Calculate Phase from Noisy Sine Input

Question

Hello,
I have a sine wave being read in real time into my VI and I'd like to calculate how out of phase it is with a simulated sine wave. I followed the example on http://digital.ni.com/public.nsf/allkb/F4BB644ECCA​595D886256FFE00722E29 and the phase is still all over the place and I'm assuming it's not being estimated correctly. The simulated sine I'm comparing it to is from Sine Waveform.vi with a constant phase.
These calculations worked when I had two simulated sine waves for testing. Any insight on what I should do is much appreciated.

Answer 1

First you need to define what you want to do.
1. There is no meaningful definition of a phase relationship between two signals of different frequencies.
2. The way you create subsets of the signal data makes it almost certain that the phase returned by Extract Single Tone Information.vi will differ on each iteration.
The graph image shows the first part of the signal passed to Extract Single Tone Information.vi on two successive iterations of the for loop.  Whilethe difference is not large, it is clear that the initial phase of the two signals has changed. The array image shows the outputs of Extract Single Tone Information.vi for the 60 Hz signal and for the distorted signal. Note that the frequency of the signal is not 60 Hz and that it varies slightly from iteration to iteration. The phase shows approximately a 22 degree progression with each iteration with some variabillity probably due to the changing frequency.
Lynn