Magnetic Sensor Device With Field Compensation
The invention relates to a magnetic sensor device ( 10 ) comprising an excitation wire ( 11 ) for the generation of a first magnetic field (B 1 ), a GMR sensor ( 12 ) for sensing stray fields (B′) generated by magnetized beads ( 2 ), and a compensation wire ( 13 ) for the generation of a second magnetic field (B 2 ) that compensates the first magnetic field (B 1 ) in the GMR sensor ( 12 ). Preferably, the excitation and compensation wires ( 11, 13 ) are disposed symmetrically above and below the GMR sensor ( 12 ) and supplied with parallel currents (I 1 , I 2 ) of equal magnitude. In a second mode of operation, the magnetic fields (B 1 , B 2 ) can be set such that the substantially compensate in the region containing the beads ( 2 ), allowing to calibrate the GMR sensor ( 12 ).
1 . A magnetic sensor device ( 10 , 110 ), comprising
a) at least one magnetic field generator ( 11 , 111 a, 111 b ) for generating a first magnetic field (B 1 ) in an investigation region;
b) at least one associated magnetic sensor element ( 12 , 112 ) having a sensitive direction (D);
c) at least one magnetic field compensator ( 13 , 113 a, 113 b ) for generating a second magnetic field (B 2 );
d) a controller ( 15 , 115 ) coupled to the magnetic field generator ( 11 , 111 a, 111 b ) and the magnetic field compensator ( 13 , 113 a, 113 b ) for controlling the generation of the first and the second magnetic field (B 1 , B 2 );
wherein the magnetic sensor device ( 10 , 110 ) is designed in such a way that it allows an operation mode in which the first and second magnetic fields (B 1 , B 2 ) substantially compensate in the magnetic sensor element ( 12 , 112 ) with respect to the sensitive direction (D) thereof.
2 . The magnetic sensor device ( 10 , 110 ) according to claim 1 , characterized in that the magnetic field generator ( 11 , 111 a, 111 b ) and the magnetic field compensator ( 13 , 113 a, 113 b ) are arranged symmetrically with respect to the sensitive direction (D) of the magnetic sensor element ( 12 , 112 ).
3 . The magnetic sensor device ( 10 , 110 ) according to claim 1 ,
characterized in that the magnetic field generator ( 11 , 111 a, 111 b ) and/or the magnetic field compensator ( 13 , 113 a, 113 b ) comprise conductor wires.
4 . The magnetic sensor device according to claim 1 ,
characterized in that the magnetic sensor element ( 12 , 112 ) is a magneto-resistive element, preferably a Giant Magnetic Resistance, or Tunnel Magneto Resistance or Anisotropic Magneto Resistance, and/or a Hall sensor.
5 . The magnetic sensor device ( 10 , 110 ) according to claim 1 ,
characterized in that the magnetic sensor element ( 12 , 112 ) is disposed in the middle between a number of magnetic field generators ( 11 , 111 a, 111 b ) and the same number of magnetic field compensators ( 13 , 113 a, 113 b ), wherein the configuration of the magnetic field generators ( 11 , 111 a, 111 b ) is the same as the configuration of the magnetic field compensators ( 13 , 113 a, 113 b ).
6 . The magnetic sensor device ( 10 , 110 ) according to claim 1 ,
characterized in that it is realized as an integrated circuit.
7 . The magnetic sensor device ( 10 , 110 ) according to claim 1 ,
characterized in that the controller ( 15 , 115 ) is adapted to control the first and the second magnetic field (B 1 , B 2 ) in a second operation mode such that they substantially compensate in the investigation region.
8 . The magnetic sensor device ( 10 , 110 ) according to claim 7 ,
characterized in that the controller ( 15 , 115 ) is adapted to calibrate the magnetic sensor element ( 12 , 112 ) based on the second operation mode.
9 . The magnetic sensor device ( 10 , 110 ) according to claim 1 ,
characterized in that it comprises an energy supply which feeds both the magnetic field generator ( 11 , 111 a, 111 b ) and the magnetic field compensator ( 13 , 113 a, 113 b ).
10 . A method for the detection of at least one magnetic particle ( 2 ) in an investigation region, the method comprising the following steps:
a) generating a first magnetic field (B 1 ) in the investigation region;
b) generating a second magnetic field (B 2 ) such that it substantially compensates the first magnetic field (B 1 ) in the sensitive direction (D) of magnetic sensor element ( 12 , 112 );
c) sensing a magnetic property of the particle ( 2 ) with the magnetic sensor element ( 12 , 112 ).
11 . The method according to claim 10 ,
characterized in that the first and the second magnetic fields (B 1 , B 2 ) are generated by parallel currents (I 1 , I 2 ) of equal magnitude.
12 . The method according to claim 10 , characterized in that it further comprises the following step:
d) changing the magnetic fields (B 1 , B 2 ) such that they substantially compensate in the investigation region, and calibrating the magnetic sensor element ( 12 , 112 ) based on such a condition.
13 . Use of the magnetic sensor device ( 10 ) according to claim 1 for molecular diagnostics, biological sample analysis, or chemical sample analysis.