Instantaneous measurement of electrical parameters in a palm during electrodermal activity

The determination of impedance can be performed by means of a frequency-domain analysis or a time-domain analysis. The latter has the advantage of being able to measure instantaneously all the frequency characteristics of impedance. The method is hence well suited to obtain the biological impedance which changes with time. An instantaneous method of measuring skin impedance, by using time-domain analysis has thus been developed. The fast Fourier transform (FFT) of the step response for current to the skin can determine the palm impedance. This method can carry out the determination of the parameters of the palm skin impedance during a galvanic skin reflex (GSR), which is impossible by means of frequency-domain analysis.