Référence de phase de la fonction "Extract single tone information"

Bonjour !
J'utilise actuellement la fonction "Extract single tone information" pour calculer la phase d'un signal acquis avec un DAQ 6211. J'aimerai donc savoir quelle est la référence pour calculer la phase du signal ? J'ai ouvert la fonction et les sous VI qui la compose mais je vous avoue que la compréhension de cette fonction dépasse mes compétences (je suis étudiant à la fac en L3).
J'utilise notamment cette fonction pour réaliser un phasemètre donc j'ai récupéré la phase de 2 signaux déphasé (par l'intermédiaire d'un DAQ 6211) avec cette fonction et j'ai soustrait "phase2-phase1" pour avoir le déphasage, mais le résultats rendu est tantôt une valeur "phi", tantôt "phi-360".
Merci par avance de vos réponses !

Bonjour,
Pour vous aider à utiliser le VI "Extract Single Tone Information", vous pouvez consulter les exemples qui permettent d'illustrer le fonctionnement du bloc dans son contexte.
La localisation de ces exemples se situe dans l'aide (tout en bas). Voici le lien direct : Extract Single Tone Information VI
Cordialement,
Jérémy C.
National Instruments France
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Similar Messages

Using Extract Single Tone Information to detect phase

Dear all,
I have problem using Extract Single Tone Information vi to detect phase angle of a sine wave.
I posted similar question a few days ago regarding using the same vi to determine phase angle of a square wave and realised it couldn't be done because square wave is not single tone. I modified my program slightly and use it to examine a sine wave but I still couldn't get reliable results.
Please find the attached for the program code. When I set frequency to 5 Hz, everything worked fine but when I set it to 5.17 Hz with 20 degree phase, the detected phase value keeps changing. Appreciate if you could help me on this matter. Thank you very much!
Best regards
Attachments:
SineWavePhaseAngleTest.vi ‏28 KB

Hi looloo,
Sorry for slow response! Here's the VI back-saved to LV8.2
(in case It's not too late to help...)
The "phase" output reflects the "angle" associated with the beginning value in the Y-array (when Y = amplitude, Phase is 90deg.)
Phase is changing because sine-wave (Y-input) is shifting each time single-tone is called...
Cheers!
"Inside every large program is a small program struggling to get out." (attributed to Tony Hoare)
Attachments:
SineWavePhaseAngleTest[1,LV8.21].vi ‏38 KB

Extract Single Tone Information - phase step

Hello!
I am using Extract Single Tone Information to measure amplitude, frequency and phase of a slowly varying signal.
But sometimes the phase jumps ~350 degrees for no apparent reason. I have made a small vi (in LabView 8.5 professional) to demonstrate this, see attachment.
Seems like the shift occurs when the ends of the input signal cross each others level, in opposite directions.
Guess I should start looking for an alternative method for doing the measurements.
Any suggestions or ideas are most welcome.
Attachments:
phase_test.vi ‏30 KB

Hi Thomas
It jumps 360 degrees to be exact. -180 degrees and +180 degrees is basically the same thing so the phase you are seeing is correct. It does not look very good in a chart though. To improve the looks you can use the subVI called "Unwrap phase".
Regards
Øyvind Ø

Phase-in/phase-out profiles data extraction to SAP BW

Hi All,
I am working on extracting Phase-in/phase-out profiles data from APO to BW for reporting purposes. I came across a table
/SAPAPO/FCST_LC1 in APO system which has this data and the Idea is to use Generic data source on top of this table and extract it to BW.
But i am looking out for any possibility of this being done using any standard data source. I need pointers from anyone who have worked on extracting this data.
Is there any standard datasource , planning object , BAPI on this?
Any help is appreciated.
Thanks,
Satish

Hi,
The datasource 2LIS_17_I0NOTIF - Notifications needs to be installed from RSA5 and activate in RSA6 in R/3 side.
You should be able to see green lights in LBWE in R/3 side.
Then, in BW side, RSA1>Install from Content> Cube
Hence, your Cube with entire dataflow will be installed and activated in BW system.
To load data, you have to fill setup tables in R/3 side and init with data transfer in BW side. This will bring all the history data and your subsequent delta will be regularized in BW.
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Extraire une fréquence précise d'une FFT

Bonjours,
Voila ma question, J'ai effectué une FFT sur un signal temporel échantillonné à 1024 S/s , j'ai donc tout mon spectre de 0 à 500Hz, maintenant j'aimerais en sortir l'amplitude à 50Hz +-3Hz (ceci afin de voir la contribution du réseau électrique dans le spectre de mon signal mesuré) et je ne sais pas vraiment comment m'y prendre, iest-ce qu'il y a un vi déja existant qui fait cela?
J'ai essayé d'utilisé le vi "Multiple Tone Exctract", cela marche mais je le trouve un peu lourd pour mon besoin.
Cordialement
Sébastien Kuenlin
Résolu !
Accéder à la solution.

