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Quantum Well Hall Effect Sensor Based Handheld Magnetic Scanner with Programmable Electromagnetic Coil for Non- Destructive Testing of Ferromagnetic and Non-Ferromagnetic Materials Authors: Firew Abera Biruu MEng MIET Dr Ertan Balaban Dr

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SLIDE 1

13th September 2016

Quantum Well Hall Effect Sensor Based Handheld Magnetic Scanner with Programmable Electromagnetic Coil for Non- Destructive Testing of Ferromagnetic and Non-Ferromagnetic Materials

Authors: Firew Abera Biruu MEng MIET Dr Ertan Balaban Dr Ehsan Ahmad Professor Mohamed Missous

55th Annual Conference of the British Institute for Non-Destructive Testing Nottingham, United Kingdom September 2016

University of Manchester

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SLIDE 2

13th September 2016

  • Introduction
  • QWHE Sensors
  • Design and Fabrication of a proposed Handheld Scanner
  • Preliminary Test Results
  • Conclusion

Talk Outline

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SLIDE 3

13th September 2016

Defects in engineering materials happen at anytime during their life span in sizes not visible to human eye. Due to this, they can progress undetected, without specialist monitoring or testing devices, to cause catastrophic failure of a given system. Most relevant testing methods studied here are non destructive and provide an invaluable alterative to destructive testing systems, where a material undergoes intentional destruction and could not be recovered. Such testing devices relate to particular scientific principles. Likewise, testing systems studied here are based

  • n electromagnetic principles.

Beside their positive advantages and unique solution to materials testing, some

  • f these methods are bulky and use hazardous chemicals. Some systems, like

silicon based Hall effect sensors have low sensitivities and consume high power.

Introduction

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SLIDE 4

13th September 2016

A new approach that is already ongoing at the University of Manchester is the use of a new class of extremely sensitive Hall Effect sensors called Quantum Well Hall Effect (QWHE) sensors to detect stray (nanoTesla) magnetic field signatures. The research presented here has the potential to contribute greatly to future NDT and contactless sensing systems.

Introduction

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SLIDE 5

13th September 2016 Fig 5. Magnetic field sensor spectrum: > 1010

QWHE sensors:

  • Have higher

sensitivities than commercial alternatives

  • Operate on a very wide

dynamic range of field

5

Quantum Well Hall Effect Sensors

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SLIDE 6

13th September 2016

Many devices have been developed to inspect defects based

  • n

electromagnetic principles. Present technologies perform a one dimensional magnetic field measurement. Methods like MFL and ACFM are usually performed separately. The possibility of capturing 2D magnetic field data would help to investigate the defect more deeply. Integrating a programmable magnetic field illumination source helps to perform both MFL and ACFM like techniques allowing both magnetic and non magnetic materials to be inspected.

2D Magnetic Fields Imaging

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SLIDE 7

13th September 2016 Fig 6. Block diagram of Handheld Scanner (HHS)

Design and Fabrication

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SLIDE 8

13th September 2016

Sensor Arrays and Orientation

1x8 QWHE sensor array with 4mm pitch

Sensors on the vertical array detect magnetic field parallel to the test piece but perpendicular to πΆπ‘Ž . This magnetic field can either be πΆπ‘Œ 𝑝𝑠 𝐢𝑍 Sensors on the horizontal array detect magnetic field normal to the surface of the test piece, πΆπ‘Ž

Fig 7. P2A sensor array Fig 8. Sensor array orientation

Design and Fabrication

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SLIDE 9

13th September 2016

Amplification Gain π‘Š

𝐡𝐸𝐷_π‘›π‘—π‘œ = βˆ†π‘Šπ‘ π‘“π‘” 𝐡𝐸𝐷 π‘ π‘“π‘‘π‘π‘šπ‘£π‘’π‘—π‘π‘œ = 5π‘Š 218 = 19.07πœˆπ‘Š

π‘Š

𝐼 = 𝐿𝐢𝐽 = 0.17 mV mT 𝑛𝐡 Γ— 1𝑛A Γ— 100π‘œπ‘ˆ =

17π‘œV

π»π‘π‘—π‘œ = π‘Š

𝐡𝐸𝐷_π‘›π‘—π‘œ

π‘Š

𝐼

= 19.07πœˆπ‘Š 17 π‘œV = 1121.97 β‰ˆ 1122

Fig 9. For 1mA biasing current, the noise floor is 100nT at 10kHz A fist stage gain of 250 using an INA163A low noise amplifier before switching and a second stage gain of up to 176 is handled by a programmable gain amplifier

Design and Fabrication

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SLIDE 10

13th September 2016

Design of Electromagnet Coils

Fig 10. vertical orientation illuminates the test piece with part of the strong internal magnetic field. Left(top): Simulation result, Left(bottom) Programmable Electromagnetic Driver.

