MAGNETOMETER

• US 20110227569A1
• Filed: 03/19/2010
• Published: 09/22/2011
• Est. Priority Date: 03/19/2010
• Status: Active Grant

• Current Assignee: Memsic Semiconductor (Wuxi) Co., Ltd. (MZ Investment Holdings Ltd.)
• Original Assignee: Memsic Incorporated (MZ Investment Holdings Ltd.)
• Inventors: Liu, Haidong, Laich, Mark, Marcelino, Jerome S., Li, Zongya, Cai, Yongyao, Zhao, Yang
• Granted Patent: US 8,525,514 B2
• Time in Patent Office: Days
• US Class Current: 324/252
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G01R 33/096 anisotropic magnetoresistance sensors
• CPC Class Codes: G01R 33/18 Measuring magnetostrictive properties

Abstract

A magnetometer with only a SET operation for initiating a magnetic orientation within a magnetic field sensor based on anisotropic magnetoresistive (AMR) technology. Within the magnetometer, the relative orientations of the respective X, Y and Z axes detectors are maintained by a package in which all detectors are mounted on a single assembly with the Z axis sensor displaced and held orthogonal to the other two sensors by potting material. Shorting bars on respective barber pole structures are provided with a geometry that allows for closer placement of adjacent barber poles to one another. The barber pole structures are deposited in a nested orientation which provides for balanced resistance legs in a Wheatstone bridge construction.

Claims

1. A method of operating an electronic magnetic field measuring device comprising a plurality of anisotropic magnetoresistive (AMR) sensors, the method comprising:

realigning a respective magnetic domain orientation of each AMR sensor in only one direction; and

subsequent to the realigning of the respective magnetic domain orientation of each AMR sensor, detecting an output signal from the plurality of AMR sensors, the output signal being representative of a local magnetic field.

2. The method of claim 1, further comprising:

detecting a maximum value Vmax for the output signal since last realigning the magnetic domain orientations;

detecting a minimum value Vmin for the output signal since last realigning the magnetic domain orientations; and

comparing (Vmax+Vmin)/2 to a predetermined value PV to determine whether or not the realigning step should be repeated.

3. The method of claim 2, wherein comparing further comprises:

implementing a next realignments step if (Vmax+Vmin)/2 is greater than the predetermined value PV.

4. The method of claim 1, further comprising:

implementing a next realignments step a predetermined amount of time after the prior realignment step.

5. The method of claim 1, wherein the realigning step comprises:

passing a first current in a first direction through a first conductor positioned near the plurality of AMR sensors,

wherein a first magnitude and a first duration of the first current are chosen to sufficiently realign the magnetic domain orientation of each AMR sensor.

6. The method of claim 5, further comprising:

orienting the first direction of the first current to pass each AMR sensor substantially perpendicular relative to a longitudinal direction of each respective AMR sensor.

7. An electronic magnetic field measuring device, comprising:

a planar coil arranged in a spiral, the planar coil having an input and an output, and first and second leg portions, and the planar coil arranged in a first plane of the device;

a first plurality of barber pole structures, each barber pole structure of a first polarity, coupled in electrical series with another by a respective trace of a first plurality of conductive traces located between adjacent barber pole structures in the first plurality of series-connected barber pole structures; and

a second plurality of barber pole structures, each barber pole structure of a second polarity, coupled in electrical series with another by a respective trace of a second plurality of conductive traces located between adjacent barber pole structures in the second plurality of series-connected barber pole structures,

wherein the first and second pluralities of series-connected barber pole structures are arranged in a second plane of the device different from the first plane,

wherein the first and second pluralities of series-connected barber pole structures are disposed above only the first leg portion of the planar coil,

wherein the first and second pluralities of series-connected barber pole structures are arranged parallel with one another, and

wherein at least one trace of the first plurality of conductive traces and at least one trace of the second plurality of conductive traces are nested with one another.

8. The electronic magnetic field measuring device of claim 7, further comprising:

a third plurality of barber pole structures, each barber pole structure of a first polarity, coupled in electrical series with another by a respective trace of a third plurality of conductive traces located between adjacent barber pole structures in the third plurality of series-connected barber pole structures; and

a fourth plurality of barber pole structures, each barber pole structure of a second polarity, coupled in electrical series with another by a respective trace of a fourth plurality of conductive trace located between adjacent barber pole structures in the fourth plurality of series-connected barber pole structures,

wherein the third and fourth pluralities of barber pole structures are arranged in the second plane of the device,

wherein the third and fourth pluralities of series-connected barber pole structures are disposed above only the second leg portion of the planar coil,

wherein the third and fourth pluralities of series-connected barber pole structures are arranged parallel with one another,

wherein at least one trace of the third plurality of conductive traces and at least one trace of the fourth plurality of conductive traces are nested with one another, and

wherein the first, second, third and fourth pluralities of series-connected barber pole structures are coupled to one another to provide, respectively, first, second, third and fourth legs of a Wheatstone bridge circuit.

9. The measuring device of claim 8, further comprising:

at least one additional conductive trace, coupled to at least one of the first, second, third and fourth pluralities of series-connected barber pole structures, and configured to adjust or balance a total amount of resistance in the legs of the Wheatstone bridge circuit.

10. The measuring device of claim 7, wherein:

each of the first plurality of barber pole structures comprises a first permalloy portion and a plurality of shorting bars oriented at a first angle on the first permalloy portion; and

each of the second plurality of barber pole structures comprises a second permalloy portion, separate from the first permalloy portion, and a second plurality of shorting bars oriented at a second angle on the second permalloy portion,

wherein each shorting bar of the first and second pluralities of shorting bars has a same first geometry, and

wherein the first geometry comprises a rectangle with a pair of alternate and opposite clipped corners.

