The present invention describes a method enabling one to shield a device
that measures weak biomagnetic signals from strong magnetic interference
fields. The measurement sensors are provided with a feedback compensation
loop, the difference signal of which is obtained from the measurement
sensors themselves. As the actuator of the feedback function, one or more
coils are responsible for eliminating, the external interference fields
in the region of the sensors. Difference signals can be generated as a
linear combination from the signals of two or more sensors. In the
control logic, the SSS method can be used to numerically separate the
biomagnetic signal being measured from the signals produced by the
sources--compensation coils and interference sources--disposed outside
the measurement region. The interference suppression can be enhanced by
placing the assembly of sensors and the actuators within a magnetically
shielding room.