Date: Thu, 29 Jun 2023 08:58:45 -0600
Ken,
I've had this problem with my DDR 500 MHz relatively recently. While
it's still possible to fiddle with the potentiometer on the upper barrel
itself (this was the only way to adjust the sample detection sensitivity on
the Inovas), it's much more convenient with the DDR-era consoles to fiddle
with the potentiometer on the "magnet leg" (i.e., the pneumatics box).
There's a small black knob labeled "sample sensor" that's on the same side
as the power switch and various control cables (at least on the DDR
version, see attached image).
Not only does this knob give you the convenience of not removing the
upper barrel, you have some interplay with the main magnetic field itself
and the sensor in the upper barrel, so adjusting the potentiometer on the
upper barrel with it out of the magnet gives a different response than when
it's in the magnet, resulting in lots of in/out cycles to get that
potentiometer where you want it.
-Scott
[image: image.png]
On Thu, Jun 29, 2023 at 8:45 AM Kenneth Sharp-Knott <kknott_at_vt.edu> wrote:
> I have an Agilent era MR400DD2 with a OneNMR probe. Recently it is failing
> to detect many spinners when they are introduced to the magnet (providing
> the counter intuitive 'sample detected in upper barrel error'). I don't
> think it's a rotation air issue. I do remember adjusting a couple
> potentiometers way back in the day when we first received this instrument.
> Before I try that, any troubleshooting tips you can recommend?
>
>
>
--
Dr. Scott Burt
Professor
NMR Facility Manager
Department of Chemistry and Biochemistry
Brigham Young University
C414 BNSN / C008A BNSN
Provo, Utah 84602-5700
Phone: (801) 422-2404
Fax: (801) 422-0153
chembio.byu.edu/nmr-facility/
email: scott_burt_at_byu.edu
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