Phase Difference

[SparkEE]

I am not sure how to go about this but I have 2 analog inputs and am trying to find the phase difference. The issue is that I am not sure how to separate the two signals to compare them to each other. I am using Labview 7.1. Any help is greatly appreciated.

Thanks,

SparkEE

[WenR]

Hi SparkEE

I do not know if this is what you are refering to, but have you tried using the Split Signal VI?

http://digital.ni.com/public.nsf/allkb/01AB60FA9A4EDA1B86256D1A004ACB63

This thread has a similar question as well

https://forums.ni.com/t5/LabVIEW/How-do-I-split-3-signals-that-are-produced-by-a-DAQ-assistant/td-p/...

Cheers!

WenR

[SparkEE]

I have tried the split signal but then the question is how do I run the Case Structure simultaneously so that the phase difference can be measured. How does the FFT know to find the phase difference between the 2 analog inputs?

[SparkEE]

So I tried using the "SVT Gain and Phase" VI and was able to compare the 2 acquired signals but they are about 180 degrees out of phase. Is this due to how the data is acquired thru labview? if thats the case, do I just subtract 180 from the results?

[The_Right_Choice]

Hey SparkEE, 

This looks like you are using the Sound and Vibration toolkit, is this correct? Also, what hardware are you using? Im wondering all this because when I try to open your VI, it starts looking for files that I do not think I have installed on my computer. And regarding the phase question, it may depend on the hardware and your setup, especially with timing. 

[SparkEE]

Yes, I am using the sound and vibration toolkit 3.0

Hardware being used is the NI-PXI-4461. It has simultaneous analog inputs.

What VI's are you have trouble with? maybe I can upload them

[JÞB]

LabVIEW 7.1 is pretty ancient and I don't have the SVT installed but,  You are seriously abusing the Dynamic Data type conversion and that may be part of your problem.

Get rid of that for loop and just configure the From DDT like so...

[SparkEE]

Hey Jeff,

The reason "Single Waveform" is being used instead of "1D Array of Waveform" is because there are 2 analong channels in the DAQ Assist. Using "2D Array of Scalar" will not work either because the signal flows into "Scale Voltage to EU.VI" which does not accept arrays, it requires waveforms.

I am open to any and all suggestions 😃

[JÞB]

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@SparkEE wrote:

Hey Jeff,

The reason "Single Waveform" is being used instead of "1D Array of Waveform" is because there are 2 analong channels in the DAQ Assist. Using "2D Array of Scalar" will not work either because the signal flows into "Scale Voltage to EU.VI" which does not accept arrays, it requires waveforms.

I am open to any and all suggestions 😃

---

No it accept a 1D array of waveforms - which is exactly what you get out of your for loop!  (or my de-Rube-Goldberged- version)

[SparkEE]

My apologies Jeff, you were correct. I re-checked everything and the reason I believed that not to work is bc on my magnitude graph there was only 1 frequency response. I check my inputs and the 2nd input somehow got unplugged.

However, my issue with the phase difference is still unresolved.