
14-6 Sensors and Sensor Technology
e need for shielding at lower frequencies down to dc has led to the use of high-permeability materi-
als (e.g., mu-metal) for shunting magnetic elds external to the experimental region. For biomagnetic
me
asurements,
it ma
y
be ne
cessary
to en
close
no
t
on
ly
th
e
se
nsing
de
vice
bu
t
al
so
th
e
su
bject
in an MS
R
with large interior dimensions (e.g., 4 m × 3 m × 2 m). e use of multiple shields can act to further
shield the interior of an MSR with commercial MSRs oering shielding factors >40 dB at dc, increasing
to 1
00+
d
B
a
bove
1
00
H
z
.
e eective use of magnetic shields can reduce the background magnetic noise to ...