Some years ago, when we started doing PFG diffusion measurements in a big
way, I retrofitted our then AM console with a lock hold unit built by Rolf
Tschudin, intended to prevent "lock pull." When triggered ahead of a PFG
pulse, it did a sample & hold on the lock level and continued to feed that
level through the circuitry for a user-selectable interval while the lock
recovered. Rolf's modad seemed to work extremely well and we used it
until we reconsoled the AM system earlier this year.
The Bruker Avance consoles have a similar feature built on, or at the very
least, display a somewhat annoying and impossible-to-get-rid-of 'LOCK HOLD
ACTIVATED' message on the BSMS panel during gradient experiments.
Concerning the recent posts about distortion with pfg water suppression:
while an optimal lock phase would seem to have no down side, some people
report that lock phase adjustment minimizes, but does not necessarily
remove, the distortion. As a relatively inexperienced new user of an
Inova system, I am curious to know: do these consoles have a lock sample
& hold? If so, is there a software or hardware configuration needed to
adjust/optimize the time it is activated? (On Rolf's unit, this was
accomplished with a front panel knob. Gee, I miss knobs.)
Just curious, Dave Vander Velde, University of Kansas
Received on Thu Sep 07 2000 - 13:13:51 MST