EC8073 Medical Electronics - Hints for Slow Learner Nadar Saraswathi College of Engineering and Technology, Theni, Tamilnadu, India.

1. N.Mathavan || AP – ECE – NSCET
ELECTRODES
Pickup the electrical signal of the body (Transducer, Amplifier)
1. Electrode Potential
2. Electrode Material & Paste
3. Types of Electrode
 Micro Electrodes
 Metal Micro Electrode or Metallic Electrode
 Micro Pipet (Non Metalic)
4. Depth and Needle Electrodes
5. Surface Electrodes
 Metal Plate Electrodes
 Suction Cup Electrode
 Adhesive Tape Electrode
 Multipoint Electrode
 Floating Electrode
6. Chemical Electrode
 pH Electrode
 pCO2 Electrode
 pO2 Electrode
Electrode Potential
Voltage developed between Electrode & Electrolyte
 Perfectly Polarized Electrode
 Perfectly Non Polarized Electrode
 Artifact
Electrode Material & Paste
To minimize the polarization, Silver – Silver Chloride (Ag Ag Cl)
Types of Electrode
1. Microelectrodes
Small Diameter, Will not damage any cell, for Cell size 50 microns—Electrode
size 0 to 5 microns used.

2. N.Mathavan || AP – ECE – NSCET
(a)Metal Electrodes
Electrolytically Etching, Fine Tungsten or
Stainless steel, used technique is Electro pointing
i. (b) Micropipet (Non Metal Electrodes)
Glass micropipette, tip diameter 1 microns, 3 M KCL filled
with an electrolyte, Thin flexible metal wire made up of Chloride
silver, Stainless steel or Tungsten.
2. Depth & Needle Electrode
For better performance need to advance the electrode
through the penetration
(a)Depth Electrode
Used to study the electrical activity of neurons,
Electrode Consist of bundle of Teflon insulated
Platinum (90%) – Iridium (10%),
Active area of Depth electrode is 0.5 mm2
.
(b) Needle Electrode
Used to record the Peripheral nerves
(Electroneurography), it is a Medicine
Dropper or Hypodermic needle.
3. Surface Electrode
Large area surface electrode used in ECG, Small area surface electrode used in EMG,
EEG, during long – term monitoring this method is used.
(a)Metal Plate Electrodes
 Rectangular (3.5cm x 5cm), Circular (4.75cm dia),
 German silver, Nickel Silver,
 Resistance value 2 to 10 Kilo ohms.
Micropipet (Non-Metal)
Bundle of Copper Wire

3. N.Mathavan || AP – ECE – NSCET
(b)Suction Electrodes
More Practical & Well Suited for
flat surface, Soft tissue of body, Physically Large.
(c)Adhesive tape Electrodes
Skin may squeeze electrode paste out,
to avoid this problem this method is used,
Consist of lightweight metallic screen
packed by a pad for electrode paste
Multipoint Electrode
 Practical electrode for ECG measurement,
 Contain 1000 fine active contact point,
 Subject has Hair on the region- no need to remove Hair.
Floating Electrodes
 Metal does not contact the subject directly,
 Electrolyte bridge used,
 Also Called Liquid junction electrode.
4. Chemical Electrode
Used to Measure pH & pO2 content of Blood
Used to Determine the Oxygen & CO2 content in the blood
(a)pH Electrode
The chemical balance of human body is identified by
the measurement of pH content of blood.
pH is <7 = Acidic, pH is >7 = Basic
Human body is slightly Basic
pH value of Venous blood = 7.35
pH value of Arterial blood = 7.40
The GLASS electrode are used here
(b)PCO2 electrode
It consist of standard glass
pH electrode covered with the
rubber membrane, permeable to CO2
(c)PO2 electrode
It consists of piece of Platinum
wire embedded in an insulating glass holder.
A voltage of 0.7v is applied; Reduction of O2 takes place at the platinum.