On the uncertainty in the current waveform measurement of an ESD generator

The uncertainty in the current waveform measurement of an electrostatic discharge (ESD) generator is evaluated. The measurands are the current amplitude and the rise time of the output current waveform of the ESD generator. An intuitively simple model is proposed to evaluate the uncertainty in the current amplitude measurement. Type A and Type B evaluations for all contributions to the measurement uncertainty are performed to obtain the combined standard uncertainty. The evaluated expanded uncertainty (95.5% confidence level) of the current amplitude and the rise time at ESD voltages of 2, 4, 6, and 8 kV are within the specification of IEC 61000-4-2. The results show that the uncertainty in the current amplitude measurement stems from the voltage reading of the measuring equipment, the difference between the displayed and the actual voltages of the discharge tip of the ESD generator, and the inaccuracy of the delta time measurement of an oscilloscope, whereas the uncertainty in the rise time measurement mainly originates from the measuring equipment.