Philips Semiconductors
Magnetoresistive sensors for
magnetic field measurement
General
150
VO (mV)
100
50
0
MLC132
Hx = 4 kA/m
2 kA/m
1 kA/m
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2 | 4 | 6 | 8 | 10 | 12 | ||||||||
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Fig.23 Sensor output ‘Vo’ as a function of the transverse field Hy.
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 (Hd) and with an Hx of 3 kA/m or 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 Hx, the sensor will flip. This effect is reversible, with the sensor returning to the normal operating mode if Hd again becomes negligible (see Fig 24). However the higher Hx, 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 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
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handbook, halfpage |
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Hd |
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| SOAR |
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Fig.24 SOAR of a KMZ10B sensor as a function of auxiliary field ‘Hx’ (MLC133).
2000 Sep 06 | 20 |