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Philips Semiconductors
Magnetoresistive sensors for
magnetic field measurement
handbook, full pagewidth
A Safe Operating ARea (SOAR) can be determined for
magnetoresistive sensors, within which the sensor will not
flip, depending on a number of factors. The higher the
auxiliary field, the more tolerant the sensor becomes to
external disturbing fields (H
greater, the sensor is stabilized for all disturbing fields as
long as it does not irreversibly demagnetize the sensor. If
Hd is negative and much larger than the stabilising field H
the sensor will flip. This effect is reversible, with the sensor
returning to the normal operating mode if H
becomes negligible (see Fig 24). However the higher H
the greater the reduction in sensor sensitivity and so it is
generally recommended to have a minimum auxiliary field
that ensures stable operation, generally around 1 kA/m.
The SOAR can also be extended for low values of H
long as the transverse field is less than 1 kA/m. It is also
recommended to apply a large positive auxiliary field
before first using the sensor, which erases any residual
hysteresis
2000 Sep 06
150
V
O
(mV)
100
50
0
2
Fig.23 Sensor output 'V
) and with an H
of 3 kA/m or
d
x
again
d
0
4
6
8
' as a function of the transverse field H
o
12
handbook, halfpage
H d
(kA/m)
,
x
8
,
x
4
as
x
II
0
0
Fig.24 SOAR of a KMZ10B sensor as a function of
auxiliary field 'H
20
MLC132
H =
x
4 kA/m
2 kA/m
1 kA/m
10
12
H (kA/m)
y
.
y
SOAR
I
1
2
' (MLC133).
x
General
MLC133
3
4
H (kA/m)
x
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