Second order statistics of Brownian motion: testing a digital noise spectrograph

Previously, the authors have presented a new digital noise spectrograph to determine the statistical properties of ionic Brownian motion. The new device, devoted to numerical signal analysis, gives the correlation function C(τ) of a series of τ values; the power spectrum is directly deduced from C(τ) in the whole frequency band. Results for different bands are obtained by numerical filters and compared with analogical ones. Results obtained by autocorrelation on a unique channel and cross correlation on the two channels are reported. Application to a NaCl physiological solution is given