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Z31980_00_03
Installation
6.6.1 Setting the spectrometer frequency
The next screen asks for the configuration name and spectrometer frequency (1H) in
MHz. It is usual for Avance300 systems to set it to 300.13MHz. The field of the magnet is
close to the corresponding value and the correct field value is achieved by adding a B
0
shim current to it. The Fourier console works the same way. But in order to keep the B
0
shim current at a low value, the frequency should be set to a value close to the one
which originates from the actual field of the respective magnet.
At this point, there is a minor inconsistency which can’t be solved. The value of the mag-
netic field is checked using the NMR console to detect a proton or Deuterium resonance
line. That means that it is necessary to run cf twice. The first run can be done with the
default 1H frequency of 300.13MHz. Without using the lock, one has to search for the 1H
spectrum of a suitable sample (Sucrose or Doped Water, use zg with a pulse length of
about 5us and a spectrum width of >200kHz). The frequency at which the spectrum is
detected, is close enough to the correct value. Choose a rounded value next to it and re-
run cf with this value.
In the example shown here, the magnet’s field resulted it a proton frequency of roughly
300.178MHz. This could be rounded up to 300.18 or down to 300.17, e.g., to have num-
bers being easy to memorize.
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