Finding the exact peak of an sine wave

Klaus Kragelund · 2006-10-04T22:14:38+00:00

HiI have to do a phase delay measurement between a voltage and a currentsine wave.The current is delayed after the voltage and one way to find the phasedelay is to trigger on the zero-crossing of the individual signals.However it is an inductive motor load, so at low line voltages thewaveform of the current is highly distorded (un-linear zero-crossing).So I'm looking at perhaps finding the phase by finding the exact peakof both the voltage and current sine wave. The problem with that isthat the waveform is quite flat at the top (nature of the sine), so itis difficult to find the exact peak point.My idea to combat this would be to find the peak by continouslycalculating the dI/dt of the current signal. So at the rising of thecurrent I will get a time for the point of a certain dI/dt and at thefalling slope of the current I will again trigger on the same dI/dt(with negative sign). So the peak is just the two triggers added anddivided by twoBut, is there a better way than this to finding a trigger point on asine waveform? Anyone got experience with this?(I have ADC, comparator and opamp available for the job including lotof computational power)ThanksKlaus

Oct 04, 2006 20 Replies

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Hans-Bernhard Broeker 19 years ago

It's not a DSP term. It's just a bit of short-hand for "use a numerical optimization technique to maximize...".

Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de) Even if all the snow were burnt, ashes would remain.

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Finding the exact peak of an sine wave

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