Abstract: Emitted light from a pulsed plasma system is detected, amplified and digitized over a plurality of pulse modulation cycles to produce a digitized signal over the plurality of RF modulation periods, each of which contains an amount of random intensity variations. The individual signal periods are then mathematically combined to produce a stable local reference waveform signal that has decreased random intensity variations. One mechanism for creating a stable local reference waveform signal is by subdividing each of the individual signal periods into a plurality of subunits and the mathematically averaging the respective subunits within the modulation period to produce the stable local reference waveform signal for the modulation period. The stable local reference waveform signal can then be compared to other instantaneous waveform signals from the pulsed plasma system, or waveform parameters can be derived using various signal processing techniques such as Fourier analysis.