Grafidy - Fixture check

When in Auto mode, a number of signal checks are performed to ensure the proper state of the Grafidy fixture.

1. The peak-to-peak deviation in initial magnitude signal as a function of FID is checked to verify that it is below a maximum value. This value is a measure of the relative value of the T1 (longitudinal spin relaxation time) of the sample and the TR used by the pulse sequence (time between consecutive RF pulses). A small value indicates that sufficient time was provided to allow the sample to relax.
2. The standard deviation of the field plot is checked to verify that it is below a maximum value. This value is related to the SNR of data. A small deviation indicates high SNR.
3. he location of each sample in the magnet bore is measured. A message is presented if any sample is more than 1.5 cm from its ideal location. When presented, you have three options:
   1. Abort to stop data acquisition so that the fixture can be repositioned in the bore.
   2. Continue and the next scan starts, but continue to check fixture position.
   3. Continue without further prompting, which allows the next scan to start and suppresses any further position error messages.

   Figure 1. Sample position error message