The electroencephalogram or EEG is related to the brain, and the electrocardiogram or ECG is related to the heart. Electrocardiogram (ECG), electroencephalogram (EEG), electromyography (EMG), and electrooculogram (EOG) can all measure bioelectric potential, which is the electrical output of human activity, however, the amplitude and bandwidth of the measurement vary depending on these. This table shows the value of each biopotential group according to the article “Biopotential and Electrophysiological Measurement” in the “Manual of Measurements, Instruments and Sensors”. The amplitude of all biopotential signals is very low, or even very low, so instrumentation amplifiers are usually used to obtain consistent low-noise signals. An additional requirement for EOG measurement is a very good low frequency response, even DC response.
| Source | Amplitude (mV) | Bandwidth (Hz) |
| ECG | 1-5 | 0.05-100 |
| EEG | 0.001-0.01 | 0.5-40 |
| EMG | 1-10 | 20-2000 |
| EOG | 0.01-0.1 | dc-10 |
The electrocardiogram determines heart activity by measuring signals from electrodes placed on the torso, arms, and legs; in contrast, several EEG electrodes are evenly attached to the forehead, and the ears are used as a reference for monitoring brain activity. EEG is mainly used to diagnose epilepsy, infections, tumors, degenerative diseases and metabolic disorders that may affect the brain; on the contrary, ECG is used to determine the heart rate, the position of the heart cavity and whether there is any damage to the heart. The ECG helps to identify a person Are there any heart problems.
Electrode pairs are used for specific muscles, and a separate position is used as a reference for EMG measurement. Finally, eye movement is measured by electrodes placed above, below, and to the side of each eye. In fact, measuring the retina in the eye produces another type of measurement called electroretinogram or ERG.
