  We have developed a new method for fabrication of ultra-low noise
silver-silver chloride (Ag-AgCl) reference electrode with dramatically high
stability, useful in biomedical precise measurements. Low noise level and high
stability are the most important features when evaluating reference electrode
for example when used as a half-cell at electrochemical cells. The noise was
measured for bare Ag-AgCl electrode pairs in a saline electrolyte without any
junction. The noise spectral density for such measurements increases at low
frequencies due to flicker (1/f) noise. Thermal noise from the real part of the
electrode impedance is always lower than 1/f noise and is shown as offset
voltage in noise spectrum. Electrode noise is highly correlated to its offset
voltage. Moreover, the variance of the potential difference in our measurements
is correlated to the noise level of electrodes. In this paper, offset voltage
spectrum and the variance of data while doing measurements are proposed for
identification of noise in our electrodes. The results presented suggest a new
process for fabrication of electrode pairs with differential noise potential of
16 nanovolt root mean square at frequency of 1 Hz.
