Method and system for adjusting the sensitivity of a magnetoresistive sensor
View Patent ↗The system for measuring high currents or magnetic fields using a magnetoresistive sensor ( 80 ) includes a device for applying a known predetermined magnetic bias field H bias in a direction such that it has a non-zero component of the field perpendicular to a detection direction of the magnetoresistive sensor ( 80 ) that also corresponds to a direction of anisotropy of a layer of the magnetoresistive sensor, a device for measuring the variation in resistance of the magnetoresistive sensor ( 80 ) and means for determining the external magnetic field H to be measured from the measured resistance variation, the resistance of the sensor being subjected to a monotonic variation function.
1. A method of adjusting the sensitivity of a device including a magneto-resistive sensor and increasing the range of response of that device to an external magnetic field, characterized in that it consists in applying a known predetermined magnetic bias field H bias that is not homogeneous and is subject to known variations between a minimum value H biasmin and a maximum value H biasmax in a direction such that it has a non-zero component of the field perpendicular to a detection direction of said magnetoresistive sensor that also corresponds to a direction of anisotropy of a layer of the magnetoresistive sensor, so that the magnetic field to be measured can be determined by a monotonic function from the resistance variation of said magneto-resistive sensor,
wherein the bias magnetic field is caused to vary linearly between the minimum value H biasmin and the maximum value H biasmax , and
wherein the resistance R of said magnetoresistive sensor is given by the following equation:
R
=
R
0
+
R
1
(
H
bias
ma
x
-
H
bias
m
i
n
)
∫
H
bias
m
i
n
H
bias
ma
x
H
H
2
+
u
2
ⅆ
u
where:
R 0 is the resistance of the magnetoresistive sensor in the absence of an external field;
R 1 is the component of the resistance of the magnetoresistive sensor that is affected by the presence of an external magnetic field;
H is the external magnetic field to be measured; and
u is the variable varying from the minimum value H biasmin to the maximum value H biasmax of the bias magnetic field H bias .
2. A method according to claim 1 , for adjusting the sensitivity of a device including an anisotropic magnetoresistance sensor, characterized in that the known predetermined bias magnetic field H bias is applied in a direction such that it has a non-zero field component in a direction perpendicular to the direction of flow of the current in said sensor.
3. A method according to claim 1 , for adjusting the sensitivity of a device including a giant magnetoresistance sensor or a tunnel magnetoresistance sensor including a hard ferromagnetic layer trapped in a reference direction, characterized in that the known predetermined bias magnetic field H bias is applied in a direction such that it has a non-zero field component in a direction perpendicular to said reference direction of the hard ferromagnetic layer.