Dear Kirk,
this is not a problem at all.
What you are observing is the underlying, and very slow, drift of the B0 field of your magnet.
If I remember my Z0 calibrations correctly, you are seeing about 5 Hz/week of 1H frequency drift, which is a few orders of magnitude less than the commonly guaranteed drift for 400 MHz magnets (4Hz/hr, or even higher), but not entirely unheard of.
Looks like you have an excellent magnet!
- Knut
> On Aug 26, 2015, at 2:42 PM, Kirk Manfredi <kirk.manfredi_at_uni.edu> wrote:
>
> We have a 2004 Inova 400 with a shielded 54 mm Oxford magnet. Last May we had an Agilent OneProbe installed and have been very happy with its performance. At the time of installation I logged the value of Z0 (on resonance) on a standard sample that we keep int the magnet when it is not in use (+1048). Since June of 2014 the Z0 value continually decreases. I is now at -192. It seems to change about 15 units a week. There are no other symptoms to the system (Unless I ran a long acquisition overnight?). I contacted Agilent about this problem some 6 months ago and they gave me the procedure to reset the spectrometer frequency but told me not to do it until there is a degradation in spectrometer performance.
>
> Any suggestions as to what this problem maybe and where it will lead?
>
> Kirk Manfredi
> University of Northern Iowa
Received on Thu Aug 27 2015 - 10:26:39 MST