10

Design and Fabrication

The maximum magnetic field that can be generated in the coil, also shown in figure 11, can be calculated from ampere’s law, using the calculated effective permeability, as:

𝐢𝑛𝑏𝑦 =

𝜈0πœˆπ‘“π‘”π‘”π‘‚π½ 𝑀

=

4πœŒΓ—10βˆ’7Γ—20.17Γ—31Γ—3𝐡 28Γ—10βˆ’3

= 84.18 π‘›π‘ˆ

Figure 11. Magnetic Field along the axis of designed electromagnetic coil

πœˆπ‘“π‘”π‘” =

2000 1+( 2Γ—10βˆ’3𝑛

81.5Γ—10βˆ’3𝑛)2000 = 20.17

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SLIDE 11

13th September 2016

Preliminary Tests

11

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SLIDE 12

13th September 2016

Coil Parameters

  • Wire diameter = 0.71mm (copper)
  • Number of turns = 31 per layer
  • Number of layers = 3

Test Material

  • Material: ferromagnetic steel
  • Groove dimension = 15mm x 10mm x 10mm
  • Grids shown = 5mm by 5mm

Measurements are taken using QWHE magnetometer

  • X direction +

Y direction

  • +

+Z direction perpendicular and

  • ut of this page

DC Magnetic Field Experimental Test Results

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SLIDE 13

13th September 2016 Simulated B-Field

  • 10.0
  • 7.5
  • 5.0
  • 2.5

0.0 2.5 5.0 7.5 10.0 12.5

  • 25
  • 20
  • 15
  • 10
  • 5

5 10 15 20 25 Magnetic Field Bz [mT] Distance Along X- Direction [mm] Magnetic Field (BZ) at 3A Fig 12. Z Component DC Magnetic Field Measurement

55mm

Z-component Magnetic field measurement was made along centre line of the groove in the X-axis direction. The region in between the red dotted lines is where the actual β€˜defect’ groove is. The existence of the defect is indicated by the experimental curve in blue, which is also accurately shown by simulated curve. The dimension of the groove in the x-axis is an indication of how wide the groove is.

DC Magnetic Field Experimental Test Results

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SLIDE 14

13th September 2016

0.0 0.5 1.0 1.5 2.0 2.5

  • 20
  • 15
  • 10
  • 5

5 10 15 20

Magnetic Field (Simulated) [mT] Distance Along X- Direction [mm]

Simulated Bx Field

The region in between the dotted lines indicate where the actual defect is. In this region no field measurement is expected as the magnetic flux goes around the defect as there is very low magnetic permeability. Simulated results show the expected curve. The experimental measurement curve, shows the existence of the defect (indicated by a shallow deep).

DC Magnetic Field Experimental Test Results

Fig 13. Bx Component DC Magnetic Field Measurement [left] and Simulated result [right] 0.0 0.5 1.0 1.5 2.0 2.5

  • 20
  • 15
  • 10
  • 5

5 10 15 20

Magnetic Field (Measured) [mT] Distance Along X- Direction

Magnetic Field (B_X) at 3A [mT]

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SLIDE 15

13th September 2016

2 3 4 5 6 7 8 9 10

  • 25
  • 20
  • 15
  • 10
  • 5

5 10 15 20 25

Magnetic Field [mT] Distance Along X- Direction [mm]

Magnetic Field (BXZ) at 3A [mT]

The graph above is generated taking the resultant of Bx and Bz, i.e., (Bπ‘Œπ‘Ž =

Bπ‘Œ

2 + Bπ‘Ž 2). The region in

between the red dotted lines indicate how wide the groove is. While the defect is detected β€˜slightly’ on the separately β€˜Measured Bx’ and β€˜Measured Bz’ curves, combining the two results in such a way can enhance defect detection and defect sizing. This approach can be implemented in the handheld scanner to both scan defects and estimate their dimensions.

