Elekta Neuromag NM21283A, User Manual

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6 Principles of SQUID operation
32 NM21283A-A
The offset should be set so that the current vs. flux characteristics curve
crosses zero in order to be able to operate the flux-locked loop. The actual
point of operation to which the system locks is determined by the point
where the curve crosses zero line. The noise of the SQUID depends in
general on the value of the input flux. It has been found experimentally,
that for Vectorview SQUIDs the minimum noise is most often achieved
for an offset setting where the zero level crosses the current vs. flux char-
acteristics one-quarter above the minimum of the curve.
The gate voltage setting affects the amount of amplifier noise cancella-
tion. It is set to a value where the noise is at minimum.