Why does the brain activity map show activiy when the headset is not on my head?

Insight and EPOC products use a special noise cancellation circuit which requires the two reference sensors to be connected to a human. When the headset is sitting on a bench, clearly this condition is not met and the electronics float on the room noise, which can be huge! EEG signals are measured in microvolts - that is, one millionth of a volt.

Any object in a normal 21st Century room oscillates in synch with the electrical power circuits, transformers, motors, power supplies, phones, wireless transmitters of all kinds and also massive electrostatic signals. The scale of these variations is huge - electrostatic signals can be 20,000 volts without any problem, room pickup can be several volts.

All of these signals mash up in the electronics and generate random noise in the circuits which can't be cancelled unless our noise circuits are properly connected. We disable the brain viz outputs and other detections unless there is a detectable contact quality signal somewhere, usually because the user is actually wearing it and it will perform properly when fitted.

Unfortunately the thing about random noise is that it tends to look a lot like just about anything else at some time or other, so the contact quality detectors will sometimes fire up randomly as well and the application will show activity. The headset will work perfectly when fitted, but randomly when the noise cancellation circuit is disconnected. It is not a sign of a faulty headset. Every known EEG system including $60,000 medical units will behave the same way.

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