I really just wanted to open a bit of a discussion here.
Recently we have been doing some work on our 500's looking for very
small amounts of impurities in samples by running proton spectra.
Typically we use as much oversampling as we can and still some of the
impurities are near the limits of detection. I know there must be other
people out there interested in doing the same thing (particularly in
pharmaceuticals), so the question I want to raise is whether there is a
good reason why we should still be using 16-bit ADC's and oversampling
when 24-bit ADC's are now readily available? (A 24-bit/96 kHz stereo
soundcard for a PC costs $US500 or less, which doesn't seem much in the
context of a $US500k spectrometer). I think I'm right in saying that to
achieve the same accuracy/dynamic range using oversampling you need an
oversampling factor of 256, which is not realistic.
I realize that there are other aspects to DSP, but actually extending
the dynamic range at very little cost seems to me the kind of thing we
should be looking for in terms of development, particularly if you start
looking at things like cryo-probes at high field (I wish!). Is it
simply that the spectrometer manufacturers don't feel this is a
priority? Do you feel it's important, or is this really a minority
interest?
--
Alan.
Alan M Kenwright
Senior Research Officer (NMR)
Department of Chemistry
University of Durham
Durham DH1 3LE UK
Received on Thu Jul 25 2002 - 13:25:51 MST