Basic Information on ProTune

(Dec. 2009)

You can find information on ProTune usage in

NMR Spectroscopy User Guide, 01-999343-00 rev. B 1207, (see Chapter 2.5, p. 31)

Also, information on ProTune setup, calibration and other administrative issues could be found
on pages 60 and 86 (chapters 5.2 and 8.2) of this manual
VnmrJ 2.2C Installation and Administration,  01-999341-00 rev. E 0508

(Very similar docs are in the appropriate manuals for VJ2.3A and VJ2.2D – similar chapters)

 

If for some reason you can't find hard copies of these manuals, please download them from our external web site:
  http://www.varianinc.com/products/nmr/apps/

  and click on Publications
User - usergroup
PW  -  vnmrj4me

 

 

1. About Sweep range calibrations:
     We need to calibrate the System's RF Path performance without the probe – to figure out all cables/amps/preamp, etc impurities and local resonances, so when actually looking at the tuning dip we’d subtract the effects of the circuitry before the probe.
   Also, after calibration we are able to quantify how well the probe is tuned in dB:
   from the full rejection at the level “1” to theoretical full absorption by the perfectly tuned probe at the “0”-level shown in the ProTune plots.This RF Reflection Calibration data (or Sweep Range Calibrations) is stored in
   /vnmr/tune/tunecal_ProbeName
   and it has nothing to do with p-files (or ProTune persistence files) - see below.
   You need to recalibrate if any part of the RF path has been replaced (1/4-wave cable, other cables, amps, preamps, etc.).
   Also, UNFORTUNATELY, you must recalibrate Sweep Range after every the VNMRS or MR-400 system reboot - otherwise the calibration data will be applied with a wrong phase and autotuning may fail (more likely)… This will be fixed in VJ3.0.
   
   
2. About the p-files:
       These files describe specific probe tuning features – they are probe-related, so we copy generic (or probe-special) files into the /vnmr/tune/ProbeName directory.
   As soon as an autotuning is requested by the logged in user, all motor#... and chan#0 files will be copied locally to the  user’s directory …UserName/vnmrsys/tune/ProbeName (created automatically). Other chan# files will be copied to the local directory when corresponding frequency range is requested for auto tuning to other nuclei.
    When tuning is successful local chan#... files are being updated with the data obtained by the ProTune software during the auto tuning process – Tune and Match sensitivities, motors’ position, etc. and a new Ref-lines might be recorded.
   Sometimes after attempting to tune on a difficult (salty, lossy, etc.) sample, or when Sweep calibrations are not adequate, the system may detect a false successful tuning and record a wrong Ref-line in the user’s local …vnmrsys/tune/ProbeName directory – then the next "normal" sample tuning might fail.
   That’s why it is advisable to remove local p-files sometimes, as needed.
   
   
3. About the Tuning Quality Criteria:
      Three tuning quality criteria in VJ 2.x are Coarse, Medium, Fine. The auto tuning process will stop when the tuning dip at the target frequency is below
   -10dB for Coarse,
   -14dB for Medium and
   -18dB for Fine criterion.
   
       If a "difficult" (salty) sample is inserted in the probe, it might be impossible to achieve the Fine or even Medium criterion, and the ProTune software would just quit leaving the probe completely mistuned. So, it is recommended using the Coarse criterion in such cases.