Can we use the BioSemi active electrodes without paste ?
No, the BioSemi active electrodes are intended to be used with electrode paste. However, since the signal is buffered on the electrode, nearly all interference problems associated with high, and differentiating electrode impedances are eliminated. Therefore, skin preparation (cleaning with alcohol, rubbing etc) is never needed with active electrodes.
The lower limit of the noise level in bioelectric measurements is determined by the thermal noise of the impedance of the electrodes. Consequently, to achieve noise levels in the uV range, electrode impedances lower than 100 kOhm are required. A dry electrode operates either capacitively, or by using perspiration as a substitute for electrode paste. The last solution is not reliable, the first solution is practically impossible. A 100 kOhm impedance at 10 Hz would mean that the skin-electrode capacitance would have to be in the order of 100 nF (see diagram below). Because of the irregular surface of the skin, such high capacitance can not be attained by just pressing metal electrodes on the skin. Therefore we do not believe in the concept of a dry electrode for high quality bioelectric measurements, and as a result we do not offer such an electrode.