2000 Sep 06 20
Philips Semiconductors
Magnetoresistive sensors for
magnetic field measurement General
Fig.23 Sensor output ‘Vo’ as a function of the transverse field Hy.
handbook, full pagewidth
MLC132
024681012
O
(mV)
H (kA/m)
y
H =
4 kA/m
x
2 kA/m
1 kA/m
0
V
100
150
50
A Safe Operating ARea (SOAR) can be determined for
magnetoresistivesensors, 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 (Hd) and with an Hxof 3 kA/m or
greater, the sensor is stabilized for all disturbing fields as
long as it does not irreversibly demagnetize the sensor. If
Hdis negative and much larger than the stabilising field Hx,
thesensor will flip. This effect is reversible, with the sensor
returning to the normal operating mode if Hd again
becomes negligible (see Fig24). However the higher Hx,
the greater the reduction in sensor sensitivity and so it is
generallyrecommended 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 Hx as
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
Fig.24 SOARof a KMZ10B sensor as a function of
auxiliary field ‘Hx’ (MLC133).
handbook, halfpage
012 4
12
0
4
8
MLC133
3
Hd
(kA/m)
H (kA/m)
x
I
II
SOAR