What Is an EEG Machine? Uses, Types and Benefits

An electroencephalography (EEG) machine records the small electrical signals produced by the brain’s cortex. Electrodes on the scalp pick up voltage changes of a few microvolts. The amplifier boosts these signals and the software shows them as waveforms that a neurologist reads.

How an EEG machine works

1. Electrodes are placed using the international 10-20 system, which spaces them at 10% and 20% intervals of skull measurements.
2. The amplifier (headbox) amplifies the tiny signals and filters out noise.
3. Analogue-to-digital conversion turns the signal into digital data. Higher resolution (14–16 bit) and sampling rates (500–1024 Hz) preserve detail.
4. Software displays montages and filters, adds event markers and produces reports. Advanced packages add brain mapping and spectral analysis.

Types of EEG systems

• Routine digital EEG (19–24 channels). The everyday OPD test, typically 20–40 minutes. A 24 channel EEG covers this.
• Sleep-deprived EEG. The same equipment, recorded after sleep deprivation to increase the chance of capturing abnormalities.
• Ambulatory EEG. A portable recorder worn at home for 24–72 hours.
• Video EEG. Synchronised video with EEG, used in epilepsy monitoring units. See 32 channel video EEG.
• High-density EEG (64+ channels). Used for source localisation and research. See 64 channel EEG.

Clinical uses of EEG

• Epilepsy. Supports the diagnosis, helps classify seizure types and guides treatment decisions.
• ICU and emergency. Detects non-convulsive status epilepticus and monitors patients after cardiac arrest or with encephalopathy.
• Encephalopathy and altered consciousness. Helps assess metabolic, infectious and toxic causes.
• Sleep medicine. Part of polysomnography.
• Psychiatry and research. Used in neurofeedback, quantitative EEG and cognitive studies.

Benefits of digital EEG

• Non-invasive and safe for all ages.
• Inexpensive compared with imaging.
• High time resolution, measured in milliseconds.
• Digital storage, re-montaging and remote review.
• Portable systems allow bedside testing in the ICU.

Limitations to understand

EEG records surface cortical activity, so deep sources may not show. A normal recording between seizures does not exclude epilepsy. Results also depend on good electrode application and a technician trained to recognise artifacts. Read our guide on common EEG artifacts.

Choosing an EEG machine

Match the system to your caseload. Routine OPD work needs 24 channels; epilepsy work benefits from video; research may need 64 channels. Our EEG price guide compares models and costs, and our team can arrange a demo anywhere in East and Northeast India.