Electrical Safety BiomedE / EECS 458 Reading: Webster, Chapter 14.
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Transcript of Electrical Safety BiomedE / EECS 458 Reading: Webster, Chapter 14.
![Page 1: Electrical Safety BiomedE / EECS 458 Reading: Webster, Chapter 14.](https://reader038.fdocuments.in/reader038/viewer/2022102808/56649c755503460f94928b9a/html5/thumbnails/1.jpg)
Electrical Safety
BiomedE / EECS 458Reading: Webster, Chapter 14
![Page 2: Electrical Safety BiomedE / EECS 458 Reading: Webster, Chapter 14.](https://reader038.fdocuments.in/reader038/viewer/2022102808/56649c755503460f94928b9a/html5/thumbnails/2.jpg)
Electrical Currents in body
Vstim ~
Rskin Rskin
Rinternal
Three phenomena are possible through electrical currents
• Electrical stimulation of excitable tissue (nerve & muscle)
• Resistive heating of tissue
• Electrochemical burns and tissue damage
![Page 3: Electrical Safety BiomedE / EECS 458 Reading: Webster, Chapter 14.](https://reader038.fdocuments.in/reader038/viewer/2022102808/56649c755503460f94928b9a/html5/thumbnails/3.jpg)
Physiological effects of electricity
Conditions: 70-kg human, moistened hands, AGW #8 copper wire
![Page 4: Electrical Safety BiomedE / EECS 458 Reading: Webster, Chapter 14.](https://reader038.fdocuments.in/reader038/viewer/2022102808/56649c755503460f94928b9a/html5/thumbnails/4.jpg)
Variability of Perception Thresholds and Let-go Currents
Physiological effects of electrical shocks depend on body size ( among other factors)
![Page 5: Electrical Safety BiomedE / EECS 458 Reading: Webster, Chapter 14.](https://reader038.fdocuments.in/reader038/viewer/2022102808/56649c755503460f94928b9a/html5/thumbnails/5.jpg)
Let-go Current vs. Frequency
60 Hz
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Fibrillation Current vs. Shock Duration
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Effects of Entry Points on Current Distribution
Microshocks -- currents as low as 20 uA can induce cardiac fibrillation
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Electric-power Distribution
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Macroshock Hazards
Most instruments have grounded or non-conductive cases
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Leakage-current Pathways
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Ground-fault Currents
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“Equivalent Resistance Guy”
Skin surface
Sub-dermal surface
Skin resistance (15 k Ω to 1 MΩ/cm2)
Internal body resistance (100-200 Ω -- limb, trunk)
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Erg in intensive care
•ECG monitor (lead I)
•EEG monitor (single lead)
•Catheter in right arm for IV drug infusion through automated system
Each system is plugged into a separate wall outlet
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Erg’s bedside schematic
Outlet 1 Outlet
2
Outlet 3
sigsig
sigsig
HN
G1G1
G3H N G2
G2
HN
~G3
EEGECG
Pump
![Page 15: Electrical Safety BiomedE / EECS 458 Reading: Webster, Chapter 14.](https://reader038.fdocuments.in/reader038/viewer/2022102808/56649c755503460f94928b9a/html5/thumbnails/15.jpg)
Erg’s bedside schematic
Outlet 1 Outlet
2
Outlet 3
sigsig
sigsig
HN
G1G1
G3 HN G2
G2
HN
~G3Vgl ~
Ground loop currents!!
EEGECG
Pump
![Page 16: Electrical Safety BiomedE / EECS 458 Reading: Webster, Chapter 14.](https://reader038.fdocuments.in/reader038/viewer/2022102808/56649c755503460f94928b9a/html5/thumbnails/16.jpg)
Erg’s bedside schematic
Outlet 1 Outlet
1
Outlet 1
sigsig
sigsig
HN
G1G1
G1 HN G1
G1
HN
~G1
Solution: Single power distribution node with a common ground
EEGECG
Pump
![Page 17: Electrical Safety BiomedE / EECS 458 Reading: Webster, Chapter 14.](https://reader038.fdocuments.in/reader038/viewer/2022102808/56649c755503460f94928b9a/html5/thumbnails/17.jpg)
Grounding System
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Isolated Amplifier