Discussion: Figure 1 shows a waveform of the current from an ESD simulator into a large plane of metal as sensed by a Fischer F-65 current probe. Notice the "hash" that starts about 7 nanoseconds before the ESD current waveform and gives the waveform a rough appearance for the first few tens of nanoseconds. In addition, digitizing noise in the scope also contributes to the slightly rough appearance on the tail of the ESD generated current. This scope is an older one and newer scopes are generally better in both respects. But what can one do if noise contaminates your waveform?

If the contaminating noise is not related to the desired waveform, and if the desired waveform is repeatable, then using a scope's averaging function can substantially clean up the waveform in many cases. This is illustrated in Figure 2 which shows the discharge current of Figure 1 but using an average of eight individual waveforms. The noise on the waveform from both sources is substantially reduced.