measuring the phase of single point

[pramodsuper@gmail.com]

HI,

I am using pci 5154 digitizer.I am acquiring the pulse from some system where i will get only peak amplitude from this pulse .Now my task is i need to measure phase of the peak amplitude  with respect to sine wave from supply ie 50 hz.Like if one peak detected when sine wave is 90 i have to show peak amplitude  phase as 90 degree,consider i have got 3 peaks point in single sine wave at 30 degree,60 degree,120 degree i need to show peak point phase as 30 degree,60 degree,120 degree.How i can accomplish this task.Kindly help me .

I am also attached details of this issue in doc.

[DFGray]

This is a fairly straighforward problem, although the details may get tedious.  Try the following:

1. Acquire your sine wave and peaks on two separate channels.
2. Determine the phase of your sine wave at the start of your data set.  There are several VIs that will do this for you (e.g. Extract Single Tone).
3. Find your peaks in the other channel.  Once again, there are several VIs to do this.
4. Using the period and initial phase of the sine wave, and your acquisition rate, calculate the phase of the peaks.

Good luck!

[pramodsuper@gmail.com]

Thanks for reply.

I have another question.I have to  find the maximum peak of the  pulse.Each pulse may contains so many amplitudes but i need to find maximum amplitude in that pulse .I cannot use "thresholed voltage" option in "peak VI" because the same complete pulse amplitude may decrease in next acquisition. I have attached documnet explaining clearly. 

[DFGray]

Sorry for the late reply.  I just returned from a two week "vacation" (backpacking trip with Boy Scouts).

Since you know the phase and period of your signal from the previous algorithm, you can take a subset of the signal which only includes a single pulse.  Find the max and/or min signals in that subset and you should be good.  You can use the array max/min VI by itself or use it as a starting point to get three or five points which are used with a curve fit to give sub-sample accuracy.

If you need more info, let us know.  Good luck!

[pramodsuper@gmail.com]

Initially i have used "PEAK VI'  to find the peak of pulse but it will detect all the peak in a pulse,i cannot use "THRESHOLED VOLTAGE" option in peak VI since whole pulse may decrease in magnitude but still structure of pulse is same  .      Since i cannot use "PEAK VI'  i cannot able to find phase also sine i used "LOCATION" terminal in "PEAK VI".

I am novice in LabVIEW.

I have attached the VI and SUB VI what i have made for some application.Can you please verify and modify to find maximum peak and its phase with respect to sine wave .

It will be great help for me.

Thanks And Regards

Pramod