I just wrote a bid request for an upgrade, and spent a LOT of time
writing specifications (not even really finished yet!). What Jeff
is attempting to do I believe could save much of the time I and
I'm certain others are expending in writing installation specs, and
will also help the purchasers and vendors better optimize
installations; I just want to make certain the instrument is
working correctly, and do not want to have vendor personnel at my
site any longer than necessary.
I ended up writing three sections of specifications, which I list
below in the hopes of generating more discussion on this topic. It
is important to note that the automated tests can be run fairly
quickly (certainly during an overnight), so these should not impact
the vendors much (assuming everything is working right :).
Some of the other tests really are difficult to specify for an
upgraded system (e.g., water suppression linewidth). Some others
I never figured out how to write, so I left them out: e.g., I felt
a test of "baseline flatness" would be very valuable. But
background signals (another test I couldn't figure out how to
write) and various pulse sequence/parameter settings would effect
this type of test. Moreover, I had trouble defining how to
measure "flatness." So nothing from me here (any ideas out there?).
The sample characteristics (e.g., standard probe specifications) and
parameter setup/choice (e.g., is 13 deg test as devised by Varian OK
or should Method IIIb of Morris' paper [JMR 78, 281-291 (1988)] be
used instead?) for each test are also important and worthy of
discussion.
Finally, I am curious if I left something important out, or whether
some tests are redundant and therefore wasting the vendor's time. I
will send the specifics of these tests as I wrote them up to Jeff,
and I hope many of you will send similar information. It would be
great to have a list to work from, perhaps including comments as to
what characteristics of the spectrometer each test is looking at.
1. Standard Probe Specifications - includes all the standard tests
(sens for 1H, 13C, 31P, 15N; line shape for 1H and 13C; and
pulse widths for 1H, 13C, 31P, 15N; all these separated for
various probe types--e.g. 31P sens only on a broadband probe).
2. Automated Test Procedures - running very much along the lines
of the Spectroscopy papers written by Vaughn and Kuhns at Florida
State. I view these tests as very important because they test a
variety of specific hardware features in an automated fashion that
can be repeated for regular checks and troubleshooting. The tests
I specified are the following:
RF Homogeneity (810/90)
Cancellation
Quad Image Rejection
Small-angle phase (accuracy of small phase adjustments)
30 deg pulse stability (amplitude stability)
pulse turnon (rise time)
pulse ideality (tests rectangularity of pulse shape)
glitch (noise/glitches with wide sweep width)
phase stability (13 deg test)
rf amplitude predictability (tests linearity)
rf excitation predictability (tests pulse shaping)
shaped rf amplitude stability
gradient profile (gradient calibration and linearity)
gradient recovery stability (similar to 30 deg test with grad)
gradient recovery (tests time for gradient recovery)
gradient echo (tests quality of bipolar grad echo)
gradient effect on cancellation (cancellation test with grad)
3. Department Specific Tests - these were tests that I included that
could not be included in an automated procedure:
amplifier droop (requires high speed scope)
salt tolerance (sucrose in D2O with/without NaCl)
water suppression linewidth (sucrose sample)
variable temp test (tuning stability, temp stability, and
temp gradients)
channel isolation (decoupler isolation from lock)
vibration and electrical noise (no vib or 60Hz, etc., in spectra)
shim stability and drift (line shape stability and magnet drift)
digital filtering
receiver noise figures
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Charlie Fry Tel: (608)262-3182
Director, MR Facility Fax: (608)262-0381
Chem. Dept., Univ. Wisconsin
Madison, WI 53706 USA email: fry@chem.wisc.edu
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