Sampling AC Signals: Comparison of Fitting Algorithms and FFT

Fitting algorithms and FFT are commonly used to determine the RMS value and the phase of AC signals. This paper focusses on metrology applications and compares different algorithms with respect to their uncertainty contribution. The study covers pure sinewave signals, signals with noise and signals with cross-talk from a power line. The results are experimentally verified using an AC Josephson voltage source. The paper shows that the DC performance of the sampling system can be used for AC signals. The uncertainty contribution of the algorithms is negligible if the algorithm is chosen carefully.