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minispec.exe Software for Diagnostic and Service Purposes
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Experiment parameters that can be edited through the Acquisition Parameters menu:
Figure 8.11: 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 R ecycle D elay, 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 (dB)
Gain sets the signal amplification in the receiver. For best results, set the gain such that the
highest part of the signal reaches about 90% of the signal input range.
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 for
different gain settings.
Dummy Shots (0 - 32,000)
Pulses before the measurement can be made prior to the experiments (<Setup> <Program>
Menu), in order to ensure that the first scan gas the same history as all subsequent scans.