BME 462Electrode selection, testing and

placement

Zexi Liu, Ashley Mulchrone, Yue Yin 09/30/2014

Electrode Selection

Dry-Contact and Noncontact Biopotential Electrodes:Methodological Review, Yu Mike Chi etc.

Wet Electrode• Reusable• Low-cost• Produce reliable signals in

different conditions• Adhesive material to lower skin

impedance, buffer electrode against mechanical motion

• Most common in clinical setting

Floating Electrode• Metal disk is recessed,

swimming in the electrolyte gel• It is not in contact with the skin• Reduces motion artifact

Dry Electrode

Flexible dry surface-electrodes for ECG long-term monitoring, Klaus-Peter Hoffmann and Roman Ruff

• Direct contact with skin• No electrolyte• Use moisture on skin• Work well for quick

measurement• Motion artifact

Ex. Polysiloxane framework with conductive nano-particle

Non-contact Electrode

Dry-Contact and Noncontact Biopotential Electrodes:Methodological Review, Yu Mike Chi etc.

• Gap between skin and sensor• No dielectric layer• Measure through hair, clothing

or air• A need to design amplifier to

acquire signals

Electrode Placement

• 3 Lead ECG

• Einthoven’s Triangle• 2 leads (3rd can be calculated)

• 4 electrodes

• Current Standard – any part of arms/legs below the shoulders and the gluteal fold• Shoulders and wrist are

approximately equal

Electrode Placement• Mason-Likar placement –

mainly used for exercise• Diminishes QRS complex• Rightward axial shifts

• Torso placement• Obscure myocardial infarction

(create or mask)

• Motion artifact – muscle noise• Bone• MuscleStandard Mason-Likar

http://pmj.bmj.com/content/81/952/122.full