Reasoning for the balance bar:

In a normal work environment, typical noise coupled into the electrode cables is larger than the EEG signal by a factor between 100 and 10,000. Fortunately, this noise is coupled into all electrode wires with almost the same level. The EEG NeuroAmp has therefore a differential amplifier so that most of this noise is cancelled out. This cancelling works better the more equal the noise levels are. In order to achieve that, the electrode cables should be braided or be kept near each other by other means (e.g. spiral tube), and the impedances to the scalp should match.


Importance of good balance:

If the electrode impedances show green lights, i.e. good contacts, the balance reading might be less important. So, 'green' electrode contacts and a red balance might be tolerable in most work environments. However, if there is a strong noise source such as a defective electrical machine or a nearby railway, a good balance reading becomes indispensable.


Low frequency work:

If you work at frequencies below 1 Hz and use electrodes other than sintered AgCl electrodes, a good matching as well as very good and stable electrode contacts are very important, too.