffraction, then let me suggest that
this forum might be a way to define it once and for all. How about this?
SNR = (P-B)/SQRT(B).
Of course this would only give a value for a single peak. I suppose one
could also define a global SNR as a sum over all
Global SNR = sum over peaks (P-B)/SQRT(B).
Does this make sense?
Mike
-----Original Message-----
From: Van der Lee [mailto:[EMAIL PROTECTED]
Sent: 19 February 2008 09:09
To: rietveld_l@ill.fr
Subject: Re: advice on new powder diffractometer
Michael Glazer wrote the following on 19/02/2008 09:42:
>
> Or else one could take the peak intensity divided by the square root
of the background: this at least would improve with measurement time.
>
> For instance suppose we have a peak above background of 10000 counts
and a background of 1000 counts, this would give a signal to noise ratio
of roughly 322. If we measure ten times longer, the peak intensity
becomes 100000 and the background becomes 10000, giving a signal to
noise ratio of 1000, an improvement!
> So my question remains: what is the definition of signal to noise
ratio that is accepted for powder diffraction?
>
>
This at least coincides with data collection practice in single crystal
diffraction: there it is said that in order to improve the 'signal to
noise' ratio with a factor of two you have to count 4 times longer, or,
alternatively, double the generator power.
Arie
