The electrodes for surface recording of biopotential are generally made of silver-silver chloride (Ag-AgCl). This disposable foam-pad consists of an Ag-AgCl metal contact button at the top of a hollow column that is filled with a conductive gel. Most bioelectric measurements an interference level of 1 to 10μV peak-to-peak (pp) or less than 1% of the pp value of an ECG, is acceptable.