Dependence of current and induced voltage due to spark discharge on gap length

The dependence of currents and induced voltages due to spark discharges for the neutralization of charges on a charged matter on gap length was measured by using brass disks as a ESD model. For the measurements, a grounded part was composed of a brass sphere electrode and a brass disk. A current sensor was fitted between the brass sphere electrode and the grounded brass disk. To detect spark currents due to the neutralization of charges between the charged disks, carbon loaded rubber strings for grounding and charging were used to suppress currents through wirings at the occurrence of spark discharges. From this experiment, the peak and maximum time rate of change of spark currents decreased with gap length. A spark current equation derived from spark current resistance almost coincided with measured currents for the gap length of 0.2 and 0.7 mm among the measurements for the gap length of 0.2, 0.7, 1.2, 2.35 mm. The induced voltages on a load of a loop antenna which was positioned at a distance of 10 cm from the discharge point decreased with gap length and those calculated by using an electric dipole model almost coincided with those obtained by measurements