Unit-II Bio Signal Characteristics and Electrode configurations

Prepared By

Dr.K.HelenPrabha, HOD/ECE

Mr.P.Arul, Assistant Professor

ECG Electro-Cardiogram- Heart activity

EEG Electro-Encephalogram- Brain Signals

EMG Electro-Myogram - Muscle movement

EOG Electro-Oculogram - Eye movement

GSR Galvanic Skin Response

● Measured with electrodes:skin-electrode interface: Ions <--> Electrodes

Breathing, temperature, movement etc.

● Measured with other sensors / transducers:

Types of Bio electric signals

Primary Characteristics of Bio electric signals

Parameter Frequency range Amplitude Type of

Electrode

Electrocardiogrpahy

(ECG)

0.05 to 120 Hz 0.1 to 5µV

1µV

Surface

Electroencephalography

(EEG)

0.1 to 100 Hz 2 to 200µV

50µV

Scalp

Electromyography

(EMG)

5 to 2000 Hz 0.1 to 5µV Needle

Electroretinography

(ERG)

Dc to 20Hz 0.5 to 1µV Contact

Electro-oculography

(EOG)

Dc to 100 Hz 10 to

3500µV

Contact

ECG – Electrocardiogram

Standardised electrode positions

1. Bipolar limb leads(or) standard leads

2. Augmented unipolar limb leads

3. Chest leads(or) precordial leads

4. Frank lead system(or) corrected

orthogonal leads

Augmented voltage

aVR = -VI - VIII / 2

aVL = VI - VII / 2

aVR = VII - VI / 2

ECG: Heart- vector, QRS Complex

ECG - applications

● Diagnostics

● Functional analysis

● Implants (pace maker)

● Biofeedback (Heartrate variability, HRV)

● Peak Performacne Training, Monitoring

EMG - Electromyogram

EMG surface (glue-) electrodes EMG - signal (up to 3mV, 1kHz)

EMG electrodes (passive)

EMG electrodes(active)

EMG electrodes(active)

Recording locations for facial EMG

Needle electrodes adhesive electrode

EMG activity: averaging absolute vaues

EMG - applications

● Rehabilitation

● Functional analysis

● active Prothetics, Orthesis

● Biomechanics, Sports medicine

EEG - Electroencephalogram

EEG Electrode – cap locations ofthe 10/20 system

Unipolar measurement( indifferential right ear electrode )

Bipolar measurement

EEG, dominant frequencies, < 300 uV

EEG, Alpha bursts when eyes closed, alpha desynchronisation when eyes opened

EEG - applications

● Diagnostics (Epilepsy, Oncology, ..)

● Cognitive Sciences

● Sleep Analysis

● Human Computer Interfaces (BCIs)

● Pharmacology

● Intensive Care, Monitoring

Summary bioelectric signals

Frequency Amplitude (mV)

ECG 0,2 – 300 0,1 - 3

EEG DC – 100 0,005 - 0,2

EEG (cortical) 10 – 100 0,015 - 0,3

EMG 10 – 1000 0,1 - 5

EMG (needle) 10 – 10000 0,05 - 5

EOG 0 – 30 0,1 - 2

Intracell. 0 – 10000 50 .. 130

Video Links:

EEG 10-20 Electrode System:

https://www.youtube.com/watch?v=YfjRhoC2V0E