g.SAHARA: Specs & Features

g.SAHARA: active dry EEG electrode system

active dry EEG electrode system

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Normally, the electroencephalogram (EEG) is recorded from the surface of the head with gel based electrodes to get a low electrode-skin impedance. If passive electrodes are used, the skin must be abraded beforehand to reduce the impedance. With active electrodes, which contain an amplifier inside, the electrode gel is injected between the electrode material and the skin. This allows a faster montage of the electrode system.

One of the main advantages of gel based active electrodes is their robust behavior, but the main disadvantages are the long montage time and the need to wash the user's hair after the recording. g.tec thus developed a dry electrode system which does not require electrode gel, as shown in Figure 1. The g.SAHARA electrode system (patent pending) consists of an 8 pin electrode made of a special golden alloy. The pins have sufficient length to reach through the hair to the skin. The golden alloy and the 8 pins reduce the electrode-skin impedance. The electrode itself can be connected with a clip to the active electrode system on top of it.

g.SAHARa active dry EEG electrode
Rear view of the g.SAHARAelectrode.
Figure 1: g.SAHARA dry active electrode system Figure 2: 2nd generation of the g.GAMMAcap with highly optimized fit to the head and very narrow joints to maximize possible electrode locations.

EEG recordings are performed at frontal, central, parietal and occipital regions of the head, and therefore a mechanical system is required that holds the electrode to the skin with a constant pressure at every possible recording location. EEG electrodes are typically positioned according to the international 10/20 system. g.tec hence developed the 2nd generation of the g.GAMMAcap, with a total of 160 positions according to an extended 10/20 system, to allow a very flexible electrode montage, as shown in Figure 2. 

Product Highlights

  • The first and only dry electrode system that works for all frontal, central, occipital and parietal sites
  • The first dry active electrode already available on the market
  • The first and only dry system tested with all major BCI concepts in group studies with success
  • Cost range of an active EEG electrode
  • Captures the whole EEG frequency spectrum from 0.1-40 Hz
  • Perform EEG recordings without gel
  • Mount the cap in under one minute!
  • Washing hair is no longer required!
  • Able to pick up frequency spectra for P300, motor imagery and SSVEP based BCIs

More Product Details

The design of the g.SAHARA electrode system allows users to just plug the electrode and the clip into the cap at the desired location. The clip fits very well in the electrode and gives the electrode a perfect hold inside the cap.

g.SAHARA active dry EEG electrodes mounted to the 2nd generation of the g.GAMMAcap.
Bottom view of the g.SAHARA active dry EEG electrode.

g.SAHARA electrode is available with different pin lengths. This is very useful for different head shapes and hair thicknesses. For example, users with some hairstyles may prefer to use shorter versions at central regions and longer versions at parietal sites.

g.SAHARA electrode long pin and standard version.

BCI and dry electrodes

Brain-computer interfaces (BCI) usually rely on the P300, motor imagery or steady-state visually evoked potentials (SSVEP) measured with the electroencephalogram (EEG) to control external devices. The EEG is measured non-invasively with electrodes mounted on the human scalp using conductive electrode gel for optimal impedance and data quality. But the usage of gel has also some disadvantages: long montage time, abrasion of the skin and the need to wash the hair after the recording. The gel based EEG acquisition limits also the frequent usage of BCI systems on a daily basis. Therefore, a dry active electrode system was developed and compared to gel based active electrodes. Three subjects performed P300, motor imagery and SSVEP based BCI experiments. Evoked potentials, event-related desynchronization, power spectrum and accuracies were calculated for dry and gel based electrodes to compare them. The study showed that the new dry electrodes are able to pick up the corresponding frequency ranges of the EEG data for all three BCI approaches. The major advantages are that no extensive cap mounting time, skin abrasion, or hair washing are required. Nevertheless, dry electrodes are more sensitive to noise, movements of cables and electrostatic charges. Therefore a careful montage and a well controlled environment are important.

Complete system for Brain-Computer Interface experiments. Active dry eeg electrode system.

intendiX and g.SAHARA

The following video shows the montage of the g.SAHARA electrodes for a P300 BCI experiment. The P300 evoked potential depends on EEG activity in a frequency range of 0.1-30 Hz, and is therefore especially challenging for dry electrodes.


