The minispec Menu Functions
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If the Save button stays disabled on a connected minispec, customize your minispec
software to provide access to the calibrated application.
Experiment parameters that can be edited through the Acquisition Parameters menu:
Figure8.9: The Acquisition Parameter Table
Scans (1 – 32000)
Scans is used to set the number of times the NMR experiment should be repeated for signal
averaging before the result is evaluated. The required number of scans depends on the
signal strength, the desired signal-to-noise (which will limit the precision of the
measurement), and the desired speed of analysis (time between scans is set by the Recycle
Delay). Signal to noise improves with the square root of the number of scans. The remaining
number of scans during an experiment is shown in the lower right corner of the display.
RD (seconds)
RD, or Recycle Delay, is used to set the time delay in seconds between repeated scans. The
recycle delay is usually set just a little longer than the relaxation time of the sample. If the
delay is deliberately made shorter than the sample relaxation time, one or more dummy shots
can be made prior to the experiments in order to ensure that the first scan has the same
history as all subsequent scans.
Gain (mq-Series NF systems: 40 – 119dB)
Gain sets the signal amplification in the receiver. It is a common procedure to set the gain
such that the highest part of the signal reaches about 80% of the signal input range. It is
known that the noise start to increase significantly when exceeding 95…100dB. As the NF
minispec features a high signal resolution like 14/15 bit, it is also possible to work with lower
input signal levels, thus avoiding gain values that are too high.
Note that the gain should not be changed for calibrated applications. If the range of input
signals is too large for one gain setting, it may be better to have several calibrations with
different gain settings.
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