Tel: +31 (0) 541 534603


Water based EEG electrodes

Tired of using gel and scratching the patient's skin for performing an EEG? With TMSi's water based electrodes this is all in the past.

After a period of profound research we came up with a sensor that could measure EEG by just using plain (tap) water. Its specifications are excellent, and it is very comfortable to wear.

During the European BRAIN project, a completely new type of EEG sensor was developed. The goal was to make this EEG sensor easy to handle, quick to apply, comfortable to wear and yet have an excellent signal quality (in combination with TMSi amplifiers). 

A special housing with integrated AgCl pellet electrode was used as the main component of the new sensor. The sensor housing can contain a sponge that is soaked with water. The sponge and the water make contact with the skin to measure EEG. In order to increase the comfort, and to decrease movement artifacts the sensor housing is inserted in a rubber fitting, integrated into a type of headcap. For the measurement of BCI signals, we further designed a new headwrap that is very quick and easy to apply. This headwrap contains a number of sensor fittings, in which the sensors are mounted. The fitting has a rubber ring, preventing the sensor to dry out quickly, but more important to prevent the sensor from moving with respect to the skin. In this manner a double function has been achieved. The fitting is produced from a soft type of rubber, and is very comfortable to wear.

The new electrodes were compared with standard Ag/AgCl gel based electrodes in a simulation environment. A towel soaked with seawater was used to measure the noise of both electrodes and amplifier. The noise of the amplifier is known, so we have a good estimate of the noise specifications of the water electrodes, as well as an impression about the DC stability of the electrode offset.

The tests have shown that the DC stability of the water electrodes is slightly better than that of the EEG cup electrodes, and the noise is a little bit lower. In the frequency band 1-300 Hz we see a noise of 0,79 μVrms.

Water electrodes are already being used in different applications, for example in Brain-Computer Interface (BCI) or Event-Related Potentials (ERP).

    • Setting-up a 32-channel EEG within a few minutes.

    • Very comfortable to wear.

    • No gel is required, only plain tap water.

    • No scratching of the skin is required.

    • You can measure 6-8 hours without losing signal quality.

For more information, please contact us:

Contact us  Tel: +31 (0) 541 534603


Zutphenstraat 57
7575 EJ Oldenzaal
+31 (0) 541534603




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