Elekta Neuromag NM21283A, User Manual

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Tuning procedures 9
NM21283A-A 51
C H A P T E R 9
Tuning procedures
The tuning program is capable to perform several automatic tuning opera-
tions in addition to manual tuning. This chapter describes the tuning oper-
ations available.
All the tuning operations are based on the measurements described in the
previous chapter. They typically employ a loop containing a measurement
and adjusting of some parameters.
The tuning procedures available are the following:
Tune
Optimize the white noise level by adjusting bias, offset, and gate
settings.
Tune (fine)
Same as “Tune”, but with smaller steps in adjustments.
Tune (gate)
Same as “Tune”, but only the gate value is adjusted.
Tune (offs)
Adjusts the offset setting so that the zero line in the plot crosses
the curve at specified level.
9.1 Noise level based tuning
To optimize the noise level of the sensors, Tuner provides procedures to
automatically tune the operating point parameters. All three routines are
similar. They differ only on adjusted parameters and the size of the adjust-
ment steps.
The basic job “Tune” is provided for general purpose everyday tuning. A
detailed description of its usage is given in part “Basic Usage” starting on
page 3. It measures the white noise level, adjusts one parameter, and then
measures again. If the new noise level was lower than the previous, the
new settings are accepted. The sequence of adjustment is such that the
gate value is optimized first starting with rather large steps that then
shorten quite quickly. After the initial rounds on gate, the routine enters
into a loop optimizing sequentially bias, offset and gate values with a step
size of 2.
The “Tune(fine)” works similarly optimizing all parameters using step of
one unit.
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