Bonjour et merci d'avoir posé votre question sur le forum NI.
Effectivement un VI Express tel le "Multiple tone extract" est gourmand, c'est pourquoi il est possible d'utiliser la fonction "Extract Single Tone Information", de plus bas niveau, comme dans l'exemple proposé ci-dessous et en pièce jointe.
En espérant avoir répondu à votre question.
Mathieu TUR
National Instruments France
Mathieu_T
Certified LabVIEW Developer
Certified TestStand Developer
National Instruments France
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Pièces jointes :
Mesure d'un ton.vi ‏28 KB

Waveform measurements - info needed

I am fairly new to LabView and am trying to understand some of the vis in the Waveform Measurements and Analyze folders. Help with any of the following questions is appreciated.
1) What is the phase output of the Spectral Measurements Express vi? I've seen several examples using this function and none of them use the phase output. If I put in a simulated sine wave with no phase offset, the FFT phase output is -90 deg at the input freq.
2) What is the amplitude output of the Tone Measurements Express vi? It looks like average peak value over the duration of the signal, but I'd like to be sure.
3) If I get a value of 28.42f at the "detected phase" output of the Extract Single Tone Information vi, what does the "f" mean?
4) Is there any information about the details of these functions? The information in the Help window is scant, the tutorials provide a lot of theory, the examples don't always cover what I want to know. Is there somewhere that provides a fuller explanation of the inputs and outputs of the functions?
Thanks in advance,
Margaret

Hi Margaret,
In response to question 1, the Spectral Measurements Express VI is used for FFT-based measurements, and the Tone Measurements VI is used to find the frequency or amplitude of a specific signal. Have you tried viewing the Detailed Help for these commands? These can be viewed by right-clicking on the command, choosing Control-H to bring up the Context Help, and clicking Detailed Help. This will allow you to view Examples and detailed information on the inputs and outputs.
Here is some detailed information about the Spectral Measurements Express VI from the Help:
FFT-based spectral computations assume that the finite block of
signal data represents one period of a periodic signal. The computed spectrum of
this effective periodically extended signal shows energy spreading into
frequencies that were not present in the original signal. To reduce this
spectral leakage, use smoothing windows to taper the sharp transitions in the
effective signal. You do not typically use windows if you can acquire an integer
number of cycles of each frequency component measured or if you are analyzing
noise spectra.
In response to question 2, the amplitude of the Tone Measurements Express VI returns the amplitude of the detected single tone in Volts peak (Vp).In response to question 3, what is the phase of the signal that you're measuring? I used this VI with a Simulate Signal VI and simulated a sine wave and was able to correctly use the Extract Tone VI for all phases. Have you tried doing this?
Also, here is the manual for the Spectral Measurements Toolkit. Let me know if you have any more questions.
Amanda Howard
Americas Services and Support Recruiting Manager
National Instruments

I have doubt in measuring magnitude and phase of a waveform

I am not sure which block I should use instead of "Frequency Response Function"
Attachments:
first.vi ‏54 KB

It depends on what exactly you want to achieve. If you are interested in the transfer function between 2 signals, then, as Tim mentions, the FRF VI is the one to use. However I notice in your example that you only have one signal and that signal is periodic. Are you interested in the Amplitude or RMS value of that single signal as well as the start phase of it? If yes you should condiser using the Extract Single Tone Information also located in the same palette.

Phase difference analysis question

I know there are a lot of signal processing experts on this board and wish I could get some nice suggestions.
I have a two channel data: one is the load signal like sine wave; the other is the response signal with a pulse in each load cycle. I am going to analyze whether there is phase shift for the pulse to the load signal. Visually it is very straightforward to "measure" the phase between load peak and pulse peak. But it's hard to code it. I believe there are a bunch of better ways for coding easily (I am considering cross-correlation). Since these are high frequency signals, the size of the data set is huge, which makes such processing time-consumming.
Any suggestions? Thanks!!!

I find the answer in the help. Thank you very much! Jay
Extract Single Tone Information 1 Chan.vi
"Takes a signal in, finds the single tone with the highest amplitude or searches a specified frequency range, and returns the single tone frequency, amplitude, and phase. You can use this polymorphic VI to analyze a waveform or an array of waveforms. "

Looking for a VI to calculate phase difference

I am looking a VI that will calculate the Phase difference as a function of time between two sine waves at 20 kHz. I am using LabView7 Express just so we're on the same page.

