To achieve great signal quality you need to minimise impedance between the gel sensor and the scalp. We recommend subjects should have their hair washed, but free from conditioner and other additives as these products can interfere with minimising impedances. It is recommended to have sufficient illumination when cleaning sensor positions and fitting the gel. The most effective method of achieving low impedance is to clean and abrade the skin under each electrode and then apply an electrolytic gel or paste. Any conductive gel can be used but some gels are better suited because of their viscosity or the EEG application for example in sleep studies it is important to use a gel that takes a long time to dry out.
The easycap multi-rodes can be used with both salty and salt-free electrolytes. Below are some of the available materials:
SuperVisc (clear, high-viscosity, salty)
Lectron III-10(clear, medium-viscosity, salty)
Abralyt HiCl(Abrasive, high-viscosity, salty)
Abralyt 2000(Abrasive, high-viscosity, non-salty)
Ten20 (Opaque, high-viscosity, salty)
Nuprep Gel (Abrasive, high viscosity, non-salty)
Wooden cotton swabs
Isopropyl alcohol >70%
Abrasive electrolyte gel such as Abralyt 2000
Conductive electrolyte gel such as SuperVisc or Ten20
Plastic syringe (20ml) without needle
tissues to remove excess gel
Please follow the outlined procedure below for all sensor locations, We recommend that you start this process with the reference sensors first before moving onto the other locations. You can fill the syringe ahead of time with the electrolyte gel, a 20ml syringe should contain enough gel for 30 electrodes.
Clean the Skin
Using a wooden cotton swab move the hair below the sensor opening to get clear access to the scalp. Then using the isopropyl alcohol on a cotton swab rotate tip gently to degrease the skin.
Abrade the skin
Using another cotton swab dip in the abrasive gel and again rotate in the sensor opening, be careful to not apply too much pressure to ensure this is painless and doesn't redden the skin.
Fill sensor with electrolyte
Now fill completely the sensor opening with electrolyte gel using a syringe, ensuring you have made contact between the scalp and the electrode. Most electrolytes take a few minutes to permeate the skin.