Phase shift of a sine wave and a square wave

Hi,
I would like to simply compute the phase shift between a sinusoidal waveform and a square one. Between two sin-s I can compute, but I have no idea how to do that with a square waveform.
Thanks,
Ussr123

Hi there,
the easiest way is to use the ExpressVIs.
But you are only allowed to use the ExpressVI "Tone Measurements" if you have enough periods of the square wave, because it computes the phase with FFT.
An other possibility is to use the spectrum analyser VI as used in the attached exsample.
Greetz
Branni
Attachments:
Phaseshift_Sqr_Sin.vi ‏89 KB

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I am continuously acquiring two sinusoidal signals from the analog inputs of a daq card and saving the samples of the two signals into two different float type arrays. Can anyone tell me that how to calculate the phase shift between these two signals and as well as the peak voltage of the two signals? Please expain me with the help of an example code.
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Hi AI S
I have gone through the example of phase diff e.g and i have written the following code but when i run it , it gives the max value of 1st sine wave (outarray1) nearly equal (i-e 7.7 volt ) but it should be 8 V pk.
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Here is my code
double outarray1[8192],outarray2[8192] ;
double *peakLoc, *peakAmp, *peakDeriv;
    int count;
static double wave1maxval = 0.0;
static int wave1maxind = 0;
static double wave2maxval = 0.0;
static int wave2maxind = 0;
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PeakDetector (outarray1,8192,0.0, 3, 0, 1, 1, &count, &peakLoc, &peakAmp, &peakDeriv);
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        wave1maxind = peakLoc[0];
        wave1maxval = peakAmp[0];
SetCtrlVal(panelHandle,PANEL_wave1maxind, wave1maxind);
SetCtrlVal(panelHandle,PANEL_wave1maxval, wave1maxval);
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        FreeAnalysisMem (peakLoc);
    if (peakAmp)
        FreeAnalysisMem (peakAmp);
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        FreeAnalysisMem (peakDeriv);
    PeakDetector ( outarray2,8192,0.0, 3, 0, 1, 1, &count, &peakLoc, &peakAmp, &peakDeriv);
    if (count>0)
        wave2maxind = peakLoc[0];
        wave2maxval = peakAmp[0];
SetCtrlVal(panelHandle,PANEL_wave2maxind, wave2maxind);
     SetCtrlVal(panelHandle,PANEL_wave2maxval, wave2maxval);
    if (peakLoc)
        FreeAnalysisMem (peakLoc);
    if (peakAmp)
        FreeAnalysisMem (peakAmp);
    if (peakDeriv)
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    phasediff = fmod (phasediff, 360);
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Phase shift between a pulse and sin wave

Hello,
I was wondering if there is any VI that I can use to get the phase shift between a pulse and a sin wave (they have same frequency).
The Ideal case is that the pulse should go to 1 when sin wave is positive and goes to 0 when the sin wave is negative. I want to set this test to measure the phase shift between pulse going to one and sin wave going positive.
We just bought labview full version with Signal processing package, and I was wondering if there is anything that would be useful for me.
Thanks in advance,
Baran.

Hi Baran,
Try this on for size and see if it works for you.
Have a great day,
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Attachments:
Phase Difference.vi ‏22 KB

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I am using a Labview VI to control an array of servo motors, each receiving a sine wave input (with different phase offsets for each servo). I'm using a NI USB-6229 DAQ system to monitor their movement via a wire that I've soldered onto each servo's potentiometer. I've written another VI that recieves both the initial sent signal and the returned DAQ signal and plots both on a waveform chart. Both signals show up on the plot as expected, with an obvious phase shift between them. I'm having problems accurately measuring the phase shift, and I'd rather have an automatic method that gives accurate numerical values instead of a more qualitative visual method.
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Since I work with lock-in amplifiers I came up with this. I guess it will work in your case. This method has some limitations. It will work up to 180 degree. It also measure absolute phase lag. You can not say if the signal is leading or lagging. But in your case it will always be lagging. I posted a VI showing the method in another discussion. Here is the link. http://forums.ni.com/ni/attachments/ni/170/409516/1/demo_v2.vi. Since your DAQ unit do not have simultaneous sampling you will get a small phase error due to inter-channel delay. This is also true if you use the FFT method. What is your signal frequency and which samplerate do you use?
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Have you done the basic physics and mathematics? For the speed of sound = 343 m/s and the frequency = 40 kHz the wavelength is 8.6 mm. At 40.001 kHz the wavelength is 214 nm shorter.
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Message Edited by awais.h on 03-30-2010 11:20 PM
Message Edited by awais.h on 03-30-2010 11:21 PM
Solved!
Go to Solution.

Hi
Thanks for the code but I'm afraid it won't work. Like you said the probability of choosing a value that is on both graphs may not happen. This is something that I would like the code to do automatically.
But I did use the previous code posted and made some modifications to it and it seems to work perfectly. Now the next thing is to be able to get just that one value that tells you the first time difference.
Here is what I get using that code.
As you can see from the t Values. I only need the one that is highlighted. If there is a way to filter out the rest it would be great.
I was thinking of a while loop and as soon as the value is higher than 3E-5 it would store the number and stop the loop, but I'm not too familiar with arrays in labview.
Here is the the code modified.
As you can see, it wasn't that big of a modification and it still is your code.
I will keep trying.
Thanks for the help
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FinalShockSpeed.vi ‏55 KB

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RiversDaddy wrote:
... currently I am doing it by looping and reducing the error towards zero to fit the amplitude and phase. (I know the frequency). If this is what you are looking to do then I will help, or should I be doing things differently? All of the functions I have found to filter or extract tones seem to introduce a larger frequency of phase error than i get using this method, but am I missing something?
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Message Edited by Jaime F on 02-06-2008 11:42 AM
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Hello, Rilee,
Thank you very you very much. But I am still confused. The website I can not open. As you said, I shall create a data array to contain three phase data, for example, sinedata[750], sinedata[0:249] contains first AO, and sinedata[250:499] the second, and the rest is the third. then
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Phase shift of a sine wave and a square wave

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