DC Magnetic Field Experimental Test Results

Fig 14. Combined curve, resultant of of Bx and Bz components

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SLIDE 16

13th September 2016

Coil Parameters

  • Wire diameter = 0.71mm (copper)
  • Number of turns = 31 per layer
  • Number of layers = 3

Test Material

  • Material: Aluminium Sheet
  • Through hole diameter = 20mm
  • Grids shown = 10mm x 10mm
  • X direction +

Y direction

  • +

+Z direction perpendicular and

  • ut of this page

AC Magnetic Field Experimental Test Results

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SLIDE 17

13th September 2016

The Bz plot clearly shows the defect position, the region of plot shown between the dotted lines in the left figure indicates very close dimension of the through hole diameter. Bx values at the center top of the 20mm through hole also drop to near zero as eddy currents make their way around it when they encounter the through hole. As a result a weak magnetic field is registered at the center of the through hole pointing the existance of a β€˜defect’

AC Magnetic Field Experimental Test Results

Fig 15. AC magnetic field experimental results

  • f Bx and Bz components

0.5 5 50

  • 70
  • 60
  • 50
  • 40
  • 30
  • 20
  • 10

10 20 30 40 50 60 70

Magnetic Fild (Bz) [mT] Distance Along X axis through Centerline of the through hole [mm]

Bz at 500Hz Bz at 1kHz Bz at 2kHz

1 10

  • 70
  • 60
  • 50
  • 40
  • 30
  • 20
  • 10

10 20 30 40 50 60 70

Magnetic Fild (Bx) [mT] Distance Along X axis through Centerline of the through hole [mm]

Bx at 500Hz Bx at 1kHz Bx at 2kHz

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SLIDE 18

13th September 2016

Significant difference of the simulated and measured result curves is that Bx measurement is not taken at the magnets location, as it is physically not possible but assumption

  • f

dominant Bz field is taken and Bx is set to zero. Rapid drop of Bx in the simulated result, shown in dotted ellipses, support this claim. Measurements show close resemblance with simulated results promising continual improvement in measurement and data processing for more accurate defect detection by QWHE sensors

AC Magnetic Field Experimental Test Results

Fig 16. AC magnetic field comparison of experimental and simulated results

1 10

  • 70
  • 60
  • 50
  • 40
  • 30
  • 20
  • 10

10 20 30 40 50 60 70

Magnetic Fild (Bx) [mT]

Distance Along X axis through Centerline of the through hole [mm] Bx at 500Hz Bx at 1kHz Bx at 2kHz 1 10 100

  • 70
  • 60
  • 50
  • 40
  • 30
  • 20
  • 10

10 20 30 40 50 60 70

Magnetic Field (Bx) Simulated [mT]

Distance Along X axis through Centre line of the through hole [mm] B-Field [500], x/real B-Field [1000], x/real B-Field [2000], x/real

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SLIDE 19

13th September 2016

Fig 17. Initial test of the handheld scanner for magnetic field reversal

Magnetic Field Reversal Test Using HHS

  • Magnetic field reversal

from β€˜south’ magnetic pole to β€˜north’ where the curve intersects zero, is shown on both vertical and horizontal sensor arrays

  • The deep spot in the

β€˜Combined’ curve at 15mm position indicates where the field reversal takes place

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SLIDE 20

13th September 2016

  • A QWHE sensor based handheld scanner utilizing two arrays of such

sensors was successfully designed and built.

  • Preliminary tests have been carried out out to verify that the device was

working properly and successful preliminary results are reported.

  • A programmable

electromagnetic coil was designed and is in its programming and testing stages.

  • Future improvement include programmable electromagnetic coils and

programming stages so that it can be used to illuminate both DC and AC magnetic field from on board power source.

  • The handheld scanner will play important roles in speeding up testing at

increased sensitivity.

Summary

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SLIDE 21

13th September 2016

Thank You

The project is part funded by EPSRC and STFC for which the authors are very grateful (STFC-ST/L000040/1 β€œHIGH RESOLUTION 2D MAGNETIC VISION-B-CAM” and EPSRC- EP/LO22125/1 β€œUK RESEARCH CENTE IN NON- DESTRUCTIVE EVALUATION (RCNDT)”)