Hi,
There is a Extract Single Tone Information.vi that is available from All Functions >> Analyze >> Waveform Measurements. This VI takes a time signal in and returns a detected phase (deg) out. Therefore, you can use one of these VIs for each sine wave and take that difference to determine the phase difference of your sine waves as a function of time.
Note that the Extract Single Tone Information.vi is not available LabVIEW Base package, but is available in all other LabVIEW packages.
Thanks again and have a great day!
Kileen C.
Applications Engineer
National Instruments

Waveform phase detection

Hello!
I have a problem with a block called Extract Single Tone Information.vi. I am trying to detect the phase difference between two sinusoidal signals which have a slightly different frequencies. How does this block calculate the phase of the signal (rising edges or zeros of highest detected amplitude or what)?
Thank you!

Hi!
Have you seen (see the attached doc version) its implementation? You can also do it custom without using the exctractor.
B.
Attachments:
screenshot.doc ‏172 KB

Calculate Phase from Noisy Sine Input

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/F4BB644ECCA595D886256FFE00722E29 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.

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

Phase calculation

I would like to know if there is a SubVi that calculates the angle phase between two analogical signals (or waveforms). If answer is negative, how could I do it in an efficient way?.
Thank you!.

For the phase difference to make sense, your signals have to either be periodic and share a common fundamental frequency or at least be very "similar" with the one being more or less a delayed version of the other one (this would for example be the case if you only have a sub-period duration of your signals)
In the first case you can for example use the VI "Extract Single Tone Information.vi" located in your Analysis>Waveform Measurements palette. The VI will return the detected fundamental frequency (make sure you get "almost" the same result on both signals), and the start phase of that signal. Then simply subtract the two phase values to get your result.
If your signals are not periodic (that is do not show a common fundamental frequency), then you may
still be able to extract a good estimate of the time delay between them. Use the Cross Correlation function. The peak value position of your result with respect to the center is a good estimate of the delay. To get your result converted to a phase difference you still need a signal frequency (that you hopefully know from your system)

Phase instability?

Hellow!
I am trying to measure the phase angel of a simple sine wave from a osilloscope,i use "extract single tone information.VI" which give me the phase information of the signal,but to my disappointed,the phase result is always shifting.I am sure that the signal is stable,because it is from a function generator.so are there any reason that the phase is shifting so much? i notice that the the other two out put from "extract single tone information.VI " is much more stable.
Thanks!

Well, we need to know if the phase of your analog signal is changing (likely) or if the "extract single tone information.VI" is faulty (unlikely).
What happens if you display your signal on a graph indicator. Does it seem to scroll or does it look locked? Phase is quite meaningless without a reference point.
Have you tried testing your code with the "simulate signal" express VI to eliminate the external hardware?
LabVIEW Champion . Do more with less code and in less time .

How can I output frequency readings of my signals using FFT?

Hi there, I need help in regard to the topic stated.
Currently I have accquired a sine wave with frequency that vary, using one of the accquistion card by NI. I had converted it to a digital signal so that labview can read it. Now, I will like labview to output the measurement of the frequency.
For example : sine wave of 5KHZ is accquire , labview will use FFT to convert time domain to frequency domain, and then output the frequency of the sine wave, in the case, 5KHZ.
What function block should I be using? I had explored the function blocks of all FFT. Most of them output either real FFT, complex FFT, magniture or phase. But none of them output the reading of the frequency.
Maybe I had missed out some function block, so how do I go about output a frequency reading after using FFT?
Thanks a lot in advance.

After Converting your signal from time domain to frequency domain, u cant expect there is only one frequency component,they should have different frequency components according to your input signal.Use extract single tone information to get the output reading of the frequency.
Balaji PK (CLA)
Ever tried. Ever failed. No matter. Try again. Fail again. Fail better
Don't forget Kudos for Good Answers, and Mark a solution if your problem is solved.
Attachments:
Detect Freq.vi ‏15 KB

Measuring the frequency using PCI 6221 Daq card

Hi
I want to find the frequency of an external signal.
How can i do that give me some idea or example.
Regards,
Hari

If you need to capture the waveform look at the aquire waveform examples and add the
Extract Single Tone Information VI
Owning Palette: Waveform Measurements
VIs
Requires: Full Development System
Takes a signal in, finds the single tone with the highest
amplitude or searches a specified frequency range, and returns the single tone
frequency, amplitude, and phase. The input signal can be real or complex and
single-channel or multichannel. Wire data to the time signal in
input to determine the polymorphic instance to use or manually select the
instance.
(copied from the help)
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Référence de phase de la fonction "Extract single tone information"

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