flux gate sensor analysis

8/13/2019 Flux Gate Sensor Analysis

1/17

Fluxgate Sensor Analysis

Dennis Steward

EM Application Engineer

Ansoft Corporation

Pittsburgh, PA


2/17

Flux Gate Sensor Basics

Simple Construction

Easily Saturable Core Drive Coil

Variable Inductance Function of Drive Current

Function of External

Magnetic Field

Drive Coil Core


3/17

Flux Gate Sensor Basics

Arrows

Indicate

Magnetization Direction

Typical B-H Curve

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

-8.0E+05 -6.0E+05 -4.0E+05 -2.0E+05 0.0E+00 2.0E+05 4.0E+05 6.0E+05 8.0E+05

H (A/m)

B(

T)

Saturated

Region

Low

Inductance

Saturated

Region

Low

Inductance

Saturated

Region

Linear

Region

High

Inductance

Sensor is Driven Between Linear and Saturated

Regions of the B-H Curve


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Flux Gate Sensor Applications

Arrows

Indicate

Magnetization Direction

Typical Flux Gate Sensor Applications include:

Proximity Sensing

Magnetic Field Measurement (Navigation, Geomagnetics) Speed & Position Sensing

Sensor has Linear Response Characteristic


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Maxwell Setup

How do I model a Flux Gate Sensor Using Maxwell?

Maxwell 3D

Optimetrics

SIMPLORER

Electromagentic Component

Analysis

Parametric Study of Component

Model Extraction

Initial Verification of Component

Full System Simulation using

Component


6/17

Parametric Analysis

SaturatedRegion

Linear Region

Curve Shifts Due To Influence of External Field


7/17

Export Component Model

Model Type

Coil Parameters

Extra Port (Bz)


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oi_p

oi_m Bz

Fluxgate_Sensor_1

E2

E1

R1

Sensor Current Response to a 2.5V, 100kHz Sinusoid

20.00m

-20.00m

0

-10.00m

10.00m

80.00u 100.00u85.00u 90.00u 95.00u

External Field Source

EMF := 0

Component Analysis

Current(A)

Time (s)

Positive andNegative Areas

are Equal

WaveformDistortion Caused

by traversing the

B-H Curve


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Component Analysis

Force = 3.72N

External Field Shifts Curve Positively or Negatively Positive and Negative Areas are No Longer Equal

Current(A)

Time (s)

Sensor Current Response to a 2.5V, 100kHz Sinusoid w/ External Field

25.0m

-25.0m

0

-20.0m

-15.0m

-10.0m

-5.0m

5.0m

10.0m

15.0m

20.0m

8.00e-005 9.60e-0058.20e-005 8.40e-005 8.60e-005 8.80e-005 9.00e-005 9.20e-005 9.40e-005


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Component AnalysisSensor Current Response to a 1.5V, 100kHz Sq. Wave w/ External Field

15.0m

-15.0m

0

-12.5m

-10.0m

-7.5m

-5.0m

-2.5m

2.5m

5.0m

7.5m

10.0m

12.5m

1.80e-004 2.00e-0041.83e-004 1.85e-004 1.88e-004 1.90e-004 1.93e-004 1.95e-004 1.98e-004

Sensor Behaves Similarly When Excited With a Square Wave

Current(A)

Time (s)


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Component Drive Signal

Flux Gate Sensor Drive Voltag6.00

0

2.50

5.00

0 2.00e-002.50e-00 5.00e-00 7.50e-00 1.00e-00 1.25e-00 1.50e-00

5V

Float GND Float

5V

Float GND Float

Three State Drive

5V

Ground

Float

Voltag

e(V)

Time (s)


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Component Drive Circuit

Drive Circuit Implementation

2 MOSFETS Are Fired alternately to create the 3 States

for the Flux Gate Sensor

oi_p

oi_m

Bz

EMSS - LINKEMSS - LINK

Fluxgate_Sensor_

Delay

GZ1

TRAPEZ


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oi_p

oi_m

Bz

Fluxgate_Sensor_1

Delay

GZ1

TRAPEZ1

A+

AM1

+

-

+

-

+

V

External Field Source

Integrator

Low Pass Filter

NSC_LM_741_1 NSC_LM_741_2

Sensor Drive

Output

System Analysis

Component Model

used in sensing circuit

Translated SPICE Models


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System Analysis System Output Voltage is Proportional To Magnitude of

External Field

Flux Gate Sensor System Output Voltage2.50

2.40

2.41

2.42

2.43

2.44

2.45

2.46

2.47

2.48

2.49

3.00e-003 3.80e-0033.50e-003

Volta

ge(V)

Time (s)


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System AnalysisFinal Differential Flux Gate Sensor Circuit Model

oi_p

oi_m

Bz

Fluxgate_Sensor_1

MOS1

MOS2

E2

A+

AM1

+

-

NSC_LM_7411

+

-

NSC_LM_7412

1k 665

2k

10n

68n

1n

220n

10k

2.5

2.5

+

V VM1

1k

E9

oi_p

oi_m

Bz

Fluxgate_Sensor_2

Sensor Drive

External Field Source 1

Low Pass Filter

Output

Integrator

External Field Source 2

5V Float_1

GroundFloat_2

State Machines Used to Fire MOSFETS


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System Analysis Differential Sensor Response

External Field For Sensor 2 Changes from 0G to 2G at 2ms

Output Voltage Shifts Downward to Reflect the Change

Differential Flux Gate Sensor System Output Voltage2.50

2.40

2.41

2.42

2.43

2.44

2.45

2.46

2.47

2.48

2.49

1.00e-003 4.00e-0032.00e-003 3.00e-003


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Conclusions

Using Maxwell 3D and Optimetrics, the electromagnetic

behavior of a Flux Gate Sensor may be accurately

analyzed.

A component model may be extracted from the Finite

Element Analysis which may then be used to examine

the impact of the component within a larger system.

SIMPLORER provides an environment where the finite

element component model may be combined with circuit,

block diagram, and state machine elements to study therole of the component in a complete system.

flux gate sensor analysis

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