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2000 Sep 06 7
Philips Semiconductors
Magnetoresistive sensors for
magnetic field measurement
General
Figure 7 also shows that the flipping itself is not
instantaneous, because not all the permalloy strips flip at
the same rate. In addition, it illustrates the hysteresis effect
exhibited by the sensor. For more information on sensor
flipping, see Appendix 2 of this chapter.
Effect of temperature on behaviour
Figure 8 shows that the bridge resistance increases
linearly with temperature, due to the bridge resistors’
temperature dependency (i.e. the permalloy) for a typical
KMZ10B sensor. The data sheets show also the spread in
this variation due to manufacturing tolerances and this
should be taken into account when incorporating the
sensors into practical circuits.
In addition to the bridge resistance, the sensitivity also
varies with temperature. This can be seen from Fig.9,
which plots output voltage against transverse field ‘H
y
’ for
various temperatures. Figure 9 shows that sensitivity falls
with increasing temperature (actual values for given for
every sensor in the datasheets). The reason for this is
rather complex and is related to the energy-band structure
of the permalloy strips.
Fig.8 Bridge resistance of a KMZ10B sensor as
a function of ambient temperature.
handbook, halfpage
40 160
3
1
MBB897
2
0 40 80 120
T ( C)
o
amb
bridge
R
(kΩ)