1. ECG

Electrocardiography is a signal analyzing process used to study the electrical activity of the human heart using three lead systems by the Einthoven triangle. Generally, the chest electrodes are placed on the reputed region of the ribs to measure the PQRST waveform for determining the condition of heart, the other method is by using the clamp or the button electrode is used placed on the arms and lower limbs of the patients to measures the heart activity.

2. EMG

Electromyography is a technique used to study the electrical activity of muscles; EMG results can make known the nerve dysfunction, muscle dysfunction, or the difficulty with nerve-to-muscle communication. Generally, a needle electrode is one of the best tools to measure the contraction and relaxation levels of the patients, using the electrodes the EMG machine shows the graph, sounds or numerical values that are then understand or diagnose the condition of the patient by the professionals.

3. EEG

Electroencephalography is a graphical representation procedure for studying the electrical activity of the human brain. The measure of EEG requires 16 to 20 electrodes attached to the patient’s scalp (head/skull) to determine changes in the brain activity by analyzing delta waves, theta waves, alpha waves, beta waves, and gamma waves, that might be useful in diagnosing the brain disorder, especially epilepsy or another seizure disorder, it also determines the brain tumor or dysfunction, stroke, and sleeping disorders.

4. ERG

Electroretinography is the measurable procedure to study the electrical activity of retina (innermost layer of the eye), it includes many parts some important parts are photoreceptor, inner retinal cells, ganglion cells, etc ERG machine produces the waveforms namely a-wave, b-wave, c-wave and d-wave for analyzing the condition of rods and cones, corneal positive deflection, condition of the retinal pigments, and off bipolar cells in the eye respectively by fERG (foveal ERG)) method or ffERG (full-field ERG) method.

5. EOG

Electrooculography is the methodology used to study the activity or response of the front and back of the human eye also determine the eye movements. The EOG is also used to determine the function of the pigment epithelium. Generally, two basic electrodes are placed above and below the eye or to the left or right of the eye, it will help the ophthalmologist to predict the patient's

discomfort in vision.