Experiments of DC human body resistance I: Equipment, setup, and contact materials

Direct Current (DC) applications have become more prevalent in recent years, primarily due to the increased usage of renewable energy and energy storage systems. A review of the existing safety standards and other literature shows that there are limited experimental data on DC human body resistance. In particular, no information was found by the authors describing the repeatability of DC body impedance and the effect of contact material and other variables. The experimental work described here investigated DC human body resistance and the effects of electrode contact material, wet or dry conditions of the skin, and the repeatability of body impedance for a given set of test conditions. Three male adult volunteers participated in this study; each volunteer completed twenty sets of experiments, with each set including four different combinations of test conditions. The results show that the electrode material has an influence on the measured body impedance when the voltage was less than 15 V, supporting the supposition that the observed nonohmic behavior is attributable to Schottky effects. The variability of the tests (measured by the use of the coefficient of variance) is higher at lower voltage and drops as the voltage increases. Wet conditions were found to provide more consistent test results than dry conditions. Due to the improved measurement consistency and its lowered impedance relative to dry conditions, data under wet conditions are preferred for further analysis. The time of day at which measurements were taken was also observed to have an effect with at least one of the test subjects.