EEG%20Monitoring%20System

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EEG Monitoring System

• The EEG Porto-Cap

Team 5 ENGN4017 - Engineering Design Autumn 1999
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Design Process

• Examine project domain
• EEG measurement systems
• Meet with intended customer
• Dr Richard Clark, Flinders University SA
• Identifying problems with existing skull cap
  system
• Requirements for new system were formulated
• Develop conceptual solutions to problems
• Brainstorming
• Project Decomposition
• Sub-system groups focussing on specific problems
• Integration
• System integration
• Presentation, Final Report

March
June
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What is EEG?

• EEG Electroencephalogram
• Measurement of brain wave patterns in hopes of
  understanding the mysteries of the mind.

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Problem Statement

The reliable measurement, over extended periods,
of scalp EEG on consecutive occasions, during
mental functions in everyday environments.
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Key Problem Areas

Issues that needed to be addressed in any new
system developed by the group

• Lack of repeatability
• Different Head Sizes
• Long setup times
• Difficulty with lengthy experiments
• Use of conductive gels
• Scalp abrasion
• Noise in signal
• Lack of portability/environmental constraints

In finding a solution, we have taken an ambitious
approach to solving these problems in a medical
research application
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Problem Decomposition

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Key Requirements
M e c h a n i c a l
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Cap Design
M e c h a n i c a l
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Positioning
M e c h a n i c a l

• Nasion/Ear reference points
• Adjustable straps for different head dimensions
  (53cm - 66cm)
• Electrodes retractable to suit

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Demonstration ofSkull Cap Setup . . .
M e c h a n i c a l
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Key Requirements
E l e c t r o d e
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Electrode Selection
E l e c t r o d e

• Silver/silver chloride selected
• Minimal polarisation characteristic
• Dry electrode used (no gel required)
• Uses local impedance converting amplifier
• Pellet electrode, 2mm diameter
• Small electrode size ensures good hair
  penetration and contact with scalp

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Irritation Issues
E l e c t r o d e

• Initial model- helmet supported by electrodes
• Prototype - straps support the load
• allows smaller electrodes to be used without
  increasing irritation
• straps allow for more comfortable fit
• No preparation or abrasion of skin surface
  required

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Cleaning
E l e c t r o d e

• Electrodes detachable for cleaning
• Cleaning processes include disinfecting and
  sterilisation via autoclave
• Use of two sets of electrodes allows continuous
  use

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Key Requirements
S i g n a l s
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Components
S i g n a l s
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Signal Flow
S i g n a l s
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Signal Flow
S i g n a l s
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Signal Flow
S i g n a l s
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Signal Flow
S i g n a l s
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Signal Flow
S i g n a l s
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Other Features
S i g n a l s

• EMF Shielding
• Faraday cage
• Cable shielding
• Auto-Zero Function
• Remove constant DC offset introduce by electronic
  components

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Areas of Further Research

• Gauging depth of electrodes
• Improving setup time
• Ag/AgCl dry electrodes
• Electrode polarisation
• Effectiveness of Faraday cage
• Noise analysis
• Artifacts from physiological rhythms

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Manufacturing Materials Cost

• Total - around US4k
• Mechanical - US100
• Electrode - US2300
• Signals - US1800
• Prototype materials - estimated US50k

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Why you should upgrade to the Porto-Cap . . .

• Wireless communication no huge cables to lug
  around, you are free to walk around the house
  just like with a cordless phone.
• Data recorded from each different electrode is
  clocked at exactly the same instant at last, a
  device which accurately maps which bits of your
  brain that werent working during that
  embarrassing moment.
• No scalp preparation required the feeling of
  blunt needles scraping your scalp will only be
  remembered in your nightmares.
• Porto-Cap uses dry electrodes only that gooey
  conducting paste can now be used as axle grease.
• Zero signal drift the amplifier and filter
  package has been hand picked so that the only
  interruptions during a testing period will
  involve rubble entering your building.
• Eight selectable sampling frequencies if
  flexible data rates is you, then you wont die
  hungry when wearing the Porto-Cap.

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Conclusion

The EEG Porto-Cap successfully enables
repeatable and reliable measurements of EEG
signals. It achieves this with little discomfort,
no paste or gel and in conventional environments.
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Thank you for coming,we would like to take this
opportunity to answer any questions you may have.

Team 5 ENGN4017 - Engineering Design Autumn 1999