11. An electronic magnetic field measuring device, comprising:

a first barber pole structure including a first permalloy portion and a plurality of shorting bars oriented at a first angle on the first permalloy portion; and

a second barber pole structure including a second permalloy portion, separate from the first permalloy portion, and a second plurality of shorting bars oriented at a second angle on the second permalloy portion,

wherein each shorting bar of the first and second pluralities of shorting bars has a same first geometry, and

wherein the first geometry comprises a rectangle with a pair of alternate and opposite clipped corners.

12. An electronic magnetic field measuring device, comprising:

a flexible substrate with conductive interconnect traces, the flexible substrate including a first portion and a hingeable tab portion;

an ASIC module mounted on the first portion of the flexible substrate;

a first magnetic field sensor mounted on the first portion of the flexible substrate;

a second magnetic field sensor mounted on the first portion of the flexible substrate; and

a third magnetic field sensor mounted on the hingeable tab portion of the flexible substrate.

13. The measuring device of claim 12, further comprising:

potting material applied to the flexible substrate to hold the hingeable tab portion substantially perpendicular with respect to the first portion.

14. The measuring device of claim 13, wherein:

the third magnetic field sensor is configured to measure a magnetic field on an axis orthogonal to the first portion when the hingeable tab portion is held substantially perpendicular to the first portion.

15. The measuring device of claim 12 wherein each of the first, second and third magnetic field sensors comprises:

a planar coil arranged in a spiral, the planar coil having an input and an output, and first and second leg portions, and the planar coil arranged in a first plane of the device;

a first plurality of barber pole structures, each barber pole structure of a first polarity, coupled in electrical series with another by a respective trace of a first plurality of conductive traces located between adjacent barber pole structures in the first plurality of series-connected barber pole structures; and

a second plurality of barber pole structures, each barber pole structure of a second polarity, coupled in electrical series with another by a respective trace of a second plurality of conductive traces located between adjacent barber pole structures in the second plurality of series-connected barber pole structures,

wherein the first and second pluralities of series-connected barber pole structures are arranged in a second plane of the device different from the first plane,

wherein the first and second pluralities of series-connected barber pole structures are disposed above only the first leg portion of the planar coil,

wherein the first and second pluralities of series-connected barber pole structures are arranged parallel with one another, and

wherein at least one trace of the first plurality of conductive traces and at least one trace of the second plurality of conductive traces are nested with one another.

16. The measuring device of claim 15, wherein:

each of the first plurality of barber pole structures comprises a first permalloy portion and a plurality of shorting bars oriented at a first angle on the first permalloy portion; and

each of the second plurality of barber pole structures comprises a second permalloy portion, separate from the first permalloy portion, and a second plurality of shorting bars oriented at a second angle on the second permalloy portion,

wherein each shorting bar of the first and second pluralities of shorting bars has a same first geometry, and

wherein the first geometry comprises a rectangle with a pair of alternate and opposite clipped corners.

17. The measuring device of claim 15, wherein each of the first, second and third magnetic field sensors further comprises:

a third plurality of barber pole structures, each barber pole structure of a first polarity, coupled in electrical series with another by a respective trace of a third plurality of conductive traces located between adjacent barber pole structures in the third plurality of series-connected barber pole structures; and

a fourth plurality of barber pole structures, each barber pole structure of a second polarity, coupled in electrical series with another by a respective trace of a fourth plurality of conductive trace located between adjacent barber pole structures in the fourth plurality of series-connected barber pole structures,

wherein the third and fourth pluralities of barber pole structures are arranged in the second plane of the device,

wherein the third and fourth pluralities of series-connected barber pole structures are disposed above only the second leg portion of the planar coil,

wherein the third and fourth pluralities of series-connected barber pole structures are arranged parallel with one another,

wherein at least one trace of the third plurality of conductive traces and at least one trace of the fourth plurality of conductive traces are nested with one another, and

wherein the first, second, third and fourth pluralities of series-connected barber pole structures are coupled to one another to provide, respectively, first, second, third and fourth legs of a Wheatstone bridge circuit.

18. The measuring device of claim 17, wherein each of the first, second and third magnetic field sensors further comprises:

at least one additional conductive trace, coupled to at least one of the first, second, third and fourth pluralities of series-connected barber pole structures, and configured to adjust or balance a total amount of resistance in the legs of the Wheatstone bridge circuit.

19. A method of manufacturing an electronic magnetic field measuring device, the method comprising:

providing a flexible substrate having a plurality of conductive traces, the flexible substrate including a first portion and a tab portion;

mounting an ASIC module on the first portion of the flexible substrate;

mounting first and second magnetic field sensors on the first portion of the flexible substrate;

mounting a third magnetic field sensor on the tab portion of the flexible substrate;

rendering the tab portion hingeably connected to the first portion; and

displacing the hingeably connected tab portion to be substantially perpendicular with respect to the first portion of the flexible circuit.

20. The method of claim 19, wherein rendering the tab portion hingeably connected to the first portion comprises:

excising the flexible substrate along a predefined line.

22. The method of claim 20, wherein each of the first, second and third magnetic field sensors has a respective measurement axis along which a magnetic field is measured, wherein mounting the first and second magnetic field sensors comprises:

placing the first and second magnetic field sensors on the first portion of the flexible substrate such that the respective measurement axes are orthogonal to one another; and

placing the third magnetic field sensor on the tab portion of the flexible substrate comprises orienting the respective measurement axis parallel to the respective measurement axis of one of the first and second magnetic field sensors.

21. The method of claim 21, further comprising:

providing potting material to the flexible substrate to maintain the tab portion substantially perpendicular to the first portion.