Phase angle values aren’t the same tia sal22

[sal22]

Phase angle values aren’t the same tia sal22

Greetings All

I created a test VI to see how to calculate and verify the phase difference between two generated signals.  It seems to work but the phase angle values are different if I put in 180 for phase slider 1 and 0 for phase slider 2 I get 151.1 degrees.  Am I doing something wrong (it should say 180)? Is this the right way to do this or is there a more efficient way to proceed.  I’m going to acquiring an audio signal on the left and right channel of my audio input and would like to measure the difference in phase.

Tia sal22

[sgregor249]

try this

[sal22]

hahahah I guess that fixed my problem but it really doesn't explain why the phase angle numbers don't match up.

[kaush]

@sal22 - Hello, I saw your VI and i am pretty much confused y u were not getting the proper phase difference.. Did u get the answer.. cos even i am struck with some phase angle calculations.

[sal22]

Nope never got an answer the last guy basically said to minus the two inputs a-b it wasn't even comparing the two output phases of the signal.  hahaahahaha but that doesn't do me any good if I'm comparing two audio signals  with unknown frequencies and phases. see pics that just don't make any sense.  Thought this would be simple....I guess not.....

[Cory_K · Accepted solution]

I tried to re-create this issue. It seemed to be a rounding issue.

Instead of 180 degrees, it would give anywhere between 160-200 degrees for the phase difference.

I found if you use a data type with more precision eg DBL, it helps.
Also, you could try rounding the phase at the at of the calculation.

You could see the attached example to see what I did.

[sal22]

Thanks That helped alot!!!  Here's a shot of the final Vi

Message Edited by sal22 on 07-30-2009 11:08 AM

[kaush]

Thanks for the update..

I am trying to draw frequency response (bode Plot) for my control valve. I am not getting the phase angle properly 😞 If u gusy have any idea please help me.

I am taking o/p from LVDT which is connected to control valve. I am using DAQ 6036E. Please see the attachments.