Simultaneous variation of inter-electrode potential and impedance

Measurements were made of the simultaneous variation of potential and impedance across pairs of Ag-AgCl electrodes, while step changes in pressure were directed at developing procedures for reducing movement artifacts from surface electrode biopotential recordings of ambulatory subjects. Electrodes were applied to the arm with electrode paste. Impedance was measured at 10 kHz. Bandwidth of potential and impedance signals was limited to 0.05 to 30 Hz. Pressure changes were produced by releasing and retrieving a weight (150, 300 or 450 g) attached to a plate into which electrodes were embedded. Computer control of the weight allowed signal averaging of successive trials. Variation of interelectrode potential on the order of 1-20 mV and interelectrode impedance changes on the order of 10-200 mΩ were typical. Variations from subject to subject and within one subject over time were evident