Where and how to place the headband?
The headband is symmetrical, there is no up or down side. When used on the right side the cable should go over the right ear (to be away from the face). When used on the left the cable should go over the left ear. The headband can be used anywhere on the head as long as the optodes can be against the skin.
How and how long to charge the HEG sensor?
The HEG sensor has to be turned off in order to charge it. Charging for about 10 hours (for example overnight) will replenish the battery.
The battery should not be drained completely as this may reduce the capacity of the battery.
For how long can I use the HEG sensor after charging?
The battery has enough capacity for several days of full-time usage.