Available configurations

Electrodes and Sensors

product no.: 1079 read more g.SAHARAset 8, for g.USBamp — consisting of g.GAMMAcap²SET; 16x g.SAHARAelectrode (8x standard + 8x long-pin); 8x g.SAHARAclip; 2x g.SAHARAclipREF; 2x g.SAHARAclipGND; 1x g.SAHARAbox; 1x g.SAHARAboxCONNECTOR for g.USBamp; 2x adhesive mastoid electrodes (100 pcs.)
product no.: 1080 read more g.SAHARAset 8, for g.MOBIlab+ — consisting of g.GAMMAcap²SET; 16x g.SAHARAelectrode (8x standard + 8x long-pin); 8x g.SAHARAclip; 2x g.SAHARAclipREF; 2x g.SAHARAclipGND; 1x g.SAHARAbox; 1x g.SAHARAboxCONNECTOR for g.MOBIlab+; 2x adhesive mastoid electrodes (100 pcs.)
product no.: 1081a read more g.SAHARAset 16 (7 mm pins), for g.USBamp — consisting of g.GAMMAcap2SET; 16x g.SAHARAelectrode (7 mm); 16x g.SAHARAclip; 2x g.SAHARAclipREF; 2x g.SAHARAclipGND; 1x g.SAHARAbox; 1x g.SAHARAboxCONNECTOR for g.USBamp; 2x adhesive mastoid electrodes (100 pcs.)
product no.: 1081b read more g.SAHARAset 16 (16 mm pins), for g.USBamp — consisting of g.GAMMAcap²SET; 16x g.SAHARAelectrode (16 mm); 16x g.SAHARAclip; 2x g.SAHARAclipREF; 2x g.SAHARAclipGND; 1x g.SAHARAbox; 1x g.SAHARAboxCONNECTOR for g.USBamp; 2x adhesive mastoid electrodes (100 pcs.)

See some related products

Electrodes and Sensors

read more g.Electrodes: Specs & Features — various active and passive electrodes for electrophysiological recordings
product no.: 1023 (s, m, l) read more g.GAMMAcap² — electrode cap with 74 standard and 86 intermediate positions; extended 10/10 system
product no.: 1070a read more g.SAHARAelectrode, 7 mm — dry electrode, standard version, 8 gold-alloy coated pins with 7 mm length, 19 mm diameter, clip connector on top to connect to g.SAHARAclip, color: orange
product no.: 1070b read more g.SAHARAelectrode, 16 mm — dry electrode, long-pin, 8 gold-alloy coated pins with 16 mm length, 19 mm diameter, clip connector on top to connect to g.SAHARAclip, color: orange
product no.: 1071 read more g.SAHARAclip — active clip connector for use with g.SAHARAelectrode, 125 cm lead, 2 pin safety connector, color: orange
product no.: 1072 read more g.SAHARAclipREF — active clip connector for use with disposable adhesive mastoid electrodes, 125 cm lead, 2 pin safety connector, color: blue
product no.: 1073 read more g.SAHARAclipGND — passive clip connector for use with disposable adhesive mastoid electrodes, 125 cm lead, 2 pin safety connector, color: yellow
product no.: 1075 read more Adhesive mastoid electrodes — disposable adhesive mastoid electrodes, diameter 24 mm, 50 pcs, for use with g.SAHARAclipREF and with g.SAHARAclipGND, no gel remains on the skin after use

Hardware and Accessories

product no.: 1074 read more g.SAHARAbox — power supply & driver/interface box for 16 g.SAHARAelectrodes, for usage with all g.tec amplifiers, frequency range 0.1 Hz - 40 Hz
product no.: 1076 read more g.SAHARAboxCONNECTOR for g.USBamp — connector cable to connect g.SAHARAbox to g.USBamp, 16 channels
product no.: 1077 read more g.SAHARAboxCONNECTOR for g.MOBIlab+ — connector cable to connect g.SAHARAbox to g.MOBIlab+, 8 channels (EEG version)
product no.: 1078 read more g.SAHARAboxCONNECTOR for g.BSamp — connector cable to connect g.SAHARAbox to g.BSamp, 16 channels (monopolar)