INTEGRATED FLUXGATE MAGNETIC GRADIENT SENSOR

• US 20160349334A1
• Filed: 05/24/2016
• Published: 12/01/2016
• Est. Priority Date: 05/27/2015
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments Deutschland Gesellschaft Mit Beschrã¤Nkter Haftung (Texas Instruments, Inc.)
• Inventors: SNOEIJ, Martijn Fridus, SCHFFER, Viola, HAUG, Gebhard
• Granted Patent: US 10,459,040 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 33/022 Measuring gradient
• CPC Class Codes: G01R 33/04 using the flux-gate principle

Abstract

An integrated fluxgate magnetic gradient sensor includes a common mode sensitive fluxgate magnetometer and a differential mode sensitive fluxgate magnetometer. The common mode sensitive fluxgate magnetometer includes a first core adjacent to a second core. The first and second cores are wrapped by a first excitation wire coil configured to receive an excitation current that affects a differential mode magnetic field. The differential mode sensitive fluxgate magnetometer includes a third core adjacent to the first core and a fourth core adjacent to the second core. The third and fourth cores are wrapped by a second excitation wire coil configured to receive an excitation current that affects a common mode magnetic field.

Claims

1. An integrated fluxgate magnetic gradient sensor, comprising:

a common mode sensitive fluxgate magnetometer including a first core adjacent to a second core, the first and second cores wrapped by a first excitation wire coil configured to receive an excitation current that affects a differential mode magnetic field; and

a differential mode sensitive fluxgate magnetometer including a third core adjacent to the first core and a fourth core adjacent to the second core, the third and fourth cores wrapped by a second excitation wire coil configured to receive an excitation current that affects a common mode magnetic field.

2. The integrated fluxgate magnetic gradient sensor of claim 1, wherein the common mode sensitive fluxgate magnetometer further includes a common mode sense wire coil configured to output a voltage proportional to a common mode magnetic field.

3. The integrated fluxgate magnetic gradient sensor of claim 2, wherein the voltage across the common mode sense wire coil corresponds to a sum of field change in the first and second cores of the common mode sensitive fluxgate magnetometer.

4. The integrated fluxgate magnetic gradient sensor of claim 1, wherein the differential mode sensitive fluxgate magnetometer further includes a differential mode sense wire coil configured to output a voltage proportional to a differential mode magnetic field.

5. The integrated fluxgate magnetic gradient sensor of claim 4, wherein the voltage across the differential mode sense wire coil corresponds to a difference in field changes in the third and fourth cores of the differential mode sensitive fluxgate magnetometer.

6. The integrated fluxgate magnetic gradient sensor of claim 1, further comprising a differential voltage driver coupled to the common mode sensitive fluxgate magnetometer and the differential mode sensitive fluxgate magnetometer and configured to drive a first compensation current through a first compensation wire coil wrapped around the first core and the second core and a second compensation wire coil wrapped around the third core and the fourth coil.

7. The integrated fluxgate magnetic gradient sensor of claim 6, further comprising a single-ended voltage driver coupled to the differential mode sensitive fluxgate magnetometer and configured to drive a second compensation current through the second compensation wire coil.

8. The integrated fluxgate magnetic gradient sensor of claim 7, wherein the common mode sensitive fluxgate magnetometer further includes a common mode sense wire coil and an input to the differential voltage driver is a voltage across the common mode sense wire coil.

9. The integrated fluxgate magnetic gradient sensor of claim 7, wherein the differential mode sensitive fluxgate magnetometer further includes a differential mode sense wire coil and an input to the single-ended voltage driver is a voltage across the differential mode sense wire coil.

10. The integrated fluxgate magnetic gradient sensor of claim 7, further comprising a shunt resistor coupled to the single-ended voltage driver and the second compensation wire coil.

11. A driver circuit, comprising:

a differential voltage driver configured to drive a differential voltage through a common mode sensitive fluxgate magnetometer and a differential mode sensitive fluxgate magnetometer; and

a single-ended voltage driver configured to drive a single-ended voltage through the differential mode sensitive fluxgate magnetometer;

wherein an input to the differential voltage driver is a voltage across a common mode sense wire coil included in the common mode sensitive fluxgate magnetometer and an input to the single-ended voltage driver is a voltage across a differential mode sense wire coil included in the differential mode sensitive fluxgate magnetometer.

12. The driver circuit of claim 11, further comprising a shunt resistor coupled to an output of the single-ended voltage driver and the differential mode sensitive fluxgate magnetometer.

13. The driver circuit of claim 11, wherein the differential voltage driver is configured to drive the differential voltage through the common mode sensitive fluxgate magnetometer by driving the differential voltage through a compensation wire coil wrapped around a magnetic core included in the common mode sensitive fluxgate magnetometer.

14. The driver circuit of claim 11, wherein the single-ended voltage driver is configured to drive the single-ended voltage through the differential mode sensitive fluxgate magnetometer by driving the single-ended voltage through a compensation wire coil wrapped around a magnetic core included in the differential mode sensitive fluxgate magnetometer.

15. The driver circuit of claim 11, wherein the differential voltage driver is coupled to the common mode sensitive fluxgate magnetometer and the differential mode sensitive fluxgate magnetometer in parallel.

16. A method of measuring a magnetic field gradient, comprising:

driving, by a differential voltage driver, a differential voltage through a common mode compensation wire coil wrapped around a first core and a second core;

driving the differential voltage through a differential mode compensation wire coil wrapped around a third core and a fourth core;

driving, by a single-ended voltage driver, a single-ended voltage through the differential mode compensation wire coil; and

sensing a magnetic field gradient voltage across a shunt resistor coupled to the single-ended voltage driver and the differential mode compensation wire coil.

17. The method of claim 16, further comprising:

sensing a common mode sense voltage across a common mode sense wire coil wrapped around the first and second cores;

inputting the common mode sense voltage into the differential voltage driver.

18. The method of claim 16, further comprising:

sensing a differential mode sense voltage across a common mode sense wire coil wrapped around the third and fourth cores;

inputting the differential mode sense voltage into the single-ended voltage driver.

19. The method of claim 16, wherein the first core is adjacent the second core, the third core is adjacent the first core, and the fourth core is adjacent the second core.

20. The method of claim 16, wherein the first, second, third, and fourth cores comprise a ferromagnetic material.