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Z31980_00_03
Installation
There is a problem with this approach which also applies to the BSMS. The lock sends a
series of RF pulses with a rate of 1kHz to the 2H coil. This results in an excitation profile
of a central peak and a number of additional peaks on a 1kHz grid. These slowly decay
in amplitude as their distance to the central peak increases.
Setting the sweep to a large amplitude clearly shows the problem.
There is more than one “resonance” due to the excitation grid and it is not obvious which
one is due to the central peak.
The rate of RF pulses on the BSMS is 6.66kHz. So, the effect is less obvious and the
determination of the right sweep signal is much easier.
Second Approach: The "flock" AU Program
There is an alternate way of finding the correct lock field. Instead of using the lock
instruction, it is possible to start an AU program called flock. flock asks for the lock sol-
vent, creates a temporary 2H dataset and starts an acquisition to find the lock signal in
the 2H spectrum. It compares the ppm shift of the 2H signal to the default value from the
edlock table. The difference in ppm is then converted to a shift in the lock field. The new
lock field is displayed in a pop-up window. Additionally, flock informs the operator how
many solvent peaks have been found and if this number is in agreement with the num-
ber of resonance lines for the selected lock solvent. In case, the number of signals is dif-
ferent from the expected value, flock uses the peak with the highest intensity to calculate
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